Combination Meter Replaced, lower MPG

I'd say give it a few tanks of gas...if they cut off power, the system may take time to recalibrate. After that we need to know if real MPG has changed or just on-screen MPG.

What was the bill in case I have to too $$?

PS- 10w30 is a little too thick think you want 5W30

PPS- New tires almost always cuts your MPG as the tread is thicker, so your car thinks you are going less revolutions for the same actual distance. See TireRack.com discussion of observed MPG physics related to new tires.

 

wjtracy hit the big ones. The Combination Meter is not the likely cause of your mpg hit. Most likely causes are:

Tires: Different tires have different amounts of rolling resistance. If you switch from a tire with very low rolling resistance to one higher, this can cause a large mpg hit. Tires have higher resistance for the first few thousand miles as they break in. Also minor is they are slightly larger in diameter, so your car won't think you've traveled as far.

Computer Reset: It's hard to say exactly, but my Prius also takes a small mpg hit for about 50 miles whenever I have to disconnect the battery.

Oil: In the US, the recommended oil is 5W-30. Running 10W-30 could cost you a percent or two in fuel economy from the extra resistance of the engine working against the thicker oil.