I've made a few changes over the past year in an attempt to improve economy (highway):

1. lowered speed to 66 mph (from 68 - 69)
2. Increased front tire pressure to 60 psi (from 55)
3. Added Schaeffer's Diesel Treat to the fuel -- mainly due to Spicer's excellent work on fuel lubricity
4. dropped the oil level in the pan by 1/2 quart in an attempt to reduce windage

One year ago, the Chevy had ~14k miles on it; it now has ~24k miles.

One year ago, the Chevy made 22.37 mpg on a ~4,000 mile trip. Just a couple weeks ago, it made 22.95 mpg on a ~2,000 mile trip (getting 24.3 on a ~800 mile segment with a decent tailwind). Based on some very lax methods, I believe numbers 3 and 4 above contributed nothing to the mpg gain, the increased front tire pressures a 'little', and slowing down by 3 mph contributed 'most' of the increase.

Truck is still stone stock, except for Schaeffer's Supreme 7000 in the pan and Redline gear lube in the rear-end.

Bill

Nice report. Those numbers are similar to what my truck gets. In the warmer weather it will average 23mpg with some city and mostly 70 mph highway driving. I run 80 psi in the front and slightly less in the rears on 265s. The engine, trans, and rear get full synthetic. My truck also has a bed cover, its suposed to help, not sure if it does? Last winter I put in 5w30 Amsoil and the mpg was up by 2 the whole winter plus it started allot easier on those -20F mournings. I put 15w40 back in for the summer.

Those are some great numbers -- both hp/tq and mpg -- very impressive.

Do you find 80 psi in the fronts to wear and handle ok with light loads?

Yes, tonneau's are supposed to reduce aero drag and, therefore, improve mileage. Supposedly, wind tunnel testing has shown that a cover over only the back half of the bed is best for aero. Of course, such a thing would make no sense in the real world, unless one never used the bed, and mpg was one's -only- concern. But I also remember hearing/reading that a full length tonneau was significantly better than none.

Schaeffer's 7000 is a synthetic blend listed as a 15W-40, but it actually spec's out to around a 8w-40 (if memory serves). I run it year 'round and it's worth right about 1 mpg for the Ford in my sig. Don't know how much it's worth in the Chevy, to be honest, because I like the oil so well it's been in the Chevy since 3k miles.

Bill

Yeah, with 80 psi in the fronts it seems to handle better, but the ride might not be as good. With new tires I got little bit of cupping on the fronts but after rotating them to the rear then rotating them to the front again it went away.

I got 17 mpg last week. Only I had 800 lbs of gas in a transfer tank and pulling a 19' fishing boat loaded to the gunnals with food, beer, etc. I was very suprised.