Rpms and fuel mileage

Gonna need to know tire size to calculate it.

My truck turns 1300 rpm at 65 in high gear.
13 double over, 3:55 rears, 11R 24.5 rubber.

 

http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_062746.swf

What kind of 22.5?

11R22.5, 275/80R22.5 or 255/70R22.5? It makes a pretty big difference.

0.73 final ratio (most common on Eaton transmissions), 3.55 rears with 11R22.5 at 1400 RPM does 65.1 mph. This is, from what little I know, seems to be the most common setup out there.

275/80R22.5 only does 62.8 mph.
255/70R22.5 only does 57.6 mph.

 

Google road speed calculator. With lo pro 22.5 you'll be about 1425-1430

 

Or you can use something like this spreadsheet I did that shows the road speed for the top 6 gears of a 13 (or 18 ) from 1200 RPM thru 1600 RPM. Makes for comparing gears next to each other and putting in all kinds of combinations of tires, rear ratios, etc. Uses same formula as the online stuff, but is quicker and more versatile. All one has to do is set the tire revolutions per mile (from the tire maker charts), and the rear diff ratio. Can't seem to get the Excel sheet to load here. Send me a PM with your email and I will forward it to you.

 

I was thinking 1400. But more importantly is the fuel hourly burn. I don't know off hand what you will be burning at 1400. That determines your fuel mileage. It's close to zero when you on a 20% and god knows how high it will go when you are eastbound in western Kansas with a stiff wind pushing you. Ive had as much as 12 to 15 miles to gallon there for a while. And gone through 30 gallons in one hour fighting mountain grades.

 

I run 13spd 3.58's on lp22.5's (295/75/22.5) 65mph is 1425rpm. If you're running 11R22.5 65mph should be 1350rpm. I pull a van trailer and average 6.2mpg but that's with a pre emission Detroit series 60 500/1650 and a daycab average 78,000lb gross in the northeast mainly NY, PA, NJ with plenty of grades and rolling hills. MPG will depend more on your aerodynamics (I have none) and the terrain your running.