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Instantaneous MPG Meter

New 7/10/06

 With gas at near $3/gal I think I may have noticed a general slow down with PU and SUV drivers trying to get one more MPG out of their gas pigs.

Unlike IL which is flat and 4 lane western PA roads are composed of tight  'n twisty 2 lane pave goat trails and there is never an opportunity to by  pass slow traffic on secondary roads.   These slow farts driving their 6000# palaces are beginning to bust my  chops.

Anyone else notice?


My dad swears up and down that his excursion gets better MPG at 80 than 65. Therefore he drives 80. 15 MPG is the norm for highway driving. As soon as they invent a tin-can hybrid that seats 8, pulls a 3 ton trailer and gets better than 14 mpg while doing so, he'll sell it. We pulled a 91 SHO from Bristol, TN to Louisville, KY and got 14.5 mpg as our trip average. UHaul says 45 mph... my a**.

Alan Ridge

John Hrisin (sp?) on TechSHO had a post about this:

I have one of these in the Buick due to the lack of gauges and a driver information center/display.


It reads the data in the factory ECU via the OBD II port/link. For MPG it reads the injector pulse width (volume) and either or both the ABS wheel sensors (distance) and VSS (speed) to calculate instantaneous, daily, trip and average MPG readings. There are correction factors you can adjust for both distance and fuel volume used. You do that at fill up time. You check the amount that the unit says your car should have consumed against the amount you actually pumped into the tank to refill it. After 3-4 fill ups, you can get it zeroed in about as close as possible. As you adjust the calculated fill-up quantity to match the quantity that was pumped into the tank, the screen shows the correction factor being adjusted. This Winter the correction factor was at +6.4% (most likely due to the highly oxygenated fuels and/or higher level of ethanol present in the mix). Now that we are back into the warmer weather and Summer gasoline formulations, I have had to dial the calculated volume back until it again matches what was pumped into the tank and the correction factor now reads at +1.2%.

I set the unit’s display to show engine RPM, instantaneous MPG, water temperature and then whatever else looks interesting that day, maybe - air inlet temp, spark advance, engine load or battery voltage. The unit is pretty neat and allows you to learn how to maximize you MPG rating by giving you instant feed back as you alter your driving habits. For instance in my car due to when the torque converter locks up in 4th (OD) gear, the car has a much higher MPG rating when doing a steady 42 MPH  vs. 35 MPH. “But officer, I was just trying to save gas...” I also get a better MPG rating on the highway with the cruise set in the 68-70 MPH range rather than with the cruise set in the 60-65 MPH range. No 100% sure why, but it could have something to do with engine RPM and VE, resonance tuning of the intake, time and distance factors, the rotation of the earth or the alignment of the moon and stars who knows. But that’s what I see on a consistent basis, same day/direction/route.

As always YMMV ;)

Paul L Fisher

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