lapi

:-)

But in reality, the manual method is exact miles you get per gallon. If you drive 500 miles from a full tank and you add 20 gallon to fill the tank again, you've got 25mpg. Isn't it?

zekeman

I think the jury is still out on this. Google "computer driven mpg accuracy" and you see a multitude of articles related to the pros/cons of car computers vs manual calculations. Some say the manufacturer loads the deck in favor of high mpg statistics to sell their cars; others swear by the manual calculations. Personally, I'm in the latter group. Really, it's no big deal and is just a curiosity thing for me.

NABS4

It certainly is. It doesn't get any more accurate than miles driven/gal used. The computer is always overly optimistic which means that it was programmed to be this way.

Lookout57

What the computer calculates and displays has nothing to do with the EPA figures. So why would they stack the deck and mislead with what the computer displays?

zekeman

Hell, I don't know; Google it and read several of the articles. If you believe the computer as gospel, then you can stick with the computer.

dhc8guru

I believe when it comes to derived and computer calculations, they will always show derived being lower.
When you derive the MPG, you are also calculating the fuel that has evaporated from the tank. Something that I highly doubt any manufacture would do because it isn't being burned by the engine. Also, depending on fuel temperature at time of delivery has a small impact on derived calculation. Topping off versus just stopping when the handle releases. Another small effect in MPG calculation.
Both or our current cars have Avg. MPG computers and both have wide variances compared to manual calculations anywhere from 2 to 0.2 mpg lower.

A4rooster

Sure, but regardless, the amount of fuel put in the tank for the miles driven is the MPG I'm interested in as it's truly what I would be getting in MPG.

dhc8guru

Well my method is to take an average of the derived average MPG. Since for the most part in driving route is consistent 4 to 5 tanks good enough for me.