Prius II,III,IV vs. V Fuel Economy

The honest answer is that I just know this because I live EU . The official test data is the only thing the car manufacturers are allowed to quote. Here are the UK numbers (the site does not mention the tire size so you just have to take my word for it, or look it up):

17" Prius (T4)
VCAcarfueldata.org.uk - Search Results - Further Information

15" Prius (T3)
VCAcarfueldata.org.uk - Search Results - Further Information

PS I would save 1.82€ per year if I would change my tires from 17" to 15"... aint gone happen

 

I just swapped my stock tires for the 2010 Prius II to 17" rims. In the past, I was able to pull off around 54mpg with stock tires, but now I can barely hit 47. This drop seems significant.

So, according to many postings on the thread, I should expect around 2~3 mpg drop going from 15" to 17". I don't know there the other 5mpg goes.

Just wondering, does anyone know whether ambient temperature affects mpg? The only thing different aside from swapping the wheels is that the weather got a lot colder in CA since I got my Prius in March.

 

Thanks for the insightful reply. The temperature here in the SF bay area dropped from around 70~80 to around 40~50 in just 2 weeks. I do not turn on the heaters nor do I put on winter tires. For tire pressure, I check regularly and is at recommended levels. So, with that said, I lost 5mpg due to winter fuel blend and temperature drop? Is this what other people on this forum typically experienced with temperature drop?

I'm asking because:
1) I ordered pre-mounted and balanced wheels from wheelsnext.com. I don't know if they did a good job mounting/balancing the wheels ...
2) I just went to the dealer service for my maintenance, and I asked them to install my new wheels and replaced engine oil. Hope they didn't do anything to screw up my mpg ...

I've enjoyed a steady 52~54mpg so far, it's a bit hard to live with < 46~48mpg now ... I'm sure many Prius owners can understand =D

 

Also from the SF Bay Area - I saw a 4 to 5 MPG drop in my last two tanks that I attributed to the Winter fuel blend.

 

Thanks for the reply. Oh wow. I guess I should be relieved that it wasn't some mechanical mishap. But 5 mpg drop due to winter fuel blend ... who'd ever thought it would be this significant?

I wonder, does the EPA ratings come with the disclaimer that the 51mpg for Prius is characterized with none-winter blend? I can imaging people who bought Prii at northern states during winter cratching their heads wondering why their mpg is at 45 when EPA rated it at around 50.

 

Why would there be Higher MPG when the car is hot. And what's the deal about blocking the grill?

 

1. Internal combustion engines are more efficient at normal operating temperatures and above than below.

2. Partially blocking the grill speeds engine warm up and improves aerodynamics.

 

Another possible factor: the 17" tires rotate about 2% more revolutions in any given distance. The OD's a little smaller.

 

Toyota doesn't distinguish between models for MPG purposes in the US. Toyota UK released a doc that does (try a search--this topic has been discussed a bunch ), and from memory, the 17" wheel model had ~2% lower MPG--a rounding error.

 

Colder temps take a huge toll on mpg. My 2000 Insight 5 spd could do 70 mpg easily May to Sept and drop to high 50's for the winter. Giving a Lifetime mpg of 62 for 265,000 miles. The 2010 Prius II gives me a solid 60 avg May to Sept, but is already down to 55 mpg in November and I have not even put the snow tires on yet. I expect low 50's avg for the winter, giving a likely 55 mpg lifetime. Between cold starts, m.ore tire resistance from the snow tires, plowing thru snow and slush, more heater use, etc - its a big mpg hit.

 

My V has dropped from 57mpg to about 52.5 as the weather has gotten colder. My drive home still is around 55F, but the closer that gets down to the 30-40F range, I think the lower it will get. I'm going to guess lowest it will get this winter would be 50-51.

 

I agree with this. To save the cost, I think the Prius o meters in type II and V are the same. That is the reason why type V Prius (17 inch rim) owners see lower in mpg but actually they are the same mpg.

 

If tire diameter / odo cal was the real reason for a difference, V owners would be computing higher MPG because their odos would be reading 2% higher than actual distance.

Actually, this cannot be true. Some auto makers (e.g. Honda and Subaru) have been hit with class action lawsuits about warranty fraud because their odometers read too high. The settlements made allowance for 2% error. Any car maker that designs in this problem post-Honda-lawsuit is an idiot.

 

Yep on Tideland's answers. Many Factors Affect MPG covers much of this as well and Why does mileage drop in winter? &mdash; Autoblog Green goes into some more detail.

 

That sounds about right.

There was a very old thread from around the introduction or when the 2010s first shipped which explained why you couldn't get the solar roof w/Prius V (has 17" wheels) due to additional weight. Essentially (IIRC) it would've forced Toyota to have publish different mileages for the US for 17" wheel vs. non-17" wheel versions.

edit: The above has been discussed/debated a lot in the past. http://priuschat.com/forums/gen-iii...prius-option-packages-naias-5.html#post786779 was an official answer from Toyota.