BJ8 Mileage Expectations

Hello, all.

We are 200 miles into the break-in phase of our just recently restored '67 BJ8. The engine was completely rebuilt, but no performance upgrades, just some metallurgy updates and a slight re-bore with new pistons, valves, bearings, etc. I last drove the car in 1978 as a young twenty-something and I'm pretty sure I paid no attention whatsoever to the mileage the car was getting at the time. When it needed gas, I put some in (when I could afford it).

Over the last two weeks we did a fill / zero the trip odometer / drive / refill / calculate the mileage exercise. It came out at 20.3 mpg. We are using 93 octane with ethanol.

Since I never paid any attention way back when, I know I have no basis for this comment, but 20.3 strikes me as high.

Would any of you who keep track of mileage on a BJ8 be willing to share what you find to be typical mileage?

Thanks in advance.

Ken in NC

I've put many miles on my BJ8 on long road trips and have tracked the mileage pretty closely. Before and after an overhaul I saw/see:

- 15MPG around town in stop-and-go traffic
- 18-19 with 'hard' driving; i.e. 80MPH on freeways for hours--glad I have a Lempert rearend --or pulling a grade
- up to 24MPG with easy highway; i.e. 55-60MPH in OR
- 19-20MPG in 'overall' mileage; i.e. a mix of the above

I usually fuel with 91-octane/10% ethanol as that's the best we get here on the Left Coast. When I can get real gas, I don't see a calculable difference with booze gas.

There's not any "stop and go" driving where I live but otherwise my experience is about 1-2 mpg more than what Bob posts which I attribute to the lower weight of a 100.

16 mpg- to 20 just depends on how the foot hits the metal

Its SMILES per gallon.

Hi All,

Using 91 Octane pump fuel, 17 MPG give or take 2 MPG, is the best I have been able to do in years. In 1971 I did get extraordinary mileage when the rear carburetor needle got loose and would fall from piston vibration to close off fuel to the back 3 cylinders. Although highway driving in OD provided fuel usage well north of 30 MPG, with reasonable acceleration at highway speed, if the needle did not catch when the piston fell at idle, start-off would require riding the clutch to get moving.

Over the years, I often wonder if it would be of benefit to install an electric valve for shutting fuel to the rear carburetor when highway cruising. Concerned the rear cylinder valves would not receive sufficient led for lubrication, I never installed the electric valve and discarded the idea. I was intrigued when GM introduced their 8/6/4 engine that provided a similar reduction of cylinder usage economy.

Ray(64BJ8P1)

I have a BJ7 and when I first bought the car back in 2002 I was getting exceptional miles per gallon - great, but the car would not go above 75 MPH not so great - ?

I bit like Ray above but with a difference, I found that the fuel line between float chamber and jet was clogged by the little rubber seal at the float chamber end resulting in a very lean mixture indeed from one carb supplying 6 cylinders.

I guess we are around 13 around town and 22 on a run.



Bob

Thanks to all. Our driving in the test was mostly country roads (35-50 mph) and some in town with stop lights. I should have mentioned the car has the Smitty/Delaney 5-speed, so overdrive was not a factor. The 93 octane is Shell with 10-15% ethanol. I plan to use 90 octane ethanol-free when longer non-use periods are expected.

So, bottom line, it sounds like our 20 smiles per gallon was in the ballpark.

Thanks again, folks. This forum is a gold mine of knowledgeable and helpful enthusiasts.

Ken