Any compromise on MPG with Prius Five?

The 17 inch wheels with the wider tires also have more weight out away from the center of the wheel, the rotational mass, which contributes to lower mpg. Takes more power to get them going every time you accelerate.

 

Yup. IMO expect a 2-3mpg hit using the OE 17" tires and more using aftermarket 17" tires vs. OE 15" tires. It could be worse if you compare the 17s to a very fuel efficient 15" tire like the Energy Saver A/S. You may still be able to achieve 50mpg+ average if you drive slow enough and or have the right commute.

 

Yes 50+ MPG is doable, I have not went below 50 MPG yet in a year and a half, 28,000 miles my lifetime average is around 52.5 MPG. Like FL8 says if I hade the stock 15" wheels with LRR tires I should really kill and get in the high 50's to maybe even the low 60's MPG. My stock tires are non LRR Brigestone Turanza EL400-02's a more efficient 17" tire would also help to increase MPG's. One of these days I will acquire a set of OE 15" wheels and run some tests like FL8 and others have done.


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It's not unbelievable. The OE 17" wheels sport a deeper offset which keeps them tucked in the wheel well but the wider track sticks out further past the wheel spats so total drag should increase. A more flush mounted 17" should in theory decrease mpg even further.

 

IIRC, one/some of the members here have swapped between 15" and 17" tires on the same car running the same routes they usually drive. The conclusions have shown the 17" tires do result in a drop of 2+mpg in most cases.

I'm a conservative driver (big surprise for a Prius owner!) and normally get the advertised EPA MPG for most of my cars. In the case of my 2012 Prius Five with factory 17" wheels- my calculated MPG is 48.6mpg (50.6 via the dash display) for the three plus months I've owned it. I'm confident that with 15" wheels- I'd be averaging 50+ mpg like other Prius owners.
In any case- I drive about 18K miles/year and the 2mpg drop from the 17" tires will cost me an additional $54 in fuel for the year versus the standard 15" wheels. That really doesn't bother me cause I really like the look of the low profile 17" tires and alloy rims, the quicker turn ratio, the LED headlights and the heated seats and power driver seat in the Five.
I also went from a car that got 24mpg to one that gets 48+ mpg so my fuel costs went from $2775/year to $1387/year.

 

The only caveats that I have regarding my above posting are that, 1. I do live in the tropics with very similar weather each day (good for MPG)., 2. Supposedly we have E10 fuel here the pumps say fuel may contain up to 10% Ethanol, weather or not it does I don't know. If it does my MPG is pretty good with E10. I have run Ethanol free fuel for a couple of tanks in the past I did not notice much of an MPG increase so that makes me wonder how much Ethanol is actualy in the may contain up to 10% Ethanol fuel.


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According to Wikipedia-

Gasoline has an energy density of 34.20 MJ/L
Gasohol E10 (10% ethanol 90% gasoline by volume) has an energy density of 33.18 MJ/L

10 gal of Gasoline contains 1,294 MJ of energy

10 gal of Gasohol E10 contains 1,255 MJ of energy

If you get 500 mi out of 10 gal of Gasoline you'd likely get 485 mi out of 10 gal of Gasohol E10.

 

I agree with your conclusion, however, there is much more loss associated with 17s if you swap the OE 15s for more efficiency tires or use less efficient 17" tires. In the former case I am able to get nearly 10mpg better with the 15s because of my driving techniques. The average Joe could easily see 6+mpg more in the same situation. In this case the cost per year is much higher if you drive 20k or more a year. The lifetime cost could be a couple thousand more which just adds to the total cost of ownership for that package. Just things to think about. If I drove much less miles per year I would probably run 17s too.

 

I wanted to ask if their was a way to swap the LED lights on a five model for brighter lights? I find them to be ok but not as bright as I would like. I also never notice them auto level like they are suppose to do. Sorry if this has been asked before. What are the specs on the lights used on the five model?

 

Every late fall I've switched over from the 215/45R17 Micheline Pilot on stock 17" rims, to Michelin X-Ice2 in 195/65R15, mounted on Corolla rims. Then in early spring I do the reverse.

I'm keeping a tank-by-tank calculated mileage log. There's enough variety in our driving (trip duration/speed, who's driving, ambient temperatures, weather, and so on) that the mileage jumps around a fair bit.

Looking at the numbers it's hard to say with certainty, but my hunch is the mileage with the 15" snow tires is about the same as the stock 17" Pilot setup. I recall when I first got the snows the rolling resistance felt about the same, or even slightly better.

A further complication: the 15" has slightly larger O.D., close to 2% I think. I'd assume our odometer is set up to be accurate with the 17"'s.

 

A full retrofit with high end projectors will out-perform the LED setup on your car but it will cost ya. Projectors plus good bulbs alone could run $400+ then you have to have the parts installed which could run $400+.

Check out HIDPlanet.com and TheRetrofitSource.com.

Check out the crazy cutoff in this video. The video is dark but you don't get this kind of cutoff on the street without some seriously bright light!

 

It's more likely the oncoming driver is flashing you because they see a pair of lights on each side of your oncoming Prius, which makes them think you have your high beams on.

I used to get flashed all the time when I drove my Acura Integra, many years ago, with the foglights on. In that incarnation, Honda/Acura put the foglights in the headlight assembly, so driver's would think I was driving around with my highbeams on instead of the lows + foglights.

 

In part this is because they measure Cd slightly differently:

If you put your car in a wind tunnel and blow air over it to measure drag, the wheels are not turning. Measurements with the wheels turning will be different. One groups of Manufacturers (I think Japan but don't rely on my memory) has the wheels turning, while the other group (again I think Detroit but I may be wrong) is using a wind tunnel. The wind tunnel gives very repeatable numbers about a condition that will never really occur, while the test with the car moving is less precise, but more realistic.

So Toyota gets a Cd of .25 and Chevy gets a Cd of .30, using different tests. (and perhaps different trim levels)