in older models with speedo gear in transmission - gear change affects speedo. (along with tire size).
in later models with speed sensor in rear diff that reads the tone ring, the gear change has no effect, and only the tires affect the speedo.

to know for sure, do a speedo test along the highway. hold 60 mph exactly and measure time between the mile markers. 60 mph will travel 1 mile in exactly 60 seconds.

 

Thanks, I know I have the speed sensor in the rear diff, I remember putting it on the new carrier during gear and carrier swap. I will have to do the highway test then. Does it also affect odometer accuracy. Guess I could do highway test for that too.

 

LAst time I measured it was 14 but now a year later i think its more like 10-12

 

Wow.. I get about 20 in town and have seen 26 on the interstate.


Diesels Rule..! just sayin..

 

Cummins 18 interstate (empty), 15 town.
Gassers local farm stuff and off road 11.

Diesels do rule for towing and mileage, but there's just some itches they can't scratch.

 

13-15 MPG Mixed, 16 if I granny it. This is based off the GPS, not the odometer.

 

15.65 average on the last fill up.

that's with 35" tires, 4.10 gears, and driving at a 380-400rwhp level...

 

You are correct.. Diesel still costs more per gallon. Also a good running V8 with the right muffler beats a Diesel hands down.

 

8.7 average, but i get ~13 on long highway trips.

I had the pcm updated with tire size when I went to 35's so it's pretty accurate.

 

Usually average 15MPG on the trip from Independence to Fairfax, and usually get 15.3MPG from Fairfax to Independence....