I get consistently around 20 mpg + or -, depending on road use and how much is city, all city is around 17 1/2 to 18 1/2 mpg, all hwy use I keep around 1900 rpms.

Maybe my math is screwed up but I usually run out about 1/2 tank before I fill up, I always fill till the pump clicks off then hit it again after a few seconds until it clicks off again, then divide gallons used into miles driven????? by hand, I do this every fill up.

Oh, and this is with 285's/ 16's on the truck and not taking into allowance of the bigger tires. Which when I checked with my garmin GPS, my speedometer was 2 1/2 to the slower side.

I fill up at the same Fina (about 100gal per week) commute about 100 miles a day. And the rest is business related. I have averaged these numbers over several thousand gallons. These are not overhead numbers. The number is usually 23.7 MPG. I've put 53,000 miles on my truck sicne 06/06.I''ve made at least 6 trips of 1500 plus miles.

If I had to choose, it would be a toss up between the turnip truck and bad memory. [laugh] [laugh] In the 60's and 70's if a rancher couldn't average 25 MPH between Kansas City and Denver in the family sedan either he couldn't calculate or needed a tuneup. A Buick with a big V8 would cruise at 75 MPH, 1500 RPM, and not breathe hard.

I agree. A couple of other factors that havn't come up much is that everyone seems to be relying on the accuracy of their odometers. My guess is that most are off by probably 5%. In my case my odometer is closer with the 285's then it is with the stock tires. In order to be accurate we would all have to be using corrected odometers. Another factor for those who are experiencing truely poor mileage with 2nd gen trucks is that the mileage goes south when the injection pumps start to fail. At least that has been the first symptom I have noticed in my case.

Oh it would happen , but it was rare , I went to auctions for 15 yrs. [ sometimes driving back 50-70 cars & trucks ] once and a while we would get back with an example of this , one I remember was a Dodge P/U , 3/4 , 4x4 , 318 eng. , it seems to me it was a late 70s or early 80s truck , we drove it about 180 miles home from the auction and got 22 MPGs , I almost regret not keeping that one , but one thing I learned about making money at auctions , was to never fall in love with anything you were biding on .

My paw's '93 or '94 Chibby 1/2 ton 2WD SC 5.7L auto, would get 23 mpg if you took it easy enough. But that truck was probably 4,000 lbs or so. Possibly a shade less. But we're talking 6,500 lbs. minimum with 3/4 ton trucks here. My truck is 7,130 with a full tank of fuel but otherwise friggin' empty. Where 20 mpg is a lot more impressive.

- JyRO

I had a 57 Chevy (in 1967) and never once figured my mileage. [laugh] Who cared at $5.00 a fill up.

A mid-70's Buick Electra 455 is doing well to average 15mpg - don't see how it could touch 20, even if you take into account today's mileage-reducing ethanol-blended unleaded?

My truck usually get around 16-17 MPG depending on how I have been driving but I did much better at lower elevation and I got 21 MPG cruising at 70-75 MPH. My best tank up here in the thinner air has been about 20 MPG.

I know a guy that drove from Amirillo to Denton (down hill and had a tail wind)with an 03 dully SO auto and got a hand calculated 29.7 MPG at 55 MPH. Call him well disiplined or crazy to be able to drive 55 mph.

annabelle - When I go on a 'haul,' I run 65 mph max. That takes a lot of patience. But you get used to it ... especially when I consider all the dynamics of what's going on with all the weight I'm hauling / towing. AND mostly, when I consider the cost of diesel and how much I'm blowing through those 6 cylinders.

Then I think about cars of 40 years ago, and even about how it must have been before cars. Then 65 mph seems plenty fast enough. But 55 mph, whew, that would be really tought to do, especially empty.

Yes, around town I set my CC at 1800 RPM (65) and just let people pass me by. Going from 85 MPH getting 18 MPG or going 65 and getting 23.7 MPG tends to keep your fot off the floorboard.

Man...this thread is still around?

I am very opinionated about a 2nd Gen 24V that gets 20+ MPG....reason why, I have NEVER SEEN ONE IN REAL LIFE! Only on the web. I can see a 12V get up to 20 (BUT don’t tell me your doing it with 370’s, 3 or 4GSK, Laser/EDM cut DV’s, and a 0 plate!) and i can see an ISBe (03+ truck) get into the low 20's just because the injection system is stupid efficient....but the VP trucks....i just have a hard time seeing it!

I talk to a lot of folks at my job all over the US. This is one reasons why i feel the way I do. I talked to a chap out in CA. He said that he installed a FASS on his 2001 Dodge and it Dropped the mileage. I said OK and asked how much? 8 MPG!! WOW! OK.....so i asked where he was to begin with......Get this.....28 MPG TOWING A TRALIER!!! AND our system brought him down to 20 MPG.....I seriously had to call him back to keep from laughing out loud.

I don’t get any better than 18 on a good day...that’s it.....

I would LOVE to borrow someone’s ISB truck for a week and run a tank though it that claims 20 MPG+. I will never believe anyone until i calculate the numbers first hand and see it. I don’t doubt you can do it…but I would bet that the truck would not be any fun doing 20 MPH in a 55 everywhere….i don’t know…..people have pets peeves……this is one of mine I guess…..haha…..Maybe im just jelous!!!! [laugh] [dummy] [laugh]

That's pretty good, Dan! [laugh]
I want a truck that gets 28mpg pulling a trailer... then I'd buy TWO FASS's!

"Hi-mileage" people seem to get offended at the incredulous responses, but in physics there's no free lunch... big heavy trucks with plenty of power can only sip #2 so well. [coffee]

... and if anyone doesn't believe that, try eating it with a fork ;)

Not even believe Tim ,Dan?