New Wheels vs. Expected MPG Loss

Actually I'd like to take credit but 32kcolors called the 43mpg. i actually thought you would be at about 45-46mpg because it is a GenIII. A lot of that could be your driving habits too so real numbers are tough to estimate. Even at 43mpg you're still getting stellar mpg and the car looks great.

 

I only increased the weight by approx 2lbs per corner over the OEM 15" with my combo (17" x 7" with Conti DWS tires) and lost 3MPG. I thought I would be able to do better than that since I was only adding 2lbs per corner. I think the width of the tire plays a bigger role than the unsprung weight in the total MPG loss.

I can still get 51-52MPG (computer) on my round trip commute (66 miles) but my overall average is 47 MPG since our local drives involve a lot of small hills. I have found actual MPG to be about 2MPG less than the stated computer MPG.

 

I agree. The weight of the wheel is important but more important is the tire compound an design and the overall dimensions of the tire. A wide tire is going to increase the contact patch and produce more friction and thus raise rolling resistance. An aggressive performance tire will be sticky and produce even more friction. Finally, a wide tire also increases frontal area and will raise effective coefficient drag. All of this combined will dwarf the losses due to increased wheel weight in my opinion.

As you have noticed, the wider, heavier tire and heavier wheel effects stop and go driving much more than sustained speed driving (highway). So for those with mostly highway commutes, the wheel/tire upgrade won't lower MPG as much as someone who spends most of their time driving in stop and go traffic.

 

Update: with my 225/40 R-18's I am getting 49.1 on the current tank with about four bars left on the fuel gauge. :rockon: On my trip B, I am at 44.6 for the past 1093 miles. This probably can be attributed to several things.

1. There is now 3500 miles on my car-I have been combing through the forums and the consensus is that the car comes into its own between 3-6K miles. My mileage has been increasing with each tank.

2. I watched the Youtube video posted elsewhere here on PC and have adopted the P&G method of driving the car. I rarely turn on the cruise control now around town-using it appears to actually decrease fuel economy which is counterintuitive to what I know to be true with traditional ICE cars.

3. Increased the PSI of the tires. When I had them mounted, Discount Tire inflated to 35psi and the tire's max is said to be 42psi. I have put 45psi in with the tire being completely warmed up (about an hour of continuous driving @ highway speeds).

4. Warmer weather here in NM. I bought my Gen III, in February.

Can't wait to get some Conti's on it.

So, it looks like the loss of MPG is not nearly as bad as I initially thought. What I have learned with the wheel/tire combo is truly that YMMV....

 

That's great news Randy. I posted up a LRR 18" tire but I think it is a 235 width which may counteract the benefit of LRR if you go wider than you currently run.

 

When I upgrade to the Conti DWS's I am going to put 215/35's on it. A little narrower and better LRR. That should help too.

/randy

 

Ran these three sets so far:

Stocks: 56 avg mpg
15" Drags: 61 avg mpg
19" Kyowas: 51 avg mpg