2005 Corolla CE ... mileage drop?

[The111]

I have a 2005 Corolla CE, I was averaging 350-370 mpg. At around 35k miles, I replaced the cheap (and now bald) factory tires with Fuzion HRI's. Now I am averaging 300-320 mpg, for the SAME driving conditions.

So...

1) Something coincidentally caused the mileage drop at the same time as I replaced the tires.

OR

2) The tires themselves have something to do with it.

A friend suggested that newer tires, with better tread will cause more friction which will drop efficiency by a bit. While I certainly agree with this, I would not expect such a DRASTIC (>10%) change.

Any thoughts?

Thanks!

[adsaba1969]

Larger tires or same size?

Have you been getting 300-320 on a consistent basis or just one tank?

When was the last time you did maintenance (pcv valve, air filter, etc..)?

[The111]

Same size tire, mileage has been consistent since the change for 5k miles. I have 40k miles on the car, I will have to go double check about the air filter.

[The111]

Bump... anybody else?