While its not exactly economical, I think the best mileage your going to get is a lot slower, more like 50MPH. I know most places you cant safely go that slow. I did an informal experiment with my overhead computer, with 3.92 gears, the best mileage I flattened out at was at 45-50 mph. Get in overdrive with the TC locked up, but not much faster. The faster you go the more wind resistance becomes a factor. Hypothetically speaking, if I could go on a strait flat road at about 45, my rig could get 20+. Normal driving i get 15-16.

 

I can't comment on mpg too much as I am so far from stock it can't be related to most other trucks.

In my area of BC 100kph is about max, the roads I travel are more like 80-90 kph so this makes a huge difference in mpg as you posted.

I remember when the US was 55 mph just for this reason but that was very long ago and not to sure if that would go over down there in this day and age.

Just some info the coefficient drag for 1500 trucks is 0.44 and for the 2500 it's 0.45 this info is in the fsm you just have to find it lol.

 

New, my '98 5.2 5spd 4x4 with 3.55's on 265-75-16's got 19 hwy - 16 city...
16yrs and 164K+ later, 14mpg is as good as I get... it doesn't seem to matter if it's city or highway... even if I really get into it for a tank full, 12.5mpg is about as bad as I can do.

 

I've already changed the cap, rotor and coil, just need to get around to the plugs and wires, supposedly going to be warm tomorrow, so I may do that before I get a load of firewood.

Just trying to get used to the truck on the highway right now. I'm not expecting drastic improvements, but anything that can help.

Then next weekend, after the tach, new transmission fluid and gear oil.

 

?? I was referring to the 20 mpg claim.....and pretty sure annihilator was as well

Funny tho-I'd be happy with 14...

 

5.9L 265-75-16 tires 3.55 gears, cold air induction, magnaflow exahaust = 14.1 mpg at 70 mph. Best I have ever done with 99K on a 2001 1500.

Biggest ouch = 7.9 mpg pulling a 5000 pound trailer through the hills of southern Indiana.

 

Yeah, the gas mileage drops like a rock made of neutronium when you put a load on 'em.

Welcome to DF!

 

I now know my RPM's, installed the tach this morning. New to V8's, so I thought the idle would've been higher than 550RPM.

 

Nope, when fully warmed, its right around 600 in gear.

 

After taking a cruise and finding that at 110KM/h 65ish MP/h I'm dead on 2000RPM and getting home and letting it idle, it stayed at 500RPM. When I initially start up, it goes from 1500 and slowly goes down yto 550-600, then evens out.