Poor fuel mileage - Impala Tech
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post #1 of 7 (permalink) Old 08-27-2019, 10:22 PM Thread Starter
 
 
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Poor fuel mileage

I have an original 64 impala base model with a stock 327 all original. Rochester 4GC carb.
I’m getting 9-10 mpg. I’ve been told that’s about the best I’ll get because it’s just old. It runs, drives, and starts cold just fine. No smoke. Idles nicely. Seems normal and smooth. Drives nice and normal as well. Doesn’t have any punch but it’s just stock. Should I be getting better mpg? What can cause low fuel mileage? And were should I start?
Thanks for any advice.
DN
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post #2 of 7 (permalink) Old 08-28-2019, 06:10 AM
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What transmission and rear axle ratio?

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post #3 of 7 (permalink) Old 08-28-2019, 08:48 AM
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Quote:
Originally Posted by ImpalasDave View Post
I have an original 64 impala base model with a stock 327 all original. Rochester 4GC carb.
I’m getting 9-10 mpg. I’ve been told that’s about the best I’ll get because it’s just old. It runs, drives, and starts cold just fine. No smoke. Idles nicely. Seems normal and smooth. Drives nice and normal as well. Doesn’t have any punch but it’s just stock. Should I be getting better mpg? What can cause low fuel mileage? And were should I start?
Thanks for any advice.
DN


Not because it's 'old'. With today's gas, that sounds about right for 'around town'. 'Highway' 14 or so. A 10% ethanol mixture reduces mileage by about 15% (my experience).

My '63 Impala 283 2 bbl (in 1968) used to average about 16 but that was almost 90% 'highway' and gas w/o ethanol. It was a 3 speed manual w/3.36 rear.

Gear ratio and driving 'style' impact mileage too.
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post #4 of 7 (permalink) Old 08-28-2019, 11:39 AM
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Need transmission and rear ratio. The new fuel does make a difference and a good tune up will also. Going from points to MSD ignition should also help fuel mileage. If your running a power glide it is probably one of the least fuel efficient transmissions in these cars and if it even has a minor slip it will affect fuel mileage. Granted I have yet to see a stock power glide that doesn't have a minor slip. If it is a stick shift it could be more about where you are shifting to get whatever giddy-up you can get out of it. 327 likes to produce power at higher RPM where your engine uses more go go juice.
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post #5 of 7 (permalink) Old 08-28-2019, 04:13 PM
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Welcome to the Team!

Mileage depends upon gearing, motor size and air fuel mixture as well as ignition timing.
I think you would be better served with a Rochester QuadraJet (has tiny primaries) more ignition advance if your gas can with stand it without knocking and a tranny change.

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post #6 of 7 (permalink) Old 08-29-2019, 06:33 PM
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On my 64, I get about the same MPG on my 327 that has been bored and stroked to 383 (granted it has a 700r4 transmission which should help). So that seems like you should be able to do better.

1964 Impala 4 door sedan

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post #7 of 7 (permalink) Old 08-30-2019, 10:33 AM
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I have to admit that as a current owner of few classic cars, and previous owner of many, I have never ever bothered to calculate fuel mileage.
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