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D13 · 03-18-2011, 06:22 AM

250/3ott/3.42's with LT235/75R15 - 16.5's, 12mpg driven normal, 15 driven old person style, 17mpg short shifted, rolled to stop, 45mph max. 8500 GVW 3/4 ton.

Ditch the rear gears for a 3.42. Or swap in an OD trans. 15-17mpg is very achievable but not with a 4+ total gear ratio.

As an example, 67 piscayne (impala) 4-door, 250 3ott 3.08 gears P235/75R15's, 21mpg. Car never went over 55mph. So the economy is available, just have to tune it for it. Max efficiency around 2000 RPM.

03-18-2011, 06:22 AM	#13
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: Better gas mileage 250/3ott/3.42's with LT235/75R15 - 16.5's, 12mpg driven normal, 15 driven old person style, 17mpg short shifted, rolled to stop, 45mph max. 8500 GVW 3/4 ton. Ditch the rear gears for a 3.42. Or swap in an OD trans. 15-17mpg is very achievable but not with a 4+ total gear ratio. As an example, 67 piscayne (impala) 4-door, 250 3ott 3.08 gears P235/75R15's, 21mpg. Car never went over 55mph. So the economy is available, just have to tune it for it. Max efficiency around 2000 RPM. __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors