# Sudden drop in fuel mileage. Big Time



## [email protected] (Feb 3, 2014)

I posted this in the Jetta VI section but figured I may get more answers here. Atleast thats my hope.
Last Monday I put my new wheels on which are 18X8.5. I filled up and as always, reset my odometer. From full to gas light, I got 283 miles. I didnt change my driving habits at all and I usually see 320+. Could this decrease be from the wheels? They are lighter than the stock 16s and I believe the overall diameter is similar. I just did my 40K maintenance as well, so im ruling out plugs/fuelpump. Does anybody have any idea? I filled up again and it seems as though I'll be getting about the same mileage out of this tank as well. I fill up a the same gas station every time and I run 89 octane. Cars a 2012 2.5L 5 speed.


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## G I Jew (Oct 10, 2011)

Depending on where you live, they could be switching from winter to summer fuel mixtures. Colder places will have more violent difference between mixtures.


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## watercooledfool (Dec 4, 2012)

the wider the wheel, the worse your mpg will be.


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## [email protected] (Feb 3, 2014)

Somehow I doubt that adding wheels that are 8.5 wide instead of 6.5 wide, will decrease MPG by 2-3 or 40 over life of a tank.


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## thygreyt (Jun 7, 2009)

[email protected] said:


> Somehow I doubt that adding wheels that are 8.5 wide instead of 6.5 wide, will decrease MPG by 2-3 or 40 over life of a tank.


i agree. i went from 225s to 245 wide wheels, and MPG remained somewhat constant.

temperature could be a factor... or fuel mix, as stated above.

For temp to work against you, it would have to be much colder than before for pretty much the duration of the tank.

Other than that, im out of ideas.


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## [email protected] (Feb 3, 2014)

Weathers been kind of warm, then cold. I dont think its weather. Ive had the car 1.5 years and have never had less than 320 to a tank....and I clear the odometer EVERY time I fill up. Im OCD about it. In the past month I have done a roof rack, fairing, coilovers and didnt notice much of a delince at all. I put the wheels on last Monday and boom...lost 40 Miles per tank of gas. Im going to see what I get out of this tank but as of now, my Odometer is reading 127 and im almost at a half tank.


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## thygreyt (Jun 7, 2009)

fack, thats bad.

i honestly have no idea.. and i too am OCD about my fuel economy. i have a spreadsheet with every fuel up since 2010 lmao (and every mod/time)


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## [a]bek. (Jul 21, 2012)

If you've ruled everything out, put the stock wheels back on, ride a full tank and see. if its not that, then you've got something else on your hands.


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## greekunit690 (Sep 9, 2013)

I have the exact same problem...put 18x8.5, 9.5 in the rear and noticed a drop from about 360 to 310 if I'm lucky. No change whatsoever in driving habits...my guess would by the wheels

Sent from my SGH-I337 using Tapatalk 2


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## gugu1981 (Jul 25, 2011)

someone has mentioned rotational mass in a previous thread. I am not sure of the technical details behind it, but figure i'd share it anyways.

I have been slightly worried about this for when i go bigger and wider, but then always have been justify it by remembering that I drive the car 1500-2500 miles a year. I have a motorcycle to commute on, and that gets 40+ no matter how hard i twist the throttle.



Peter


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## Rabbid Rally Rabbit (May 5, 2013)

[email protected] said:


> Weathers been kind of warm, then cold. I dont think its weather. Ive had the car 1.5 years and have never had less than 320 to a tank....and I clear the odometer EVERY time I fill up. Im OCD about it. In the past month I have done a roof rack, fairing, coilovers and didnt notice much of a delince at all. I put the wheels on last Monday and boom...lost 40 Miles per tank of gas. Im going to see what I get out of this tank but as of now, my Odometer is reading 127 and im almost at a half tank.


Honestly, this sounds like your new, porky wheels, grippy tires, the fuel changeover and your right foot combined into an MPG-killing mess. 

From personal experience, I know for a fact I push it harder when it's nice outside, and my 245s are definitely not LRR --around town I get ~28-30 when I'm not having fun, but ~24-26 when I'm playing.


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## watercooledfool (Dec 4, 2012)

[email protected] said:


> Somehow I doubt that adding wheels that are 8.5 wide instead of 6.5 wide, will decrease MPG by 2-3 or 40 over life of a tank.


Yeah, I really meant wider tires… they have to have some effect on your MPG….are they new tires or older?


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## [email protected] (Feb 3, 2014)

Tires have a few hundred miles on them.


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## Rabbid Rally Rabbit (May 5, 2013)

[email protected] said:


> Tires have a few hundred miles on them.


They sticky or LRR?


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## le0n (Jun 12, 2013)

I lost 5mpg when I switched to 225/18 from 215/16.

I used to average 450 miles between fill ups. Best tank was 475 miles.

It's tough to even get 400 miles before needing gas now.


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## j0rb (Sep 17, 2011)

I think it's the wheel tire combo. I'm on 18x8.5 with Continental DWS's. For my normal commute I am pretty consistently around 25 mpg. On my last long distance trip I got just over 30 mpg.


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## Rabbid Rally Rabbit (May 5, 2013)

j0rb said:


> I think it's the wheel tire combo. I'm on 18x8.5 with Continental DWS's. For my normal commute I am pretty consistently around 25 mpg. On my last long distance trip I got just over 30 mpg.


I think it's because he's running stickier tires on heavier wheels. Grip comes at the cost of milage --just the way it is...


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## le0n (Jun 12, 2013)

My 16s were yokahama s-drives, now my 18s are toyo proxes.

The 16s were even on old Mercedes wheels that were pretty heavy.


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## Rabbid Rally Rabbit (May 5, 2013)

le0n said:


> My 16s were yokahama s-drives, now my 18s are toyo proxes.
> 
> The 16s were even on old Mercedes wheels that were pretty heavy.


Side note: I would totally rock old Benz turbo 16*8s w/ 255s if I could find some. That'd be a killer rally wheel...


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## le0n (Jun 12, 2013)

Rabbid Rally Rabbit said:


> Side note: I would totally rock old Benz turbo 16*8s w/ 255s if I could find some. That'd be a killer rally wheel...


still off topic:
here's what they looked like, great setup for hyper-miling








*
back on topic*: Dave, what brand/type of tire did you go with?


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