ok so i been looking at a lot of cars latly and been watching where they sit at rpm wise in relation to speed and mine seems like its really low for some odd reason....i got 3.11 gears and stock tranny as far as i know my rpm and speed are these are with my equus tack. if its right that could explain my decent gas mileage

55mph=1550rpm
65mph=1800rpm
70mph=2000rpm
75mph=2100rpm
80mph=2250rpm
85mph=2400rpm
90mph=2500rpm

 

Wow yours are low!! I have 3:73s with 31s and at 70 I'm around 23-2500RPMs. I'll get an exact tomorrow. I average 15.5-16mpg right now.

 

My 98, (211K miles) runs 2000 RPM at 70 MPH (GPS) and consistently gets 21 to 22 MPG. Drop to 65 MPH and it increases to 24.8 MPG. 5 MPH drop in speed = almost 13% increase in MPG!

 

My '02 has 32 x 11.5" tires, 3:42 gears & in OD I get around 1800 RPM at 70mph (without a head wind). Yes the PCM has been corrected for the tires.
Wind, cargo, level road or not, all has an effect on my RPM's with the BL & SL & larger tires though.
With 31 x 10.5's I was getting 1700 RPM at 60mph but at that time I doubt the PO had the PCM corrected for the taller tires.
MPG's suck all the time with the lifts & SC etc - but it's fun getting there!
Sadly the gf lives 3.5hrs away at highway speeds & ... well lets just say she costs a bit to see lol. Sorry hunny, you're more than worth it!
(she reads BF from time to time)

And WOW Capt. I have to find that magical equation to find mileage like that... what's 5 miles per hour? In my case 17.5 mins... pfft for that mileage difference it's a no brainer!

 

When i had a tach,with 235/75/15 tires and as far as i know stock 3.42's i was turning 2400 rpm at 65ish.

 

At 70 75 ish I run about 2800 3000 on 31s with 3.42s

 

OK wtf is the matter with my tach? I get around 1800 maybe 1900 in OD at 70 mph. But that's also confirmed by the ELM.

 

sounds like the tuner and the supercharger ROTTI lol

 

Nah, what tuner? It was tuned on the dyno, on the fly & he callibrated the tach, speedo etc to the dyno's readings. He put mathematical equations in the pcm so it made adjustments just as it were stock.
The SC only adds more air & the fuel trims, volume, spark duration etc had to be adjusted over the RPM range to get a proper burn to potential.
Check out the WoflPerformance link in my sig. I doubt he'd make any mistakes, expecially with it being on the dyno 4 times I think. We're all human though, who knows.

 

3.42 gears with 32.2 inch tires im at 1800 rpm at 70 2000 at 75