[Alex V.]

Originally Posted by BigRandy

Sounds encouraging. I'd be delighted to see 10. It's been getting 5 in the city and the best ever was 7.5 on the highway. It's got 373's but nobody I know of gets that kind of mileage

Most don't, so don't get your hopes up too high. But I've spent 55,000 mi. in this truck and have done the math too many times for it to be wrong. Yesterday I'd let it get so low the needle had stopped moving - I pumped $30 into it (didn't pay specific attention but @ no less than $2.55 a gallon) and drove 92 miles, half that in a heck of a hurry doing 70 MPH (3,200 RPM) and passing quite a bit, the other half at a steady 60-65 like I usually do, and when I pulled back in the needle was back below 1/4 but not closer to the 1/8 mark yet. So if I burned 9 of those 11-something gallons I pumped, I still got exactly 10 MPG. That's with syn blend 10w30 in the engine and Amsoil 75w110 in the rear end, and stock everything with the TH400, 4.10's, and 32" high 235/85r16 tires.

Not too long after I messed with the secondaries last year I towed a Jeep CJ7 to St. Louis and my first tank (doing 65 with the cruise set part of the way) was 7.3, and that's the worst I've ever seen the truck get by a decent margin which told me that I'd got the secondaries a little too loose. But anyway, all that is to say, a big block can drink a lot of gas and be perfectly happy, but it's possible to get 10 or a bit better in the right conditions.