CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

2018 Cruze drastic decrease in fuel efficiency

I purchased an aftermarket set of 18” wheels w/ new tires to replace the factory 16” wheels. Overall tire height and width are still the same but fuel economy decreased by an overall average of 10 mpg. It’s always averaged between 38-40 mpg. Now it averages 26-30 mpg. Even if the new wheels weigh a little more should it affect the fuel economy this much? Also, ever since I got the new wheels, the car shakes just a little bit when reaching speeds over 74 mph. It’s a very mild shake but can still feel it. The tire balance has been checked twice by two tire shops and they are perfectly balanced.

Now you know why it is not a good idea to change tire’s and wheel’s from factory spec’s.

some Cruze Premiers come with the same factory specs as the 18” wheels and tires that I purchased aftermarket so why would it be any different. mine is just an LT but same engine and everything. so doesn’t make any sense.

If they’re very heavy rims this might happen.

Not sure what they weigh since I never touched them. The weight may be the cause of the decrease in fuel economy. But still can’t figure out why the car still shakes slightly at higher speeds.

Could be a bad tire. What brand tires and wheels?

First, the OE tires (the tires that came on new vehicle from the factory) were designed with fuel economy at the forefront - and they get that by sacrificing treadwear and traction (especially wet traction). Most replacement tires are designed for either wear or grip and those will not have nearly the fuel efficiency of the OE tires.

Second, new tires don’t give as good of fuel economy as worn tires - all other things being equal. So that’s a second hit in the FE department.

You didn’t tell us what the UTQG rating was of both tires, but I’ll bet you went towards better wear, so you took a third hit.

You also didn’t tell us what tire sizes you went from or to, and that can have an effect as well.

Yup, you should be seeing a loss of fuel economy, and depending on what you did exactly, the loss could be quite large.

3 Likes

The effects of wheel/tire weight on HP at the wheels. Fuel economy would also be reduced, although this article does not address that. To get the familiar amount of acceleration you’d have to have the gas pedal pressed down more now. Not good for MPG!

https://books.google.com/books?id=Y7P6BFss_0cC&pg=PA24&lpg=PA24&dq=understanding+wheel+weight&source=bl&ots=vC2UL47Mq-&sig=FX4EEXhGP_htzZLe2tNGrGVFYFA&hl=en&sa=X&ved=0CFcQ6AEwCWoVChMI-K6Kr6DsxgIVTTKICh3SLg0z#v=onepage&q=understanding%20wheel%20weight&f=false

Car and Driver found about a 10% hit to mpgs when testing high quality tires and wheels. We don’t know what the new tires and wheels are in this case:

Factory tires were Hankook Kinergy GT 205/55R16. New tires are Cosmo MuchoMacho 225/40ZR18.
ESR SR12 wheels
I did expect maybe a slight decrease in FE but not this much for both city and highway driving. Even at lower city driving speeds it’s only averaging 25 or so when it used to be 35

There is no way I would tell anyone I put ’ MuchoMacho ’ tires on my vehicle .

I did a little online research and there is no reason to purchase these ultra cheap tires except for a junk vehicle you want to get rid of. I would not trust these things at turnpike speeds at all.

2 Likes

I think its because of the garbage tires. Just my opinion.

If those aftermarket wheels don’t have the right amount of offset they can add a tilt to the hubs, changing wheel alignment and adding stress to the wheel bearings.
Modding a car is like playing table games in a casino: best to not play the game if you don’t understand the rules!

I read up on it before hand and hadn’t read about anyone having any problems with aftermarket wheels on this car. And I made sure to keep the tire size, wheel size and offset the same as the 18” factory wheels that come on the premier trim models. And yes I should’ve researched the tires more I admit that. I just asked the tire guy to order me some tires that weren’t cheap but I didn’t want anything super expensive either. Told him to get something in between and he told me these were good tires. Charged me $150 each for them. If these tires are really that crappy maybe I should give him a call…

Is it too late for you to return the wheels and/or get your old wheels back?

Being a 2018 car, I’d wonder if this is still in the factory warranty period.If you have any sort of suspension or related issues, the dealer might could blame the non-OEM wheels.

Even if you have to eat the cost of the 18" tires, you might be better off. Just a thought.

Yes it’s still under warranty and I still have the stock wheels and tires. I kept them just in case I had any issues I could throw on the factory wheels so warranty won’t be voided

@CapriRacer Do you want to make a statement about these Cosmo tires as you are the tire expert ?

Yeah, but they aren’t the same wheels. If yours are heavier, and/or have more of the weight toward the rim rather than the hub, then you’re making your car work a lot harder to spin them. And btw, the Cosmo tires weigh 6 pounds more than the Hankooks did, so that’s 24 more pounds, all the way on the outside of the wheel which is the worst possible place to add weight, that your car is having to fight.

As to why it shakes slightly, either a bad tire like @texases said, or bad balancing. Low-profile tires often require roadforce balancing in order to get the balance right. A normal balancer won’t do.

3 Likes

+1
Those are truly GARBAGE tires.
Take a look at this:


:+1:

Well, I agree that they’re most likely garbage based on the price and the fact that they seem to be putting a lot more thought into marketing and appealing to teenagers than into things like, you know, tread and construction.

But that article is pretty stupid. “I don’t know anything about these tires and I haven’t actually tested them but I’m purdy sure they’re gonna suck because they have stupid names and don’t cost much” is the essence of what he’s saying.

1 Like