I got a '08 Scion Xd back in March and I still haven't figured out the MPG. According to the owners manual there are two MPG readings: Instataneous and Average. I found out that average MPG resets everytime you fill her up at the pump so I'm guessing it's not suprising if the dash reads 9.0 MPG when I leave the gas station? Later, with more driving, the MPG corrects itself to around 25-30+ MPG.

However, I'm concerned about the instantaneous MPG. When I'm at full stop, there is no reading, just three dashes but when I accelerate, the MPG keeps going up. For example, 0, 14.5, 34.2, 70, all the way to 99.9 MPG. When I brake, the readings decline back to three dashes. How am I suppose to read it? Is this suppose to be normal? And which meter readings are the EPA deriving their data from? Thanks.

 

What I have found out is that when you are driving for a long distance without constant stopping, you should look at the average, it should be pretty accurate if I am turning about 3K RPMs I am usually getting about 31.6MPG, and then when you stop, it will show an average for a quick second. Atleast that is what my xD reads?

 

I always have mine on the average display as well since I want to see what I'm getting and remind myself to go slower. The other mpg display I barely look at lol.

 

Instantaneous is going through a lot of calculations that could drive someone insane, because its doing what it says, instantaneous. Its basically there to help you figure out if your burning too much gas at a constant speed (Stay at 30 for about 30 secs at the same rpm range and it'll give you a pretty good assumption). i.e. driving at 50 at 4000rpms is going to give you 28 mpg where as driving at 60 at 2500rpms can give you 30mpg. Theres no point in paying attention to it if ur stoping and going. It reads nothing at a stop because your not moving, hence ur getting 0 miles to the gallon. And basically, your average display is taking all these numbers from instantaneous and creating and crunching them down to a simplified average.

 

Zefoxe is correct in the instantaneous mode it shows three dashes because you’re not moving i.e. 0 miles per gallon. I usually keep in on instantaneous to remind me not to step on the gas so much. Try to relax and cruise as much as possible. As for the EPA they get there ratings from a constant speed which usually never happens in the real world unless your on a long trip with no traffic and no hills to go up and down.

 

when your coasting, it'll read 99.9...

The whole point of instantaneous mpg is to show you your "driving habits" so to speak. Try doing this on a BMW. It fun to see the needle bouncing around while playing with the gas pedal.

 

I prefer the instantaneous because it shows you what effect the load / pedal is having upon your fuel delivery. You can learn a thing or two about your fuels system / electronic management by getting used to this mode.

Why do you think they have always told you to "avoid jackrabbit starts"? What your the gage when you do - you are dumping fuel into the cylinders to get all that weight moving quickly. You'll also notice that when maintaining a constant speed (say on cruise control) your car will ask for less fuel to stay at speed on a slight downhill.

It's all common sense, but it gets really interesting if you are trying to maximize your fuel economy. Of course, if you are racing around everywhere you go, you will get dizzy trying to focus on the constantly changing numbers.

I'm getting better than published gas mileage by paying attention to how my driving style effects consumption. I still occasionally chirp the tires in second, but generally speaking, I am pretty mellow when driving.