back on the MPG thing

[LCAM-01XA]

I run 235/85-16s, your 245/75-16s are just a bit smaller than mine. Here's a comparison between our trucks (mine is the left set of numbers, yours is on the right):

Tire diameter---------31"-----30"
OD gear ratio--------0.71----0.76
RPMs @ 60mph------1900----2100

Both are based on 4.10 rear gears, and both seem to run 100 rpms lower than what we actually see, but difference is about right - 200 rpms. Calculations done with this:
http://www.bgsoflex.com/rpmmph.html

 

[david85]

I think I'll try one of my most gruelling MPG tests next time I have to make the 200 mile trip......I'll limit my speed to 60 MPH and lock out the overdrive.

That would put me really close to 2000 RPM and reduce engine loading significantly, but it won't be easy keeping my speed that low. The truck keeps trying to jump out into the fast lane.

I'm seriously considering some sort of mild water injection system long term after thinking more about it. I don't need anything to dump it in by the gallon, just a tiny whiff to take the edge off while driving. Maybe something that activates once boost pressure is above 1 PSI.