Home Travel Stories Gas Logs 1964 CHEVROLET Impala 327-4 bbl MPG= 19.9 Hwy/ 15 Overall
1964 CHEVROLET Impala 327-4 bbl MPG= 19.9 Hwy/ 15 Overall PDF Print E-mail
Written by Double Dragon
Monday, 29 October 2012 11:14

1964 CHEVROLET Impala 327-4 bbl MPG= 19.9 Hwy/ 15 Overall Av


Writing and photography copyright D. S. Brown

Metric= 5.4 L engine- 11.8 L/100km Hwy, 15.7 L/100km Overall







Ron Ciraulo, the owner of this 1964 Chevrolet Impala kept fairly close tabs on his performance. Part of the explanation for his great MPG is due to the light weight of the car coupled with scrupulous tune-ups. The good MPG recorded by the 1969 GTO Mongrel also in the GAS LOGS section supports the benefit derived from weekly or even daily tuning.

Ron was a Day Two guy. All of his cars have mags, dual exhausts and receive constant mechanical attention. To see a full story on Ron's Impala, look in the CAR STORIES section of this website under the ONE OWNER section.

Every summer Ron took his family on vacation from the California Bay Area 180 miles east to Yosemite National Park in the interior of California. The peak MPG recorded was 19.9 MPG running at a steady 60-65 MPH for the 360 mile round trip. The Impala was loaded with two adults and several kids and provisions. On another occasion Ron netted 19.7 MPG.

Ron's numbers are nearly as good as the highway mileage recorded by a 1967 Pontiac Beaumont profiled in these GAS LOGS. The Beaumont had one peak highway run of 21 MPG but was only able to manage duplicate runs in the high 19s which merely equal Ron's repeated figures. The Beaumont is mechanically identical to a Chevelle which is the next size down in the Chevrolet hierarchy. The Beaumont was also running a smaller 283 engine and yet here is the larger Impala with a bigger engine matching it. How can this be?

A test 1967 Impala 327 was able to match another 1967 Impala that was fitted with the smaller 283 in magazine tests of MPG. The 327 has more power and doesn't work as hard at highway speeds. Throw in luggage and kids and the extra weight found in any vacation trip and you need the reserve a 327 offers. Additionally, the 4 barrel carburetor on the 327 will run on the two small primary bores of the carburetor at a steady highway cruise while the 283's 2 barrel carburetor relies on only two throats which have to cover a wider range of conditions and hence are larger. So despite being a larger car with more frontal area and a bigger engine, the combination of factors results in the full size Chevy equaling the intermediate.

In general use, the Impala returned 15 MPG over 4,000 miles of driving. Ron's work commute had the advantage of covering the less restricted highways of 1960s California. There was also some open road mountain driving included in that period of driving. Another factor is the lack of ethanol content in the gasoline back in those days. Ethanol content in gasoline lowers the energy potential of the gasoline and hence cuts MPG.

The Impala still posted decent mileage years down the line. When the engine was rebuilt, Ron took advantage of many speed tricks which create increased efficiency. The stock log type exhaust manifolds were replaced with the free breathing 'ram's head' exhaust manifolds from a 327 Corvette engine. An open element air cleaner substitutes for the restrictive single snorkel stock unit. Most of these gains in mechanical efficiency compensate for the diminished energy content of modern ethanol laced gasoline and increased traffic density.

Last Updated ( Friday, 19 March 2021 22:57 )