Just drove from Alamogordo to Roswell NM. 32.2 MPG when I pulled into the garage. Was as high as 34.3 on the highway. Not bad for a 400 horse engine.

 

Is that from the inboard computer or hand calculated

 

Thats really good. My 3.7 doesnt even do that good.

Matthew

 

I've done several tests of our 2008's readout versus math (and versus Scan Gage II though the SGII resets itself if you stop between tanks so that throws it off unless you run without shutting off between fuel stops) .... and the car's factory supplied readout is within a tenth of a MPG of what math yields over all tank to tank, same station, same pump (Greenville, Va. BP, pump #7).

Below is from our 2008 GT man. in the Shenandoah Valley of Virginia, US Rt 11 and just "driving" without doing anything special .... there are many hills and some stop lights and such. We just bought it June 19th this year and needless to say .... are pleasantly surprised.

 

^^^This.

Although there are a few of the 05 thru 10 onboards that are pretty accurate, the vast majority are off by 1-2 MPG (high). There was a lot of input on this from the forum members over the past few years. Unless you hand calculate, at least for the first 50-100 fill-ups, AND reset the onboard at each fill-up you haven't a clue what your actual fuel mileage is.

My '07 GT is off by 1.5-2 MPG.
My '08 Toyota SUV is off by 2-2.5 MPG.
My wife's '06 V6 Pony is off by about 0.2 MPG

As long as you're cruising in the sweet spot (which is often around 1500-1800 RPM), fuel mileage can be awesome.

 

Hand calculation is still just an estimate you realize? You are assuming that when you fill up nothing has changed and that you are putting exactly the amount of gas in your car as you burned since the last fill up. But differences in pressure at the pump, temperature, the vapor in your gas tank, sensor on the pump to shut off, will all affect how much you are putting back in.

 

with standerd 17 inch wheels and good tyre pressure i once got 30mpg.
that was cruising at 55 mph.
i get max 25 mpg with 20 inch rims.

 

What's MPG? I think I heard my in-laws mention that when they were talking about their Matrix and Prius. I don't think any of my cars have come with the MPG option.

 

True, but when you AVERAGE those calculations, the majority WILL get a more accurate value than the onboard provides. No sense believing that you're averaging 28 MPG when the reality is 26.

 

That's why I use the same pump at the same station .... that and it's just convenient to me .... and a habit .... after all these years I know how to accurately compute MPG. I like how the Mustang doesn't reset itself when shut off but maintains it's readings until the driver resets it at next fill .... miles, gallons used, MPG, all reset.

Interestingly, while the odometer appears to be very very close, the speedometer reads almost 2 mph fast at 60. Guess that's maybe designed in to help keep the license clear for a more "pleasant driving experience"? I like fun driving, the knowledge that it'll go when I want to go, the sounds, good handling .... but I like saving some $$$ too (and I intend that October 1977 ticket, the latest of 9 which I received, to be my last ticket ever). Stretching those gallons over as many miles as I can is a game I play also. MPG is affected greatly by driver's habits. A soft gas pedal application combined with anticipation of hills, stops, and a large dose of patience will go along ways in saving $ at the pump.