Bhsj13

I recently switched from Nitto NT555 245/45/17's to Nitto Motivo 235/45/17's on stock 8 enkei's and my Mileage per tank has gone way up. on the NT555's i usually get around 210-230 miles and now i have been getting 280+ miles a tank. im assuming it was the tire sizing?

MinusPrevious

iTrader: (3)

Looks like the real diff is the 555 is a softer tire at a 300 treadwear & the Motivo is a very hard, high mileage tire at a 560 treadwear

Tire pressure & driving habit could be a factor as well.

heel2toe

iTrader: (41)

Id be surprised to see that much of a difference so I'd imagine driving style and/or the places you were driving on the last tank were maybe flatter or more highway cruising vs stop and go. However as said above your replacement tires are a significantly harder compound and slightly narrower which equates to less rolling resistance. Plus youve got tire pressures to take into account (also mentioned) and the smaller tires are probably lighter as well which will have a positive impact on MPGs.

Bhsj13

since i have changed to this tire, it has been consistent around 270-290 miles per tank. this is with WOT pulls once or twice a day. i bet if i pushed it, i would get 300 when the light comes on.

GTijoejoe

iTrader: (25)

Without like serious investigation it would be hard to pin point it however a few things come to mind.
1) road load from the tire it self
2) change in tire rolling diameter providing a false/unequal distance