Since I switched from 205/45/17 (Pirelli RF) to 215/45/17 I've been getting worst mpg... I've tried Falken FK452 and Toyo PX4 now. Usually I got 300-310 miles with the 205/45/17, but now I'm getting just 275-285 with the 215/45/17...(full tank) Same driving conditions, just tires changed.
Does anybody have had this issue?... How many PSI do you usually use on your tires?

 

Tires can definitely affect mileage. Wider tires = more surface area on the ground = more friction = lower mpg. But, variances in fill-ups, brands, weather, etc, also affect MPG. I keep my psi at the pressure stated on the door sticker.

 

I can't attest for the tire type, but for the PSI I Like it at 28ish fronts, and 30-32 rears. But this is set to my 'way' of driving. I like a little more front end grip.

 

You've increased road resistance with the 215/45-17 tires. Which tires?
Did you check alignment? If something is not set to specs it could be dragging one or more of your tires- like if the toe setting is off.

Try a slightly higher pressure like 37 psi, this usually increases mpg and watch that you are keeping the speed steady.

On the opposite, I often use stock 15" MINI wheels and continental 175/65-15 tires to get good mpg, up to 29 with a mid modded MCS.

 

Well, the new tires are bigger so they are not going to report the same distance traveleed as the old ones. By my numbers your old tires were 95% of what the new ones are, so your odometer should be reporting 95% of the distance travelled with the new tires over what it used to read with the old ones. Accodring to your 2 lowest numbers you are gettign 92% of the total from a tank, so it could be just the diameter alone which is causing a false reading or maybe the new tires being wider does take a littel real mileage away as well.

 

I would think that the slightly larger tire diameter (assuming that's the case - with different tire brands, who knows) would cancel out any higher rolling resistance from the slightly wider tread.

However, the theory of the odometer not registering as many miles sounds plausible. If the wheels needed to turn x-number of times per (actual) mile before, they may be turning fewer times per (actual) mile now with the larger tire diameter, so the odometer would read fewer miles.

 

Leel's theory sounds to me. Thanks!
Anyone who has used 215/45/17 tires can prove this theory?
Should I switched back to 205/45/17 tires? (Toyo Proxes 4)
Thanks for your help.

 

i WENT FROM 175/65/15 TO 205/55/15 AND LOST 2MPG. Wider tires= greater rolling resistance=more engine effort=more fuel consumption. I then replaced my OEM air filter with a Mini Mania foam panel filter and got my 2 mpg back. I don't think tire brands have much to do with mpg. I run my Yokohama's at 35psi

 

Do you guys think I should go back to 205/45/17 so?
I need to decide by today.
Thanks for your help!

 

I went from 205/45/17 Pirelli eufori RF to 215/45/17 Goodyear Eagle F1 GS-D3 non-RF tires over a year ago. I run 33-35 psi in my Goodyears & have seen no change in my MPG

 

No, don't change. Because your loss in gas mileage is partly due to the change in odometer reading, you won't really be getting that much gas mileage back. For example, if you put roller skate wheels on your car, it might show you are getting 50 mpg because of how quickly the odometer spins versus burning fuel. But in reality, we all know that's not the case. I'd suggest that if you compared what you had spent in a month on fuel in the past versus what you are spending now, it wouldn't be much different...

 

So the mileage given by the computer with the 215/45/17 isn't real? Am I actually getting more than it says so?

 

im running 215/40/17 Fuzion ZRi tires and my MPG never drops below 32.5...ive owned bumbles for almost 2 years and once i figured out what works and what doesnt with the car the MPG has stayed steady...in fact on my road trip from san diego to indiana i nailed 40 mpg!i usually get atleast 400 a tank

 

go to http://www.1010tires.com/TireSizeCalculator.asp and put in the #'s for the stock 205's and the 215's and you'll see the differences in tire diameter, # of tire revs/mile, speedometer difference, etc.

I've been running 215/45/17's ever since my runflats were spent.

Hope that helps!

 

215/40-17 is smaller (23.8") than stock
215/45-17 is taller (24.7") than stock tire diameter
205/45-17 is about 24.3" tall
There is some variation with different tires
23.8 is 97.94% of 24.3 (2% smaller)
24.7 is 1.64% larger than 24.3
Thats only about 6 miles difference for 300 mile trip.

Smaller tires will rotate more often for a given distance, show more miles traveled on the odometer, show higher speeds on the speedometer, and throw off your mpg to a slightly higher amount assuming everything else is the same. So error will be higher mpg because your odometer is reading high.

Opposite for taller tires. You get lower speedometer and odometer readings and slightly less mpg calculated whether by computer or manually done due to lower odometer reading.

Choose whatever tire size you want, don't be too worried about small differences. Just keep tire pressures up and drive smoothly.

For me-
215/45-17 very fun to drive - 25 mpg commonly
175/65-15 just plodding along- up to 29 mpg if I try really hard.
Everything else is the same.

 

Bingo! Very good complete post clarifying all this.

 

See post #15 for the details.

Choice of tire size is within "close" limits of stock sized tire where + or - 2% of stock sized tire diameter is what I was referring to.

 

Yes, Minihune clarified what I was trying to say. Your mileage appears low, but it is likely still the same and the odometer is off.

If you have a GPS you could drive 100 miles and fill up to compare true miles travelled and what the true milage is.

 

Thanks Minhune and The Copi! Great info.
For what I've been feeling on the car, the 215/45/17 is a much softer ride, definetly... The only issue is the false reading of the speed and some less power from 0 mph. Nothing serious, but I think I have decided to keep them and enjoy them!

Thanks for your help!
God bless you guys