Could people post what they get in real gas mileage vs. what the computer says? On a mostly highway trip yesterday, computer said 39.7 mpg and real number was 38.2 mpg. So the computer was optimistic by 1.5 mpg.

 

Wow. That's pretty good mileage whichever way you look at it. Our 2010 gets only about 21-22 in town and about 30-31 on the highway.

 

I never trust the computer readout. I did have one moment where it was EXACTLY what I got. I couldn't believe it! I haven't been tracking it much but since this last fill up I am to see where I'm at now that I've put almost 10,000 miles on it and I'd say it's nice and broken in now

 

Trip computers are never that accurate. I've never seen one that was less than 1 - 1.5 mpg to the good. They are usually thinking optimistically and I wouldn't trust them.
The old ones worked primarily with the engine manifold vacuum, reading it to determine where the throttle was and working with a set of pre-determined parameters (mathematics.) The newer ones take readings from all the sensors, but still use some engineers idea of how to interpret the info. It's not real world, but an estimate at best.
For accuracy do it the old-fashioned way. It's as accurate as you can get.

 

I would think that they now use signals sent to the fuel injection - but still don't expect them to be accurate. Even using the numbers on the pump and tripometer, need to consider difference between pumps nozzle shut off settings and mileage errors.


But I don't think I will ever see the EPA 40 mpg rating of my car, unless it is down hill from the mountains. The 2014 sure does coast good.

 

Yes, I agree, Timmons, so all we can do is the best we can do. But I find if I use the same station, same pump and fill up at roughly the same time of day consistently, and assuming no funny business with off-sized tires, that my mileage is also consistent using the numbers/calculation method.
I was once running 215/50 instead of the factory 205/50 sized tires and had the conversion figured out so I could adjust for the size difference every time.