Scion TC wheels on a Prius

I put Scion 17" wheels and 215/45/17 Michelin Primacy LRR tires on a couple of weeks back. I have been getting 42-43 MPG on the past 3 tanks. My best tank with the stock tires was 51MPG...def lost some MPG but it looks way better IMO.

 

That has been my experience with 2 different models of tires. At least you'll get better mpg this summer.

 

I have the plus pkg 17" wheels and I average 47-48 mpg per tank. I dont see much loss at all.

 

And what did you average with the OEM 15" wheels?

 

Because of the cold(er) weather in Seattle over the past couple weeks I was only getting about 42-43mpg with my non-LRR Conti DWS's....but that's running 42/40 psi. In the summer I would get anywhere between 46-50 based on how aggressive I was driving.

 

He doesn't have OEM 15", as do all Five/Plus owners. A loss of 2-3 mpg sounds about right for the Gen III if we take 50 mpg actual as a reference. Certainly not as large of mpg hit as you seem to get in your Gen II.

 

I know. I was being sarcastic.

 

I had a rental gen 3 for two days while my leather was being installed...I got 49 mpg on the stock 15's. I drive alot of freeway miles at 75 mph...so not too slow.

 

Too many variables when you switch cars, Kevin. If you could swap to a set of OEM 15s and do a fairly rigorous test I would give you more credibility but your only experience is with your awesome but OEM 17" wheel equipped car and a rental.

I do believe the GenIII suffers less of a loss than thenGenII. If you perform zero hypermiling techniques like gliding then the difference between 15s and 17s becomes even smaller. The 15s offer a much high ability to glide long distances which is why I used to observe only about a 4-6mpg difference whereas now I can observe as high as a 8-9mpg difference if I really try. My best tank on the Kumho ecsta ASX 215/45/17 was around 51mpg after they were pretty worn. With the new Primacy MXM4 I've maxed at 50.2mpg but to keep things honest the new tires have way more tread. The best tank on 15s was 62mpg (I think Nokian i3).

One other value to consider is the error in reporting mpg. Both sets of 17" tires I have owned were larger in diameter than my 3 sets of 15" tires (Integrity, Nokian i3, dB Super E-Spec). This should in theory produce artifically lower mpg numbers with the taller tire but I cannoth determine how far off it would be and I'm not ready to try and figure it out yet. I think a shorter tire would be the best choice for mpg reporting but now comes the really intriguing question...... Which is more accurate, the mpg with the OEM tire or the mpg with the larger aftermarket tire? Be careful with this one and remember that the OEM tire is rather short and the speedometer reads 1-2mph too fast in the GenIII and 2mph too fast in the GenII. The taller aftermarket tire corrects this error over 40mph so the speedo, GPS and Scangauge agree.