Gas Mileage with 18s vs 20s

[jmcgriff19]

I am a new member to this forum but have been reading on here for a couple months now. We are looking at purchasing a 2013 Explorer XLT FWD for my wife. Right now she has a Tahoe with 20s on it and the gas mileage is a couple mpg less than my mom's identical Tahoe with 17s. I have driven both of them to compare the mileage on the same roads and the larger heavier wheels is the only culprit I can come up with. Now that we are looking at an Explorer, I really like the look of the 20s, but I don't want to take a hit on the mileage just to have these wheels. If we are going to take a hit on the mileage for the 20s we will just stick with the 18s. Can anyone tell if the mileage is any worse with 20s vs the 18s on the new explorers?

 

[machine4321]

Over all, rotational mass will make a huge difference. Now the question is, since the overall diameter should be the same, how much more does the thin tire/large rim weight vs the smaller rim/more tire?

I suspect it is pretty close. But if there is a difference in MPG between 2 models then that would be my only guess.

 

[peterk9]

I am a new member to this forum but have been reading on here for a couple months now. We are looking at purchasing a 2013 Explorer XLT FWD for my wife. Right now she has a Tahoe with 20s on it and the gas mileage is a couple mpg less than my mom's identical Tahoe with 17s. I have driven both of them to compare the mileage on the same roads and the larger heavier wheels is the only culprit I can come up with. Now that we are looking at an Explorer, I really like the look of the 20s, but I don't want to take a hit on the mileage just to have these wheels. If we are going to take a hit on the mileage for the 20s we will just stick with the 18s. Can anyone tell if the mileage is any worse with 20s vs the 18s on the new explorers?

Welcome to the Forum jmcgriff19.:wavey:
Technically a 20" tire will cover a set distance in a shorter time that an 18". The smaller one would have to make more revolutions to cover an identical distance. An 18" would travel 703.30 revolutions/mi and the 20" 692.42/mi. I would say that you probably won't notice too much of a difference in mpg between the two since the 20" is also a little wider and heavier. The diameter variance is 1.57% which is well within the commonly accepted 3% max. With the 20's if your speedo read 60 mph you would actually be doing about 61 mph.
I replace my 20" wheels with the Explorer base model 17" (245/65R17) wheels for Winter and the difference is 1.66% which means at 60mph I would actually only be doing about 59 mph.
Unfortunately I can't really comment on fuel consumption since one set is used in cold weather which really affects mpg and the other is used in warm weather. Having said that, if both were used in the same weather conditions I doubt you would see much of a difference in fuel economy.
Not sure if that helped or confused you more, but good luck and happy shopping.

Peter

 

[Dr Plastic]

Actually the XLT comes with 245/60R18 tires which gives you 682 revs per mile with a circumference of 92.9" and the optional tire being a 245/50R20 with 680 revs per mile at a circumference of 93.1". That makes the 20" tire being .2% slower than the stock 18" tire. Your speedo reading will indicate you are going 60 mph but you are actually traveling at 60.1 mph.

http://www.miata.net/garage/tirecalc.html

With that all being said the switch to a larger rim will not make a noticeable difference as long as the overall diameter/circumference of the tire is no greater than 2% of the original. If you adhere to this you will not see a noticeable difference in MPG's

 

[peterk9]

Actually the XLT comes with 245/60R18 tires which gives you 682 revs per mile with a circumference of 92.9" and the optional tire being a 245/50R20 with 680 revs per mile at a circumference of 93.1". That makes the 20" tire being .2% slower than the stock 18" tire. Your speedo reading will indicate you are going 60 mph but you are actually traveling at 60.1 mph.

http://www.miata.net/garage/tirecalc.html

With that all being said the switch to a larger rim will not make a noticeable difference as long as the overall diameter/circumference of the tire is no greater than 2% of the original. If you adhere to this you will not see a noticeable difference in MPG's

The site I used was 1010tires.com.
The tire I looked at was the 245/60R18. It shows circumference of 92.91 inches and revolutions as I stated of 703.30/mi. Which ever it is, I'm not going to go and count them myself. The optional tire for the XLT is a 255 not 245 (P255/50R20 A/S BSW tires).

Peter

 

[Dr Plastic]

DOH...fat finger! Yes you are correct....with that said it is a 1.6% difference. anything under the 2% is OK! Thanks for the correction!

 

[1995E]

Welcome to the Forum jmcgriff19.:wavey:
Technically a 20" tire will cover a set distance in a shorter time that an 18". The smaller one would have to make more revolutions to cover an identical distance. An 18" would travel 703.30 revolutions/mi and the 20" 692.42/mi. I would say that you probably won't notice too much of a difference in mpg between the two since the 20" is also a little wider and heavier. The diameter variance is 1.57% which is well within the commonly accepted 3% max. With the 20's if your speedo read 60 mph you would actually be doing about 61 mph.
I replace my 20" wheels with the Explorer base model 17" (245/65R17) wheels for Winter and the difference is 1.66% which means at 60mph I would actually only be doing about 59 mph.
Unfortunately I can't really comment on fuel consumption since one set is used in cold weather which really affects mpg and the other is used in warm weather. Having said that, if both were used in the same weather conditions I doubt you would see much of a difference in fuel economy.
Not sure if that helped or confused you more, but good luck and happy shopping.

Peter

However, if you look at this MotorTrend review... comparing the Edge Sport versus the SEL

http://www.youtube.com/watch?v=J9Hbmtkpp7A

Wheel diameter does have a certain effect with performance. The amount of energy you need to put in for a 20 inch wheel versus and 18 inch wheel takes much more. Eats a bit of the MPGs but I think if you're going to be cruising straight paths versus going up and down hills, the 20's would be okay. However, driving habits count, maybe your wife mashes the pedal more. If you look at Ford's Fuel Efficiency bar, it makes a big difference when putting your foot down even the slightest for acceleration. These are big cars, and accelerating takes up the most fuel, and 20's are not good in acceleration. Especially not 22's. It's your pick though.

 

[Dr Plastic]

True. I think the one main difference between a 20" wheel vs. an 18" wheel is unsprung weight. The 20" wheel package is inherently heavier and there for will require more power to turn. tire/wheel weight is very important. this is why racing wheels and tires are much lighter than street wheels. I had installed a set of 18" x 8.5 OZ Superturissmo on my 2002 VW Passat W8. each wheel only weighed 17 lbs VS the stock wheel weighing in at just over 25 lbs. I swear that car handled and just overall drove better.

 

[Edgieguy]

Even in the extreme case of the Edge Sport with the 22"s vs the SEL with 18"s the difference is only 2mpg. And think about this... The forged aluminum 22" wheels on my sport weigh 39lbs each!!!!

 

[13TuxedoSport]

there is virtually no difference in highway MPGs between the 18 and 20 inch wheel. City, or a lot of stop and go, maybe a slight .2mpg difference in the 18 inch wheel, since the 18 inch wheel doesn't have as much rotating mass to get moving.

 

[jmcgriff19]

Thanks everyone. The overall tire height should be the same with either the 20s or the 18s, so it is just the additional rotating weight I am worried about. I am leaning more toward the 20s right now though. Does anyone know what the weight difference is between the factory 18s and 20s?

 

[13TuxedoSport]

Honestly, if fuel mileage is that much of a concern, a Fusion Hybrid would have solved that problem. .2 (if that) differnce in MPGs shouldnt outweigh the look of a 20" vs an 18" wheel. Long term the 20" will cost more. Initial cost plus replacement tires are more than an 18".

 

[peterk9]

Honestly, if fuel mileage is that much of a concern, a Fusion Hybrid would have solved that problem. .2 (if that) differnce in MPGs shouldnt outweigh the look of a 20" vs an 18" wheel. Long term the 20" will cost more. Initial cost plus replacement tires are more than an 18".

As I've posted in other threads, had the 17" wheel been an option for the Limited, I would have taken them. Cheaper to replace the tires and less worry about rubbing the rims against curbs etc. I believe that is one reason the manual states Explorers with 20" wheels are recommended to not be taken off road.

Peter