I heard sport suspension with bigger tires increase friction, down force (with aero package) therefore worsens gas mileage. Is this true?

Bigger tires would cause more rolling resistance and hence slightly worse mileage.

C.

The suspension has nothing to do with consumption!
Lowering your G should have little effect but.........
when you put those heavy 20" wheels and tires on
you'll never see 20 mpg again......maybe downhill

I have a G35 sedan with 18in. that come with Sport Suspension package. So far with 1100miles, I get about 22mpg max even with freeway driving.

Some guy form another forum said it takes about 10K miles to fully break-in the vehicle then you would see the optimal fuel consumption.

It takes quite some time for an engine to get fully broken in, and yes I've heard 10k plus too, but you should realize good mileage long b4 that.

C.

nope... i can almost squeeze 22mpg out of my 6mt sport

Rode from atlanta to new jersey last week and got 26mpg in my 06 6MT. I was like wow!!

On my third gas tank (91octane) @1.1Kmiles, I got 19.5 with about 35% freeway and 65% the rest stop and go.