Bad Mileage 4.8i Sport Wheels. PSI Problem?

[youry]

Originally Posted by bawareca

My results are not scientific, but I have seen people here report over 500 miles on a full tank. I was never able to get over 450 miles even with soft driving style. My mileage varies very little from city to hwy. Doing 80 on the hwy is where the roll resistance will have most impact so it makes sense.

I get 500+ miles per tank(highway), 2012 X35i 56k, still running the original/factory Bridgestone RFT dueler tires (factory 18" wheels)

[macmac80210]

Originally Posted by youry

I get 500+ miles per tank(highway), 2012 X35i 56k, still running the original/factory Bridgestone RFT dueler tires (factory 18" wheels)

Tire size probably makes a huge difference, and you're also running a '12 3.5 and I'm running a '07 4.8.

I am now sitting right around 9.5 MPG after 2 tankfuls and a solid mixed-city commute. I have brand new Bridgestone tires, so I don't think that should be the issue. I have been trying to milk the mileage, but it's just not coming. I think the real issue is increased lb/ft of torque required at startup from 0mph because of the larger wheels. I was coming from a pair of 17" with a winter Bridgestone setup, and it's just frightening to see a 5+ MPG decrease with these things.

Any ideas on who to talk to about shitty mileage? Dealer or some tire place?

[macmac80210]

Originally Posted by ard

wow. cannot understand how tires/wheels can have such a massive impact on MPG. BMW fights for 0.1mpg for CAFE standards...2-3mpg seems impossible.

Tire wear is driven (virtually) ENTIRELY by alignment....anyone concerned with tire life that does not know their TOE numbers is lost...

I cannot understand it either. I think that I'll probably deflate them today, and see how my mileage is on a fresh tank. Right now, I'm running 5PSI over what some are suggesting, so that could be the issue, but I always was under the impression that higher was better for mileage. Maybe that's just old nonsense

[Padgett114]

We went from 19's to 20's with offset on our 2010 35D and didn't really see much of a decrease in MPG, still get great mileage.

[iceman2002benz]

The rims you brought might also play a role. you said 214 style, this means HEAVY china made ones. they will affect your mpg.

[14thbmw]

Wheel and tire weight matter a bit, tire width matters a lot. Higher inflation helps reduce rolling resistance. Diameter shouldn't matter unless it is causing your speedometer/odometer to read low (deflating MPG).

Look at the rear tire size on the i8 - there is a hint in that for getting higher mileage.

[bawareca]

Originally Posted by 14thbmw

Wheel and tire weight matter a bit, tire width matters a lot.

Exactly. Especially with a performance/high performance tires. Style 214 are very heavy indeed and that would affect the city mileage a bit.

[macmac80210]

Originally Posted by bawareca

Exactly. Especially with a performance/high performance tires. Style 214 are very heavy indeed and that would affect the city mileage a bit.

Yeah, it must just be the weight of them. I bought OEM ones, not China made, but still, I think they're pretty heavy when trying to put them on and off, certainly heavier than my previous, so I'll chalk it up to that.

I guess problem solved?

[macmac80210]

Originally Posted by iceman2002benz

The rims you brought might also play a role. you said 214 style, this means HEAVY china made ones. they will affect your mpg.

Is there any way to tell OEM from China ones?

[bawareca]

I dont think there are china clones 214 and i am pretty sure the copies will be lighter than the original. They will be less safe, but not heavier.