1970 PONTIAC GTO Ram Air III 400-4 bbl- MPG= 15.8 Overall Print
Written by Double Dragon
Sunday, 31 July 2016 16:09

1970 PONTIAC GTO Ram Air III 400-4 bbl- MPG= 15.8 Overall


Writing and photography copyright D. S. Brown. Gas logs provided courtesy and copyright Bill.

Metric= 6.6 L engine-  L/100 km City and  L/100km Hwy


In this article we profile a 1970 Pontiac GTO owned by Bill. See the full story of his car under ONE FAMILY in the CAR STORIES section of this website.



In 1970 Ford had finally fixed their street image with monster big block engines while Chryslers were past masters of tearing apart competition with the 440 6 barrel carb street killer and the 426 Hemi.

General Motors finally responded in 1970 by lifting their 400 cubic inch limit on intermediate muscle cars. Pontiac regarded the 455 as a big station wagon engine for guys who wanted to load down a GTO with A/C and power accessories and retain strong off the line torque. Oldsmobile, Buick and Chevy went full tilt to build their 454 and 455 engines into screaming monsters.

Pontiac kept their focus on the 400 as the performance engine in 1970. The magazines that actually tested the 400 during this tsunami of 440 to 455 performance engines found them to be fast cars but a 400 was now considered 'small' in the 1970 pinnacle musclecar era.

CAR & DRIVER Jan, 1970 revisited the supercar that started the whole musclecar era. Back then musclecars were mainly referred to as 'supercars'.  C & D commented that the GTO had gained weight and was falling behind the manic musclecar times of giant big block cars. They cut a 15.0 second flat quarter mile time running a 455 and 4 speed.

CAR LIFE April, 1970 discovered that the 400 was still the fastest Pontiac. CL ran a 400 Ram Air III GTO with 4 speed and 3.90:1 axle against a 455 GTO with automatic and 3.55 axle and turned 14.6 and 14.7 in the quarter. These cars were pretty close.

HOT CARS May, 1970 ran the GTO with 455 engine and also commented that the GTO was not set up properly like it's GM big block cousins which had massive valves and heavy cams. HC came up with 13.98 in the quarter which is a much better time than CAR & DRIVER or CAR LIFE but these testers were drag strip nuts who knew how to wring out ever last molecule of potential from a car. C & D and CL gave you the off the showroom floor reality in their tests.

ROAD & TRACK April, 1970 tested a 400 Ram Air III GTO Judge 4 speed with 3.55 Positraction and covered the quarter mile in a respectable 14.77 seconds which is close to the time CL managed with a RA III.

MOTOR TREND June, 1970 tested the top dog GTO 400 Ram Air IV with close ratio 4 speed, 3.90 Posi and with 600 break in miles. In showroom condition it ran 14.67 in the quarter. Tinkering with plugs, shocks, distributor, and jetting but leaving stock tires and exhaust brought times down to 13.87. MT reported average MPG in the 10-12 range and a weight of 3,914 pounds when loaded with a half tank of gas. The GTO had power steering and brakes.

POPULAR HOT RODDING beat on a 1970 GTO Ram Air IV for their June, 1970 issue and despite being held back by a mere 3.23 axle the RA IV turned 14.5 in the quarter mile.

The Ram Air 400 Pontiac engines were still great performers but becoming overshadowed by high performance big blocks. In 1971 Pontiac put some performance parts onto a 455 and named it 455 H.O. These so called 'round port' engines have achieved lasting fame despite lowered compression ratios.




William's overall average MPG calculations came to 15.8 MPG. When checking his calculations in the gas log there are slight discrepancies between the exact MPG and his figures which were sometimes rounded off. Bill's original MPG figures are quoted with a slash followed by the precise calculation beside it for those readers who want absolute accuracy.

Currently the GTO runs on a mix of 60% leaded 110 octane and 40% unleaded 91 octane gasoline. Back in the day of course the car was run on high octane pump gas that was still readily available.

As seen below the first entry for the gas log runs from 93 miles to 221. Most cars were delivered with about 2 or 3 gallons of gas in the tank. Rather than try to extrapolate mileage from brand new, the original owner Bill's logs begin after 221 miles. The assumption is that he filled his tank at 93 miles and then again at 221 in order to calculate his MPG although this is not stated in the log.

Bill's GTO was still in break in mode during these early MPG figures. Cars back in the 1960s and 1970s were described as having 'tight' engines in most road tests usually until a little over 1,000 miles had elapsed. Until the engines fully break in performance in terms of acceleration and MPG will not yet be optimal.

Bill's GTO has a few options which add weight. The AMA spec sheet shows that the base curb weight of the 1970 Pontiac GTO hardtop is 3,781 pounds.

+ 110 pounds- A/C

+ 31 pounds- power steering

+ 28 pounds- TH400 automatic transmission

+ 26 pounds- Ram Air III 400 engine

+ 21 pounds- power disc brakes

+ 8 pounds - radio

= 4,005 pounds Total weight.

Adding driver weight and the custom built metal rack for the tool kit plus the weight of the steel toolbox and tools probably adds about 200 pounds for an as driven weight of 4,205 pounds when used as a work commuter without family members in the car.

70 Pontiac GTO RA III bill gas log 1

Odometer  Gallons     Full Tank?   MPG (uncorrected/ exact total)

00,093      unknown   unknown     N.A.

00,221       17.2         Full Tank     7.4/ n.a.

00,337       18.4         Full Tank     8.7/ 6.3

00,494       14.0         Full Tank     8.0/ 11.2

00,684       23.1         Full Tank     8.2/ 8.2

00,839       19.3         Full Tank     8.0/

00,959       13.6         Full Tank     8.7

01,111       15.0         Full Tank    10.1

01,255       16.0         Full Tank     9.0

01,467       15.4        Full Tank     14.0

01,657       16.2        Full Tank     11.7

01,890       17.9        Full Tank     13.0

02,044       17.0        Full Tank      9.0

02,204       18.1        Full Tank      8.8

02,376       19.2        Full Tank      8.9

02,451        7.0         Full Tank     10.1

02,596       18.3        Full Tank      8.0

02,754       16.1        Full Tank      9.8

02,839       13.0        Full Tank      6.5

02,996       13.0        Full Tank     12.0

03,209       15.0        Full Tank     14.2

03,374       17.2        Full Tank      9.5

When Bill summarized his driving for this period he came up with an overall average of 9.7 MPG driven over 3,281 miles. He used 354.0 gallons.

70 Pontiac GTO Ram Air III bill gas log page 2

Odometer  Gallons     Full Tank?   MPG (uncorrected)

3,567        16.5         Full Tank     11.7

3,708        10.1         Full Tank     14.0

3,883        14.4         Full Tank     12.1

4,080        14.4         Full Tank     14.0

4,276        14.6         Full Tank     14.0

4,319         5.4          Full Tank      9.2

70 Pontiac GTO Ram Air III bill gas log page 3

Odometer  Gallons     Full Tank?   MPG (uncorrected)

Last Updated ( Saturday, 20 March 2021 08:44 )