Gas mileage after putting on aftermarket wheels??

[Beau2424]

Hey everyone, i just recently bought my 2011 geny 4.6... Had the 18's with 235/50's on there.. Was getting anywhere from 19-25 miles per gallon on a full tank depending on how and where i drove.. Well i just upgraded to aftermarket luxary Roderick rw3 19's... Running staggered setup with 275/40/19 on rear and 245/45/19 on front.. Well so far im getting 13-15 mpg so far thru half a tank... Albeit more in town driving on this tank but to have such a major difference in mpg scares the s..t out of me.. Lol.. Is there something that needs to be tuned in the computer to asjust for bigger wheels and tires?

 

[Mark_888]

Using a tire size calculator (Google) can you tell us the percent difference in overall tire diameter between stock and after-market?

 

[Philth]

Your wheels are most likely heavier and wider. Probably isn't much you can do.

 

[Mark_888]

I did the tire calculator for you, and there is not a big difference in size between stock and after-market tires (based on tire size, not wheel size). But your new tires are larger, so it looks like you are getting about 1.5% better mileage than the car MPG indicates (I calculated that based on fewer revs per mile on the after-market tires). Since that may not account for all of it, it must be what Philth said, and also maybe your new tires are designed to be very sticky for good traction and cornering, but no so good for getting better MPG (based on rolling resistance).

 

[QuantumRift]

In a nutshell, you went from an 18" wheel to a 19" wheel. You would have to do the calculations to see what percentage your odometer and fuel consumption calculations would be off. A 1" difference in rim diameter rim will result in a larger circumference at the tire surface (the tire has to be included as well).

So in a 'mile' the tires will make less rotations than a stock tire to cover that mile, and the displayed MPH will be off as the computer has not been reprogrammed to know the right size of tire. So your actual speed will be a bit more than what is displayed on the speedometer. And your fuel economy calculations will be off by the same amount that your speedometer is off (for the good, you'll show that you are getting better fuel economy)

BUT.......

Having said that, it would appear that your choice of tires and rims has more than offset the (fake) fuel economy caused by the larger-sized tires. Fuel consumption increases when you increase weight because it takes MORE fuel to accelerate the extra weight to speed. And in turn, you use more brake pad each time to slow down the extra weight.

SO, larger rims, and larger tires = more weight. I would have inquired about this before I took the step to install larger tires and wheels, as it is something I would take under consideration before I bought them.

And another big thing to consider is the ROLLING RESISTANCE of the tires you've chosen. Takes more fuel to push them down the road.

So in short, the larger rims/tires would have caused a slightly better perceived fuel economy, but the combined weight of rims and tires, and the wider tires with increased rolling resistance, have negated the perceived increase. So if you do the calculations properly, you may find that the fuel loss is a bit more than you actually see.

Of course, why complain about the fuel economy in a $50K car? LoL....

Now, I know that if I by my tires at Discount Tire, I can drive on them for 30 days and exchange them for something less fuel consuming. I think other tire shops have similar policies, but I don't know for sure.

 

[landtuna]

OP, you sure you're not stepping on the GO pedal a bit harder with the new skins?

 

[QuantumRift]

Now THAT'S one I didn't consider. LOL.

 

[Beau2424]

In a nutshell, you went from an 18" wheel to a 19" wheel. You would have to do the calculations to see what percentage your odometer and fuel consumption calculations would be off. A 1" difference in rim diameter rim will result in a larger circumference at the tire surface (the tire has to be included as well).

So in a 'mile' the tires will make less rotations than a stock tire to cover that mile, and the displayed MPH will be off as the computer has not been reprogrammed to know the right size of tire. So your actual speed will be a bit more than what is displayed on the speedometer. And your fuel economy calculations will be off by the same amount that your speedometer is off (for the good, you'll show that you are getting better fuel economy)

BUT.......

Having said that, it would appear that your choice of tires and rims has more than offset the (fake) fuel economy caused by the larger-sized tires. Fuel consumption increases when you increase weight because it takes MORE fuel to accelerate the extra weight to speed. And in turn, you use more brake pad each time to slow down the extra weight.

SO, larger rims, and larger tires = more weight. I would have inquired about this before I took the step to install larger tires and wheels, as it is something I would take under consideration before I bought them.

And another big thing to consider is the ROLLING RESISTANCE of the tires you've chosen. Takes more fuel to push them down the road.

So in short, the larger rims/tires would have caused a slightly better perceived fuel economy, but the combined weight of rims and tires, and the wider tires with increased rolling resistance, have negated the perceived increase. So if you do the calculations properly, you may find that the fuel loss is a bit more than you actually see.

Of course, why complain about the fuel economy in a $50K car? LoL....

Now, I know that if I by my tires at Discount Tire, I can drive on them for 30 days and exchange them for something less fuel consuming. I think other tire shops have similar policies, but I don't know for sure.

Thanks for the great info! I knew i was gonna take a hit with the mpg but wasnt expecting an 8-10 mpg hit! Ive always put on after market wheels and tires on all my vehicles and never notice this much of a difference.. Was hoping it wa the genesis coomputer that isnt reading right.. How would i get this fixed?(reprogrammed with right wheel and tire size)?

 

[Beau2424]

OP, you sure you're not stepping on the GO pedal a bit harder with the new skins?

Shhhhhhhh! My ol lady might read this!! In all seriousness we did some storm chasing tonight as we live by grandbury/weatherford/fort worth texas and had grapefruit/softball size hail bout 20 minutes out from us headed directly at us.. Multiple tornados everywhere.. Im sure yall will hear about it tomorrow... Crazy crazy!!! Anyways we jumped in the 4.6 an loope around the large storm cell through back county roads then main highway I20 and pushed this geny to the limit!! Was absolutel amazing at how the car was gripping the road and curves with this staggered setup and beefy wide ass rear wheels! Loved it.. Wife scared shitless but we made it aroun the cell and took some pics! Deaths already being confirmed...

Genesis handled it beautifully and i missed out on those big ass ice chunks falling from the sky!!

Pray for the area...

U can friend me on facebook as i have some pics of the storm/tornados

Mark Daiker

 

[landtuna]

WOW! Sorry to hear about the storm but glad you weren't hit. We had one of those a couple years ago and it shredded the trees pretty badly. There were lots of dented vehicles for sale for a long, long time. Nothing like softball-sized hail though.

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[Beau2424]

 

[Beau2424]

 

[Beau2424]

 

[GenesisCaptain]

I would give it some time. When I upgraded my previous cars from 16" to 18" and another car from 16" to staggered 18", I lost 1-2 MPG on both. I can't imagine that the Genesis would be any different and lose four times that. So, my hunch it was the driving conditions more than anything else. Revisit your mileage after you get over the new shoes honeymoon and resume your typical driving style.

 

[Beau2424]

K thanks for your input

 

[ockevin]

Nice set of wheels. Do you have a side straight shot of them ?

 

[Beau2424]

No not yet.. Will once i get them cleaned up.. They dont stick out passed the wheel well if you were wondering that..

Thanks for the compliment

 

[Beau2424]

Front rims are 8.5 with a 2 inch lip and the rears are 9.5 with a 3.5 inch lip..

Really wanted the 20's which the fronts were 8.5 with 2 inch lip but the backs were 10 with a 5 INCH LIP!!!! Would of had to run 245/40/20 on front and 275/35/20 on the back.. Was scared to lose too much ride quality by going to a 20.. As the wife was worried about that and also worried that, as in her words, would ghetto it up! Lol... But damn i wish i would of gotten the 20's..

But as usual i am sure the wife was right.. Ride quality with this setup is beautiful

 

[Beau2424]

 

[Beau2424]