So got new Sumitumo tires, same size as stock and I'm gettin 3 less MPGs. Whats up with that?

 

there are virtually 100 variables.

 

Hand calculated or lie-o-meter.

And yes there are many variables. Unless you got a set of mudders, I don't see how simply a different tire MFG would bang you that much for worse mileage. Just my opinion.

 

probably the winter-mixed fuel that gas stations have converted over to this time of the year.

 

I had the same experience when I changed tires. There are many variables to consider, but putting on a tire that has a higher rolling resistance can without a doubt change your MPG by quite a bit.

 

some tires can do this depending on what tires you were running before, the temperatures, etc.

To keep it short and simple, running a summer tire in cold = Poor MPG and performance. Running a crappy All Season tire on High Performance car = Poor MPG.

 

I switched from winter tires to performance all season Sumitumos. I used the MPG monitor on the car. Haven' even changed my driving at all.