MPG Normalization
 

I'm trying to make an estimate of how I'm doing that's a little more accurate. I almost never drive in towns or cities, so the EPA combined rating is a little off. That part's pretty easy to account for (just keep track of the fraction I spend at highway speeds), but the big hills here aren't. Can anyone suggest a non-arbitrary way to adjust for hilly terrain? What sorts of hill impact does the EPA even assume in their estimates? Adjusting the EPA rating may make more sense than trying to shift mine as their assumed driving style is known, right? Thanks.

Unless its part of the revised EPA formula, I don't think hills are considered. I think the EPA testing is all done on a dyno now.

-Jay

Keep in mind that under some circumstances, hills can boost your fuel economy due to loading the engine properly then coasting down the other side burning no or little fuel...

Good point! I meant specifically for trips I do both ways on.

I would call it even and not worry about the hills. The EPA combined estimate ought to be fine; you're not making it a target, you're comparing to it.

Do the best you can, compare it to the EPA estimate, and enjoy.

As good as my inflated numbers feel...I'm trying to get a feel for how close to the point of diminishing returns I am. I can at least do the city/highway adjustment, so that's something. No point in making a adjustment for the hills if it's just going to be arbitrary, that's for sure.

Wait a minute, I've got that backwards! Hills would probably hurt the EPA estimates, since a normal driver doesn't coast in neutral or take other such actions.

On modern cars, hills probably wouldn't change EPA estimates that much. At least, modern cars with good DFCO behavior...

Really? Anybody ever get to test their cars on a track or other long flat surface? That's the only way I can think that we'd have any actual data.

Since it'd err on the side of being conservative, I feel better about neglecting it anyway.

Searching around I saw a new (to me) driving tip:

gradually build up some momentum before going up a hill