You beat me to it... only I thought it really goes down at over 65mph...

 

You need to drive like a Grandpa in that nice big truck... I rarely let my rpm's get over 2K. Just cruise along, I know it is hard with all that motor and exhaust, SLOW and steady wins the race!

Don't you know the story about the tortoise and the hair?!?!?

 

Is that the one where the tortoise was puking all over the place because he got a "hair" in his mouth and thought it might be someones lice covered pube?

 

Gross! Lmao

 

it does.

mpg is the best it can get at 55-60. this is with OD on, rpm modest at 1500-1700.

then a tiny bit less at 65

and finally - with that big *** front end pushing air, mpg's really drop at 75. mpg is not a smooth linear line. its a big old fat curve.

 

i have the same tires, and size... goodyear wrangler duratracs 285/75/16 load range E. however i have a 2--2.5" lift because of front diesel coil springs(to handle my 8' plow) and a 2" HD aal out back. im averaging 10-11 mpg. but i also dont have over drive, and im constantly doing 40+ on a regular basis. if i had overdrive, and 4.10's(next years tax returns) i would be getting 13-14, or higher mpg. another thing to use is something called star bright startron. on your first tank you will lose some mpg's but after that you should have between 2-3 mpg's. i havent had an usable results, as ive been driving around with my plow on recently, and currently am right now due to the storm.... but follow what everyone else is saying and you should be good!

 

Yeah, according to my "instant economy" readout on my truck, after 65MPH, it really goes down.

However, it goes WAY down if you try to hold 65MPH while going up a hill on the HWY. You have to switch OD OFF and your gas mileage will actually go UP when tackling hills on the HWY and trying to hold it at 55-60 MPH.

If you are cruising along at 80 MPH, my instant economy was about 10MPG, and sometimes less.

Out trucks like 35-40 MPH and 50-65 for gas mileage. Anything in between that or over 65 takes it down.

EDIT, I am talking about 4.10 gears. Gearing is a big part of it.

 

I did a full blown tune up awhile back, plenum, pcv valve, timing chain, plugs & wires, cap & rotor.

Then put some Wrangler Authority's on, 265/70/17E.

Took the truck to Atlanta Thursday night, ran around 70-75mph the trip, saw 15.4mpg, and that's with using the StarTron. My mpg's will drop if I don't use it....

 

I can go 2 weeks without refueling the 6.1L Challenger usually have 1\4 to 1\8 tank left. It has a slightly under 20 gallon tank.

My truck was a long bed with the 35 gallon tank. By the end of 2 weeks, it was on fumes. Literally, i would have the little yellow fuel pump light blaring at me the whole last day.

Kind of weird that I increased my displacement by 52 cubes, my HP by 195, TQ by 180 ft/lbs and ended up about 4-5mpgs better.


Bottom line, get a car, any car and it'll probably be better.

 

About a year ago when the conversation of speed versus mileage came up I was firmly of the mind that keep it at 65 mph or under and it's all about the same-it just depended on how fast you sped up to get to 65 and that was true to get 15-16 mpg for me. But since I have semi-retired last year and been building my house I have plenty of free time and a 27 mile drive over the mountain to our property several times a week. I am now getting 19-20 mpg out of my truck consistently. I have a 318, 46RE and 3.23 r/a. The biggest thing is I rarely drive over 55 mph and mostly keep it between 45-50 mph. When we had this fuel economy discussion last year I saw a video by a GM engineer who oversaw CAFE testing for their pickups. He said that for CAFE they assume most miles in a pickup will be suburban, so they use 45 mph as the benchmark and tune them to get the best efficiency with torque/hp at 45 mph. The video also had a graph showing speed/torque/mpg and they all three met at 45 mpg. He said all American manufacturers set their trucks computers and trans/diffs to maximize all 3 at 45 mph for the CAFE test. What I know is I have not got lower than 18 mpg(by fill ups not any gauge) since keeping it between 45-50.