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When I first got my sport hybrid last June, I was averaging 29mpg with Bridgestone run flats in the stock size. Since changing to bigger Pilot sports, I cant consistently get above 26.8. Could what I thought was slight increase in tire size have that much of an adverse effect on gas mileage? Anyone else have the same thing happen?
 

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Hummm. I just uploaded the stock map and have 85 miles on the tank so far. With very light driving and two trips up the long steep hill to my house 28.2 mpg indicated.
My 1400-2000 RPM power feels like I have a bit more. The rocket power at 250-4000 RPM is gone since I'm back to stock. But still very good.

I will leave it stock for this tank. I now remember why I hesitated to tune it after my mods. The FI exhaust made such good power and better MPG.

The only down side is it takes a LOT longer to program from tuned to stock and back to tuned, and my EcuTec Dashboard does not work.

Im very tempted to dyno it with the stock map to see what I have with my mods, then reprogram to "tuned" and redyno.
 

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When I first got my sport hybrid last June, I was averaging 29mpg with Bridgestone run flats in the stock size. Since changing to bigger Pilot sports, I cant consistently get above 26.8. Could what I thought was slight increase in tire size have that much of an adverse effect on gas mileage? Anyone else have the same thing happen?
Wider tires will increase the wind resistance. There may be a small difference in rolling resistance also but rolling resistance is only a small fraction of wind resistance at speed.

Rolling resistance increases with speed are linear. Wind resistance is exponential.
 

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When I first got my sport hybrid last June, I was averaging 29mpg with Bridgestone run flats in the stock size. Since changing to bigger Pilot sports, I cant consistently get above 26.8. Could what I thought was slight increase in tire size have that much of an adverse effect on gas mileage? Anyone else have the same thing happen?
What size Pilot Sport tires did you put on the car?
 

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