Fuel economy sucks with my MS6 rims

[bho15]

Currently own a 2.3L Mazda 3 and have MS6 oem 18 rims with kumho SPT tires that weigh approx. 24lbs (225/40/18). I feel my gas mileage has decreased a lot.

If I get lighter tires would it help, or should I just scrap my 18s and go to 17s?

[Chester_Lampwick]

Dude really? "I feel my gas mileage has decreased a lot." Really?

How about recording the odometer and litres to fill over a couple weeks? It would be good if you've done this previously for a baseline too. Perception isn't really a good gauge of fuel economy.

[bho15]

When I had my 17 stock wheels, which was before the summer I would normally get between 500-550km on a full tank. Since the switch to 18s, I get about 420-450km, 500 if I'm lucky.

[bho15]

And it's mostly city driving.

[BMWWW]

There is a slight change in mileage due to weight, but don't forget to account for the change in weather as well.

Also, we're assuming that nothing else on the car has changed. (Tire pressures, and mechanical condition of everything else).

A change of 100km/tank seems excessive to me. Double check everything.

[cklwilliam]

There is a slight change in mileage due to weight, but don't forget to account for the change in weather as well.

Also, we're assuming that nothing else on the car has changed. (Tire pressures, and mechanical condition of everything else).

A change of 100km/tank seems excessive to me. Double check everything.

thats what happened to me couple weeks ago, i pretty much lost 80 - 120 km per tank. then i switched gas station and it gone back to normal so far o_O... so maybe its the gas that you're pumping?

[STeeLy]

Tire pressure is a big one.

When I had the RX-8 rims on my 3, at first I was running close to 7L/100km highway. I checked the tire pressure, it was at 30 and I put it up to 32 on all 4 corners. I ran about 6.5L/100km highway after that.

[The Wolf]

When I had my 17 stock wheels, which was before the summer I would normally get between 500-550km on a full tank. Since the switch to 18s, I get about 420-450km, 500 if I'm lucky.

hey man, I can do you a favour.
if you want great fuel mileage, I'll trade you my stock 16's straight up for the MS3's. With proper tire pressure and a steady foot you could push 650km/tank.

No need to thank me, It's just the kind of guy I am. I like to help people.

[pacmann33]

It will decrease a little, but not enough for you to notice. The cold weather has a very dramatic influence on your fuel mileage. I guarantee that is what you have noticed.

I got rid of my 18's because of the weight mainly, and a few other factors. Weight was what really bothered me. I had 2010 Speed3 18's. Overall I'm glad they're gone but I will miss the awesome look come springtime.

[rukus]

could you speedo/odometer be off due to the larger diameter, thus altering your mileage?

[gotak]

Are you sure the 18 inch rims are lighter?

http://www.caranddriver.com/features/10q1/effects_of_upsized_wheels_and_tires_tested-tech_dept

[G-daddy]

What mileage is everyone getting? I just calculated 8.9L/100km, and I got a 2.0L. WTF. Will check tire pressure tomorrow.

[gotak]

That's pretty bad since I get like 9.7 9.8 on the speed 3 and I am not a light foot.

[bman13]

hey man, I can do you a favour.
if you want great fuel mileage, I'll trade you my stock 16's straight up for the MS3's. With proper tire pressure and a steady foot you could push 650km/tank.

No need to thank me, It's just the kind of guy I am. I like to help people.

:chuckle

[Wix]

you should calculate your L/100km to compare, instead of using km's driven

my mileage is terrible for a '10 2.0L

[rajin929]

rotational mass is a bizzatch at times

[bho15]

Thanks for the offer. I might hold off trading them or selling them till next year. Checked tire pressure (33psi) and I calculated 10.1L/100km.

[Unoriginalusername]

The temperature has dropped significantly over the past few weeks... cars don't get as good MPG in the cold, are you sure you're not comparing apples and oranges? you could get away with a few more PSI cold as well.

Could also be time for a new air filter etc.

[BMWWW]

could you speedo/odometer be off due to the larger diameter, thus altering your mileage?

This will have a significant impact as well...

GPS has my 17's with a 45-ratio sidewall as almost 15km/h off at 120km/h. I would have to drive at an indicated 135'ish to be actually travelling at 120km/h. (Mazda 6).

[G-daddy]

That's pretty bad since I get like 9.7 9.8 on the speed 3 and I am not a light foot.

Yah, my car's bone stock too. I live uptown and drive downtown to work. Would that have something to do with it? Driving there in the morning is a breeze (relatively), but I am stuck crawling on the DVP for about 50 minutes on the commute home though.

[gotak]

Yah, my car's bone stock too. I live uptown and drive downtown to work. Would that have something to do with it? Driving there in the morning is a breeze (relatively), but I am stuck crawling on the DVP for about 50 minutes on the commute home though.

It's manual? That might be the case my rate goes up 1 to 2 liters doing DVP.

[G-daddy]

It's manual? That might be the case my rate goes up 1 to 2 liters doing DVP.

Yep, manual. I'll be switching to lighter wheels (albeit larger) in spring though. We'll see if that helps.

[kckev99]

If you're worried about weight get a set of these:
http://www.tirerack.com/wheels/results.jsp?filterSize=18&filterFinish=All&filterBrand=O.Z.&filterSpecial=false&filterNew=All&autoMake=Mazda&autoModel=Mazda3+4-Door&autoYear=2010&autoModClar=i+Sport&sort=Brand

O.Z. Alleggerita HLT - 16.4lbs

My brother had a set of Super Leggera on his Integra GS-R which were also about the same weight, it made the steering feel a bit light.