I do a lot of "around town" driving. I.E., 45-50 mph, several stoplights. I don't flog my car (regularly...), but I'm not a slowpoke either. I'm averaging 19mpg. I'm getting this reading from both my trip computer as well as manual calculation after filling up.

NOW, possibly related, just this week, I replaced the Michelin Pilots in 225/45R17 that came with the car with some Generals (german high performance tire) in 215/45R17. These Generals as 5lbs lighter each, as well as being a better size for the car. I know this combonation together will help fuel mileage. I haven't even put 50 miles on the car since the new tires, so I haven't been able to tell if there is a difference in mileage (which I know there will be). I can tell you this, the car has more gusto to it. I love this car even more now!

 

I get about 18 MPG in the city but then again i have a wagon. I don't know if thats normal for a wagon or not.

 

Well, 5 pounds of rotational weight is ALOT.

I believe the conversion is 10 pounds rotational weight is equal to 100 pounds dead weight roughly.
So you're technically 200 pounds lighter now.

 

In the racing world, we use 10# unsprung = 50# of sprung weight. Either way, you've saved a significant amount of rotational mass, but do remember you are dealing with a tire that is now .2" shorter in diameter, which will aftificially help your mpg. - AB

 

^Oh, is is just a x5 multiplier?

Either way, it's a significant amount as you stated.

 

Thanks for the input, guys! I figured that I was getting pretty close to what I should be. I also just changed the oil and went to Mobil-1 10w30 synthetic. That ought to help as well. Although, I won't be able to find out for a couple of weeks....going on vacation next week, and we are griving my wife's car. I would rather take the 850R, but her SUV has more room for all of our stupid junk and our daughter. The 850R would be a lot more fun to drive through the mountains. oh well...