My '95 Tbird 4.6 has 92,080 miles this morning, still gets 29-31 mpg regularly on the highways I drive by SGII or Math .... I tend to use US Rt 11 more than Interstate 81 though. On Interstate at 70, she drops some to upper 20s.
My '92 Sport still get's 22-24 running around and more like 25 on Rt 11 style 55 mph drives.
Originally Posted by 1996Project-bird
calibrated for a 4.6. No doubt about it because it never ever leaves my car.
I have a SGII that Ibought in 2010 and use between 5
vehicles, each has a cord and a Velcro spot on top of steering column. They are a '08 Mustang GT, '95 T-bird 4.6, '07 F150 5.4, '01 Mercury GM, and '03 Subaru Forester.
I find that the AVG MPG
is usually within a MPG of what I come up with when I divide miles by gallons at fill up IF I drove non stop between fillups
so that SGII has not reset itself. Some times it's spot on. When it's not that close, it's always after a stretch where I did stop one or more times between long enough to let SGII reset itself. I don't mean run it to empty either, you can .... and I do .... often stop and fill up after maybe 200 ... or even just 100 miles ... like a "rest stop" for me, my wife, and the car.
The calibrating that one does at fill ups (as I recall, I fooled with it a few years ago, not since
) with a SGII is primarily aimed at "miles to empty" as I recall, where you are entering fuel tank size and gallons at fill up .... though it may fine tune for GPH reading through the OBDII port. It also gets a MPH reading, and how it comes up with MPG is SPEED divided by GPH for instant MPG reading. AVG MPG takes in account how long at any instant MPGs as you travel.
I bought the Mustang more recently than the others and I have never calibrated it to the Mustang, but in comparison between the OEM on board MPG readings, the SGII and the "Math" way .... the SGII is right in there with the other two, if I haven't let it reset since prior fill up.
All of those vehicles have OEM size rubber on them, except the Subaru which has 225/60-16 tires in place of stock 215/60-16 tires .... which according to Garmin .... actually made it's speedo more accurate than originally and the MM on I-81 put the odometer very very close now. Garmin and many checks with a SW agree, the others speedos are pretty close to spot on both speed and odo wise .... certainly good enough for me.