I recently made a 352 mile trip on relatively flat state highways and secondary roads in MI with some small hills. I filled up at the Meijer in Dewitt, then I went to Chesaning, then to Harbor Beach, back to Chesaning, then I filled up at the Meijer in Ionia. I was cruising at 1500-1600 rpm and I got 21.95 mpg using 16.04 gallons. When accelerating I never let the motor see over 1800 rpm because I had a cargo in the bed for 80% of the trip. There was a light to medium wind from the south but most of the trip was East/West. The North/South part of the trip was even both ways so the wind didn't help out any. I ran the front/rear air pressure at 55/45 on the stock 245 wheels/tires when I was running empty, which was 20% of the trip. For 46% of the trip I had about 300# in the bed and two passengers with the air pressure still at 55/45 psi. For 34% of the trip I had 600# in the bed and 2 passengers so I upped the air pressure at 55/65 psi. The truck is still stock other than a PPE tow tune, blocked EGR and PCV reroute. I still have the stock intake, exhaust, ect.

Excellent numbers. I too find when you keep your foot out of it the low 20's are reached easily. Unfortunately this only accounts for about 2% of my driving. :D My highway avg. when not towing usually runs about 20 @ 70-75.

gotta love the stock tires ive gotten as good as 20.2 on the highway with the stock tires and with my 305's i get 16.5 on the highway

Does that include the 2mph faster than you are actually going with the stock tires....lol..j/k. What method did you use for the PCV reroute? where did you route to? I am noticing oil in my clear plastic boost line.

excellent

Awesome mileage. My last tank was 21.5 mpg hand calculated with the Power Pup on Performance, 4" dual exhaust with no cat, and 245's. I'll be putting my truck back to the stock programming for winter pretty soon, so goodbye mileage, until spring atleast.

That's some amazing milage right there... i've been seeing around 21mpg aswell when i take it easy...

THAT SETTLES IT!!! I've been on chevy forum for a long time... i'm starting a new club... 20+ MPG Club I am officially claiming spot 1 :D

There we go :D

I have stock tires... stock everything actually :(
Only have work equiptment.

woo whoo im gettin 15mpg.

woo whoo im gettin 15mpg.

X2

Ill grab 17-18 sometimes..

when I worked in lansing and I made the 60 miles one way trip, with the 85 prog in and my pizza cuttters @ 70PSI I always got 22-23-5 @ 65 MPH (HAND CALC) I accell like a granny, ran acetone also , I also had a topper on, now I work in waterford and with the traffic going to detroit I get 21

I have found that tire heigth is not as much as a factor (within reason) as tire width. I've run 245, 265, 285, 295, and 305 16's, getting lesser mpg with progressive tire width. Went to 245 X 19.5, and get between 19.5 and 20.5 mpg steadily at 65 mph on cruise. Hand calc fuel usuage, but regular uncorrected speedo mph, thus mpg should be even higher. Narrower tires have less wind drag, and roll a lot better. The neutral roll factor with the 19.5s is a whole lot better than 285's. With 19.5's, speedo shows 63 mph at 1500 rpm. Torque is not a factor - easily tow 22,000 gvcw on I-5 (level highway) getting hand calc 11.5 to 12.5 mpg at speedo 60 mph.