Home Travel Stories Gas Logs 1969 PONTIAC GTO *Mongrel* Chev 350 LTI-4 bbl MPG= 14.8 Overall
1969 PONTIAC GTO *Mongrel* Chev 350 LTI-4 bbl MPG= 14.8 Overall PDF Print E-mail
Written by Double Dragon
Thursday, 30 December 2010 23:33

1969 PONTIAC GTO *Mongrel* Chev 350 LTI-4 bbl MPG= 14.8 Overall average


Writing and photography copyright D. S. Brown

Metric= 5.7 L engine- 15.9 L/100km overall average

Is it a 1969 GTO? The original 400 engine and bent frame are long gone. Do we list it as a 1972 LeMans? That's the source of the frame and cowl. Do we list it as a 1970 LT1 350 Corvette? That's where the drive train comes from.

Restoration guys will transfer the VIN of a rust bucket onto a rebodied car and consider the VIN to be the final word. This car is nowhere close to a restoration. It seems logical to call it by the year and model of body panels which was standard practice on drag strips at the time. Competitors would campaign the same car for several years simply by replacing fenders and other pertinent parts that changed with each new model year.

This car provides a glimpse into the street racing world of the 1970s and 1980s. Most of the common drive train and suspension performance modifications of the day appear on this car. This car experienced the typical fate of many original musclecars as they become quasi hot rods which were then thrashed to death. An interesting side note is that many of the habits and modifications made by street racers actually optimize MPG as discussed later in this story.

The first owner professionally built it up and kept the GTO for nearly a decade before allowing it to fall into the hands of amateur tinkerers. The first owner's quest for more speed induced him to tackle a pro street project which motivated the sale of the GTO.

After this, the owner history follows a pattern of young males who spent all of their time in the car, and all of their money on the car. Each owner contributed some speed equipment, but the GTO deteriorated from this point forwards. Each new owner lasted about two years and typically switched registration and insurance into his girlfriend's name after about 6 months of ownership when his insurance rates climbed sky-high due to tickets. After the inevitable loss of driving license, the car would be sold to the next hotshot.

VIN and insurance histories combined with a trunk full of parts and speed shop receipts, junkyard receipts, traffic tickets and old drag strip time slips fill in some of The Mongrel's hazy history. Former owners and friends of former owners plugged more gaps. A former owner was certain it was a 1969 Corvette engine, but mechanics who worked on it insist that it's a 1970 LT-1. This gives you an idea of the expertise level of most of the guys wrenching on their own cars in the street racing era of late 1970s early 1980s! No formal training, lots of word of mouth or learning by trial and error. A few of the guys were into car magazines and probably learned a bit more that way, and they all had money to burn on speed equipment.

Since most of the 1969 GTO sheet metal and interior was retained, we'll refer to it as a GTO. Below is a relatively early shot of the Mongrel on a road trip back when the body was still decent looking. The Endura front end was clean and properly aligned.


69 gto mongrel gas pumps

The Mongrel began life as a 1969 Carousel Red (non Judge) GTO that was rear ended. The GTO body, excluding rear end was grafted onto a 1972 LeMans hardtop chassis. The donor chassis VIN indicates a LeMans two door hardtop built Tuesday May 30, 1972. The Springfield Green car was a low horsepower 350 2 barrel bought by a 28 year old male. The bench seat car had power steering, power drum brakes with the basic 2.73 axle and TH350. The LeMans served as a winter driver whose function was solely to keep the 1969 GTO out of the salt.

When the GTO was written off, the LeMans became the foundation for a project using the remains of the GTO and a totaled Corvette. The reasoning behind a non Pontiac engine was that the recently built up LT-1 engine was faster than the tired old stock Pontiac 400. Back then no one cared about originality- just expediency and speed. Another factor considered was that after being seriously rear ended, the original GTO drive train might have problems. Driveshaft or transmission tail shaft may have become warped, engine mounts may have twisted etc.

Back in the late 1970s The Mongrel passed as a "Judge clone". By today's restoration standards, its light years away from being remotely authentic looking. Standing 20 feet away you spot 1971 dual racing mirrors off a LeMans Sport or GTO painted the same flat black as the hood scoops, but mounted onto the 1969 GTO doors, 1970 rear end with 1970 Judge deck lid and spoiler. The mix of years and parts looks good, but incorrect, hence the designation 'mongrel', not clone.

The various pieces of the car were painted Carousel Red to match the GTO parts. The front grille seems to be from a Judge, because it was blacked out like Judge grilles were. The hood came with the optional 1969 hood pins with the inside hood blanket stripped out to lighten it or avoid pieces of it from getting into the engine when the car was run on the strip without air cleaner in place. Judge stickers were added to the car. The original black 1969 GTO interior was installed along with a 1970 LT1 Corvette 350 that had been balanced, blueprinted and decked. Compression was raised so high that two batteries were required to crank it over. The cam was so lumpy that a pair of sunglasses placed on the dash pad would leap off due to the constant thumping and throbbing of the car at idle.

Racing electronic ignition system was added to a converted HEI system. Raise the hood and flip the switch on the firewall mounted control unit and the car could be adjusted for 'Street' or 'Strip'. Put the switch in the middle position and you had no ignition: a nice theft deterrent. A 4.33 positraction was installed along with 7 inch front and 9 inch rear real 14 inch aluminum mags. The chassis was converted to heavy duty suspension, Gabriel adjustable shocks, front and rear T/A sway bars and polyurethane bushings.

The Mongrel GTO was street raced in the late 1970s and most of the 1980s. As the owners changed, it was repainted and valuable OEM parts were stripped off while generic 'Day Two' performance items accumulated. The rear deck lid and spoiler were removed and replaced with a 1971 T37 lid. The 1971 Formula wheel was replaced with an aftermarket grant wood steering wheel. 1976 high back black Firebird seats replaced 1969 GTO buckets. Carpeting and rear seat were removed to save weight. The bare floor was painted black with a urethane coating.

The car bounced between upgrades and downgrades depending on whether the car had just been purchased or was about to be sold. Somewhere along the line in a pre-sale tactic someone stripped away the ram's head manifolds and switched them for passenger car exhaust manifolds. The open element Corvette air cleaner was switched with a passenger car item.

Sometimes the 'improvements' were in the eye of the beholder. Nowadays, a 1969 bodied GTO mated with its original 1969 dash would be a desirable combination. In a complex ploy to 'upgrade' the car, a new purchaser removed the 1969 GTO dash and switched it with a black 1970 GTO dash. The motive for all this work traces back to the original 1969 GTO speedometer which only reads to 120 MPH. The 140 MPH unit wasn't available until 1970. This owner wanted to have the 140 MPH speedometer but the 1969 dash pods aren't interchangeable with the 1970-2 dash. Out goes the whole dash!

The 140 speedometer was standard in 1970-71 LeMans and GTO models. You could still get one in 1972 although officially the speedometer had been lowered back to 120. At the start of the 1972 model run some 140 speedometers from the prior year were installed as factories used up the previous year's parts. The other way to get the 140 unit in 1972 was to order the optional gauge package which included the 140 speedometer.

The LeMans chassis base for the Mongrel GTO was built late in the model run without a gauge package and hence was fitted with a 120 speedometer just like the original 1969 dash. By this time, the 1972 dash was probably long gone anyways since it was green. Two 140 speedometers were piled up in the trunk, suggesting that someone bought them before realizing that they weren't interchangeable with the 1969 dash in the car. Once the dash was changed to a 1970 dash there was no need to pull out the existing speedometer. There were no 120 MPH speedometers amongst the parts in the trunk. The original 1969 GTO speedometer and the original 1972 LeMans chassis speedometer are both missing in action: true mileage is thus completely unknown.

The work done on the Mongrel GTO brings up an interesting point about the owners of Day Two muscle cars back then. Guys were actually willing to jump through complex hoops just to have a 140 speedometer instead of the 120 version. They would cut up the floor to install a four speed in an automatic car and fabricate new mounts. It was routine to pull a bench seat out and drill out the floor to suit the mounting points of a set of GTO buckets, then drill again for the different bolt pattern of 1976 Trans Am seats.

The amount of work kids were willing to do for status on the street was way out of proportion to the actual benefit. R and R of a whole engine over the weekend was a common occurrence back then. I remember a guy who put a ceramic clutch in his Dart over a weekend. He was using a thousand pounds more pressure in the plate than any human could hope to operate smoothly. When it came time to drive the car it almost impossible to shift the car at normal speeds on the street. Next weekend, out goes the transmission.

In a similar vein, I vividly recall a neighbor who seemingly spent his whole life lying underneath his Javelin squinting into a trouble light all night. The car was perpetually up on blocks. One particularly freezing freak blizzard hit. Around 2 A.M. there was a slight glow under his car almost obscured by the swirling blanket of snow. Sure enough, there he was at his post lying on the cold driveway. Nothing could deter these guys! Nowadays the same energy expenditure is used to return Day Two muscle cars to factory condition.

The LT-1 had bottom end wear, the solid lifters were in desperate need of adjustment, and the carburetor was shot. Despite these problems, the GTO was still a beast. A speed shop visit for headers, correct carburetor, open element air cleaner, headwork and major tune up had the car back in peak form. The four bolt bottom end was left alone, with the shop's assurances that it could easily soldier on. The car went through spark plugs at an alarming rate, but had no other issues.

The Mongrel GTO weighs less than a stock 1969 GTO or a 1972 LeMans. The AMA specs for a 1972 two door base LeMans hardtop establish curb weight at 3,329 lbs. A 350 2 bbl adds 216 lbs over the standard 250 six cylinder. Dual exhaust adds 28.6 lbs. Power brakes and steering add around 55 pounds. 3,629 lbs total is about what the LeMans weighed back when it came out of the factory in May, 1972.

The dual sport mirrors and Endura front end, and scooped hood add weight over the LeMans. Lack of inner side impact beams in the 1969 GTO doors probably balance this out. Sound deadener was removed under hood, undercoating scraped off underside, rear seat and carpet and underlay was gone leaving a bare metal black painted floor.

There was no console or radio and the Grant steering wheel may have saved a pound or two. The 350 engine weighs less than the stock Pontiac 400. The LT-1 weighs less than the old LeMans 350 due to aluminum intake and headers instead of iron manifolds. The flex fan and aluminum radiator shave a few more pounds. The mags save a significant amount of weight.

The oversized tires at rear add some unsprung weight, as do chrome lug nuts and locking wheel nuts. Weight adds up from two large sway bars with rear traction bars, heavy duty springs and shocks. Under hood weight accumulates from bulky inner fender mounted aftermarket ignition booster system, two batteries, an air horn, heavy duty alternator and under hood lights for night time tinkering. Inside the car a tachometer and aftermarket gauges add some weight. The savings and increases nearly cancel each other out with the car coming up a bit lighter than factory.

The GTO usually ran with empty trunk and low fuel levels for maximum acceleration, except for the times it was taken on road trips. The GTO rarely had cargo and carried passengers about a quarter of the mileage logged. Factoring the infrequent passenger loads, the car pulled about 400 pounds on average minus the savings of 100 pounds gas, placing the GTO 300 pounds above an approximate curb weight of 3,500 lbs for an average in use weight of 3,800 pounds.

The engine revved high because of the axle ratio. Below is a list of RPM speeds given by the aftermarket tachometer.

40 MPH=  2,500 RPM
50 MPH=  2,850 RPM
60 MPH=  3,300 RPM
70 MPH=  3,900 RPM
80 MPH=  4,200 RPM
90 MPH=  4,550 RPM
100 MPH= 4,850 RPM
110 MPH= 5,250 RPM
120 MPH= 5,800 RPM
130 MPH= 6,150 RPM

High octane leaded fuel was necessary to handle the extreme compression ratio and high RPM operating conditions. The GTO was driven year round hard and fast. The car enjoyed about 4 months of warm weather and suffered the remainder of the time outside during frigid cold weather and snow. When possible the block heater was used to aid warm-up times. The GTO was driven primarily on secondary country roads at high speeds on trips over 10 miles duration, returning 13 to 15 MPG. This is pretty impressive if the figures are correctly calculated. The logs are an approximation at best.

Below is a picture of the now brutalized body the winter prior to the car getting sold. If you look closely you can see that the Endura bumper is completely separated from the passenger front fender with a 1 inch gap.

69 gto mongrel snow

When body rust, shot rings and a freshly damaged frame conspired to make it time to part out the car, a speed shop visit was made to strip the car. The speed shop didn't want to take a chance on the engine. It was too iffy for yet another rebuild. Back then OEM engine blocks weren't the big deal they are today. This one had lost its serial number in a rebuild anyways. The speed shop bought the aftermarket gauges, aluminum radiator, mags, headers, dual exhaust, intake and carburetor.

To remain roadworthy during the last few months of use the speed shop installed restrictive passenger car exhaust discarded from another customers' Chevelle conversion to headers. The shop installed a passenger car carburetor and intake. A heavy junked copper radiator was installed. An old set of bias ply wide oval tires mounted on junkyard GM steel wheels replaced the lightweight mags and Michelin radials. The car was driven in this state for another six months before being parted out. The loss of high performance parts lowered the efficiency as will be seen in the logs below.


Below are the gas logs for the first stretch of relatively short trip operation in summer. The daily work trip was primarily highway driving which improves MPG. Work site distances were 9.3 and 12.7 miles one way: far enough to ensure engine was up to operating temps. Mixed into this was the typical cruising and partying from place to place that most muscle car owners engage in. The car was driven gingerly until the oil temp came up: after that all hell broke loose. Full throttle burnouts, high speeds on highways and stoplight drag racing were daily occurrences in this car.

Gas octane varied, averaging about 94 Octane. Leaded gas was used whenever possible. Sunoco was used often due to their high octane selection. This car thrived on high octane gasoline as proved by a prior owner who left several receipts in the glove box for aviation fuel! By seeking the highest octane, the scourge of ethanol laced gasoline was avoided for the most part of the driving life of this car. Modern gasoline with 10% ethanol reduces the total energy potential in gasoline and consequently lowers MPG.

Gas quantity is rounded off to the nearest full gallon in the log. Extrapolation of known exact fills provides a pretty close idea of the real amounts. No odometer check was ever made on this car. Comparing old odometer readings from trip logs with MapQuest tallies closely, suggesting that someone took the trouble to switch in the correct speedometer adaptor gear when the 4.33 axle and 140 MPH speedometer were installed.

The list below provides the odometer reading, the number of gallons and the octane of gas if it was noted. The column under Fill-up indicates the rare full tank of gas. The final column is MPG.

Odometer Gallons Octane Fill?  MPG (uncorrected)
6,516        16.4    
6,725         1.6    
6,749         5.5       
6,924         8.2    
7,049         2.7   Leaded 94   
7,089         4.1   Leaded 94   
7,117         2.7    
7,183         2.7    
7,217         3.3    
7,250         8.2    Leaded 94   
7,354         2.7    
7,398         3.3    
7,485         5.5    
7,562         8.2    
7,660         2.7    Leaded 94   
7,721        13.8                   FULL     
7,924         4.4    
8,019         1.7    
8,048         2.7    
8,098         7.7    
8,220        13.8   Leaded 94   
8,439         5.5                      Empty      
8,511        15.4                     FULL/  15.3 MPG

A 120 mile highway road trip to a neighboring town taken with several passengers and 200 pounds cargo started at 8,511.9 miles. Hot weather and steady cruising speeds around 65 mph boost MPG figures. Aside from this 120 mile road trip the entries below reflect hard driving.

The figures below include the amount of gas used between two Empty readings on the gas gauge. The empty range shows a rough MPG of 14.9 to 19.9 for an average of the two of 17.4 MPG. The more reliable Fill to Fill readings from this section produce 15.2 MPG, just one point off the previous calculation of 15.3.

Odometer Gallons Octane  Fill?   MPG (uncorrected) 
8,700          1.1    
8,800          5.7    
8,919         11.4  Leaded 94     
9,025          8.5    
9,202          8.5    
9,290          1.5    
9,345          2.8       
9,404          8.5    
9,501          2.2    
9,575          5.7    
9,631          5.3    
9,730          5.2    
9,835          3.0    
9,869          3.9    
9,920          6.3      
10,023        6.3    
10,110        7.6    
10,237        5.5                   Empty  
10,319        5.5                   Empty/  14.9 MPG
10,374        0.8    
10,400        5.5    
10,472        2.7        
10,609        1.9    
10,649        2.2    
10,676       12.4                   Empty/  19.1 MPG
10,848        5.3    
10,915        2.2    
10,963        8.0    
11,057        5.8  Leaded 94   
11,137        5.8    
11,222        5.3    
11,258        5.3    
11,357        2.6    
11,407        4.2    
11,457        5.3    
11,547       10.6 Leaded 94   
11,667       10.6    
11,834        7.6    
11,898        3.5    
11,996        5.5    
12,045        2.0    
12,065        5.0    
12,135        4.5    
12,248       12.6    
12,381       10.1  Leaded 94   
12,549        7.6    
12,642       10.1    
12,762        3.0      Leaded 94   
12,836       10.7                   FULL 15.2 MPG

69 gto mongrel icicles

As attested in the shot of the now battered GTO sprouting icicles, the entries below chronicle 4,623 miles of hard fast driving in sub zero weather with snow. 340.6 gallons were needed to cover the distance, which means 13.5 MPG. Long driving distances keep the efficiency pretty high despite horrible weather.

Odometer Gallons Octane  Fill?   MPG (uncorrected) 
12,936       5.0   
12,941       5.0    
13,185       9.1    
13,189       2.2   Leaded 94   
13,333       2.5    
13,366      10.1    
13,442       7.6    
13,564       8.1    
13,609       7.6    
13,715       8.8   Leaded 94   
13,864      11.0  Leaded 94   
13,959       5.5    
14,071      14.4    
14,204      11.0  Leaded 94   
14,280      11.0    
14,527      10.0    
14,643      11.0    
14,788      11.0    
14,929      11.0    
15,074      11.0    
15,288      11.0    
15,398      11.0    
15,549       5.5    
15,616       4.4    
15,675       6.1    
15,708       9.6    
15,884      11.0  Leaded 94   
16,000       9.4    
16,155       2.7    
16,195       5.5    
16,315       8.3    
16,500      13.8    
16,590       5.0    
16,677      11.0    
16,880       2.7    
16,900       8.3    
17,014      11.0    
17,140       5.5    
17,326       5.4    
17,397       3.3    
17,459      17.2        FULL 13.5 MPG

Below are the gas fills from a 500 mile road trip starting at 17,648 miles. The trip took the GTO through several cities with temperature about 40 degrees F. There were several passengers and no cargo. Speed varied from congested 60 MPH freeway driving up to 100 MPH two lane blacktop runs. The first MPG figure reflects usual driving. The second MPG figure is a pure 60 MPH highway cruise figure: an astonishing 22.8 MPG. The high compression engine is very efficient despite the 4.33 axle. Of course, a switched in speedometer and axle leaves mileage accuracy open to question.

Odometer Gallons Octane Fill?   MPG (uncorrected)
17,649       13.2                FULL   14.3 MPG
17,832        7.9                  X  
18,028        8.7                 FULL   22.8 MPG

Below are some hot weather hard driving figures. The Empty to Empty reading used 97.2 gallons to maintain an empty tank over 1,488 miles which is 15.3 MPG. This seems to be a common figure for this car.

Odometer Gallons Octane  Fill?   MPG (uncorrected)
18,221       10.4   
18,400        5.8                  Empty 
18,455        5.9   
18,550        5.8   
18,654        5.8   
18,698       11.6   
18,907        4.2   
18,959       11.6      
19,171       10.7  Leaded 94  
19,356        2.4   
19,379        2.2   
19,402        5.8   
19,498       11.6   
19,667        4.2   
19,700        9.6   
19,888        4.8                    Empty  appx 15.3 MPG
19,938        2.9   
19,984        5.8   
20,049        5.3  Leaded 94

20,160        3.6 
20,206        5.8 
20,296        2.9 
20,300        2.9 
20,356        1.5 
20,396        5.8

Starting at 20,460 miles a 316 mile road trip running against the clock to a nearby city was accomplished in less than 3 hours. This includes lost time in stop and go gridlock on city streets in two busy downtown cores leaving and arriving. The GTO posted a 105 MPH average speed with all city driving included. The highway portion was done at an indicated 120 MPH. There is no notation confirming this in the log, but the 20,660 mileage was likely a fill-up.

The return trip was the total opposite: severe fog limited average speeds to as low as 20 MPH, with speeds no higher than 60 in semi clear areas. The return trip took an entire night, arriving home at dawn. The MPG hovers around 19 MPG overall, but we can't break down the proportion of gas used during the three hour Gonzo run.

Odometer Gallons Octane  Fill?   MPG (uncorrected)
20,460        11.6                ?
20,660        10.3                ? 
20,820          8.7                X 
21,086          2.9                X

Below are logs with an overall average of 16.5 MPG counting back to the last fill-up at 18,028 miles. The efficiency of the GTO seems to have improved a bit. The driving was done in warmer weather and longer trips with frequent 32 mile secondary highway round trips in this batch of driving which contributes to the higher MPG.

Odometer Gallons Octane  Fill?   MPG (uncorrected)
21,140       5.3    
21,180       3.6    
21,262       2.7    Leaded 94   
21,200       4.2    
21,279       2.9    
21,460       2.9                  Empty  
21,498       5.8    
21,615       1.8                  Empty  
21,637       3.0    
21,670       4.2    
21,819       3.7  Leaded 94   
21,916       3.0    
21,962       1.8    
21,995       3.6    
22,065       3.0    
22,116       1.8    
22,188       4.8    
22,208       0.4                  Empty  
22,222       3.6    
22,283       2.9    
22,328       3.0    
22,378      12.0    
22,383       3.0    
22,457       1.8  Leaded 94   
22,500       2.7    
22,550      12.0    
22,700       9.0    
22,866       9.0    
23,015       6.0    
23,093       5.3  Leaded 94   
23,100       3.7  Leaded 94   
23,242       6.0    
23,390       3.6    
23,450      13.2                Full  16.5 MPG

Below are logs from winter. Taking the last 'empty' reading from 22,208 above to the 'empty' reading at 25,747 below the GTO used 220 gallons to cover 3,539 miles which is exactly 16 MPG.

It took 39.3 gallons to span the 426 miles between 'empty' to 'empty' readings from 25,747 to 26,173 miles which means the car was only getting 10.8 MPG. Reasons for this drop in MPG can be traced to sale of the performance parts which were exchanged with passenger car items.

The car now weighed more and suffered with a lean non performance carburetor and restrictive manifolds muffling the formerly razor sharp response. The GTO was still fast but became difficult to start with the substituted carburetor. Starting and restarting wastes gas. Driving conditions were unchanged, but driving style was restrained due to the damaged frame and the confidence squelching old bias ply tires now on the car. Slower driving theoretically would improve MPG.

Mileage plummeted about 5 MPG; a 30% loss of efficiency. The lean burning passenger car 4 barrel carburetor and intake combined with slower driving should have improved MPG. Carburetor frugality was negated by the loss of headers, the Flowmasters and radial tires. The heavier steel wheels, old copper radiator, iron intake and exhaust manifolds also added weight.

Odometer Gallons Octane  Fill?   MPG (uncorrected)
23,780        1.7  
23,820        1.5  
23,870      11.7 Leaded 94 
24,010        2.4  
24,100        8.7  
24,210        7.0  
24,301        3.5  
24,360        3.6  
24,435        5.8  
24,547        5.8  
24,616      11.7  
24,755        8.7  
24,895        8.7  
24,990        5.8  
25,058        5.8  
25,300        8.7  
25,384        4.1  
25,458        3.5  
25,535        5.8  
25,600        4.6  
25,700        3.5             
25,747        2.9                Empty  
25,777        8.7  
25,880        5.8  
25,950        1.7  
25,977        5.8  
26,060        4.0  
26,130        4.6              
26,173        8.7                Empty 
26,300        5.8  
26,400        5.8  
26,600        2.9  
26,642        4.0  

The OOCC GTO used 1,364 gallons to travel from 6,365 miles when bought with a quarter tank of gas until it was sold with a quarter tank at 26,980 miles. Counting back from the last recorded fill at 26,642 to the first mileage figure gives 20,277 miles which is an overall average of 14.8 MPG. Very impressive figures for an old muscle car with a performance engine and steep axle ratio driven hard. How is this possible?

First, we have to acknowledge that it might not be possible. No formal odometer check was made on this car, so exact MPG could be lower (or higher). It does seem likely that the odometer was within the usual 5% up or down accuracy typical of domestic cars from this era based on a MapQuest comparison to noted distances in a trip log.

If we accept the figures, how to account for stupendous MPG for a car like this? The first factor was the use of the highest quality highest octane gasoline available whenever possible. Modern ethanol laced gasoline is much less efficient due to a lower energy content than the old high test gasoline. Driving habits also contributed to ideal MPG. Total avoidance of slow driving in traffic negates the major weak point of a muscle car with a radical cam. Major cams will waste gas which pours out the exhaust pipes unburned at low RPMs, but these cams are efficient once you get it on. The owner of the GTO got it on whenever he could! Aside from driving fast, his trips avoided short trip stop and go. His work routes on open highways completely bypassed rush hour congestion.

Some street racer habits have negligible negative effect on MPG despite what seem to be logical perceptions. Flooring it out of a traffic light surprisingly doesn't use too much more gas than simply pulling out of a light normally. In either scenario, the MPG potential drops to just about zero. Some EPA tests suggest that the variance between aggressive acceleration and mild acceleration equals a mere 5% difference in city driving situations.

Some speed demon activities actually optimize MPG to peak potential for the vehicle. A typical neglected suburban grocery getter car back in the late 1970s or early 1980s had higher potential efficiency than the GTO, but these cars were taken in for lackadaisical budget garage tune ups when owners got around to it. The Mongrel GTO on the other hand was at peak potential all the time. Spark plugs were cleaned and gapped or changed with the best available plugs at least twice a week. Oil was changed constantly. Muscle cars are always in optimal tune.

Even tire pressure was maintained fanatically, and at 35 PSI for less rolling resistance it exceeded usual inflations used in this era. The average suburbanite never checks his tire pressure unless he has an obvious flat. Back then there were no computer monitored pressure warning systems. Some racers have the fronts up to 40 PSI and the rears down in the 20s for good dig in, but the Mongrel GTO had a great suspension that got the power to the ground. The GTO thrived on 35 PSI all around which provided excellent handling as well as aiding MPG.

The street racer strips his car well below standard factory curb weight in the endless quest to aid acceleration. The GTO owner employed old racer tricks of keeping the car empty (nothing in the trunk or glove box) and running a quarter tank or less of fuel. The GTO was also stripped of insulation, options and even standard equipment (carpet, back seat etc). The factory curb weight of a suburban commuter car is inflated with many options, a glove box and trunk filled to the brim with junk and a gas tank that is topped up weekly.

The Mongrel GTO also benefits from headers, large diameter exhaust, low restriction mufflers and high voltage ignition. These items not only improve power, but aid fuel economy.

Ultimately, the driving conditions are likely the biggest factor in this car history. Almost all of the 'commuter' trips occurred on virtually deserted highways or secondary highways and lasted for significant distances which wrung out maximum MPG from the wild beast.



























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Last Updated ( Saturday, 20 March 2021 08:43 )