Original Fuel Mileage?

[GaryS]

My family and I owned several slants from 1960 on, and I worked at a C-P dealer in sales in 1964, where I drove countless slant sixes, both automatic and manual, and in all body styles. I've always carried a log book and calculated mileage for the entire time I owned the car.

Real world combined driving when the slants were new was about 18-22, and the body style didn't make much difference. Hiway driving got about two miles more. The best slant I drove for mileage was my dad's '61 Savoy, 225 auto. I would get an honest, measured 26 on trips, and don't remember it ever getting lower than 18.

My '63 Valiant would get 25, and my current '64 convertible has a best of 21 and a combined average of 18. Worst slant I owned was a '75 Valiant that got between 15 and 17 combined, and it was a gutless wonder.

If 1960s real gas was more available today, you could expect 10% better. I owned the '75 during the time ethanol was only required in winter in my state, so mileage dropped 10% when the switch from summer gas was made, and increased the same amount when seasons switched again.

 

[doc540]

Might try to change jets in the 390 Holley and lean it out a bit.

Just for something to fiddle with.

 

[slantsixdan]

What fuel mileage did a STOCK 1961, 225 Slant Six, A904 A body get with a 3:23 axle ratio?

Realistically: 15ish to 20ish. There will always be those who claim to remember getting something like 25 mpg uphill at 80 mph rain or shine; usually these claims are due to faulty memory or odometers running way too fast.

See here (figures for 170 and 225 engine, auto and manual transmission all mixed together) and here (225/automatic, but equipped with a silly 3.91 rear axle) and here (again, a mix of 170 and 225 engines, auto and manual transmissions…look at there, the most common answer to the question "What's your gas mileage?" was "I donno").

 

[doc540]

Thanks!