Winter Vs. Summer MPG

It depends on your tires. With the Original Goodyear Integrity tires, my MPG went down about 15% (47 warm vs 41 cold). Michelin MXV4+ Energy Saving tires (LRR) reduced the difference to about 10% (saving about 0.5 MPG overall, 47 vs 43). Now I have Nokian WR tires (also LRR). They also hold the difference to about 10%, but seem to do a little better both winter and summer than the Michelin's.

This is from over 4 years of data (see attached Excel file) and 120k miles of happy Prius driving.

JeffD

 

It depends on where you live. I don't see any difference between the winter and summer months ... but then we don't have a winter season here in Paradise.

 

Hi crazi...,

It also depends on your traffic. My winter mileage is very similar to jdenenburg (traffic is lower), but May through November is at a minimum 58 mpg over a tank average, to as much as 63 mpg. I am at 66.2 mpg right now after a week of driving, and the weekend errands. Presumbably this is because of the pulse and glide oportunities on the crowded drive home interstate portions of my commuting.

80 F, overcast and humid is about the best conditions for fuel economy in a Prius. Which describes much of the late spring here in Chicagoland. Although those 30 plus mph head winds put the kaibosh on the mileage sometimes.

If you have very very low traffic, you can more readily hypermile, which is the opposite of my situation- where traffic slows down the speed of cars. The people on here that are gettting the best mileage have rural 2 lane routes to and from work near bodies of water. They then do 50 mph super highway mode (at 65+ mpg) or pulse up to 40, and glide down to 20 mph, or glide down a hill at 40 (good for 80 mpg).

But too much traffic, like stop and go in a nearly grid-locked inner city is very bad for mileage too. Which is really bad when its like -5 F outside and one gets into stop-and-go right at the start of the trip. And then one is lucky to get 25 mpg while one is in that traffic.

 

If you live in Minnesota, you'll probably see a bigger difference than if you live in Maryland. So tires might be a bigger issue in Minnesota.

 

If you block the grill properly, (and install a scan gauge to monitor temps) you might see little if any drop in the winter. Without thinking we get~52 year round, and if we really try we can push ~60.

Use the search function and read all you can about grill blocking.

Icarus

PS. It is ~70f and we still have the grill blocked except on slit. Engine temps NEVER exceed 185f in normal hwy/city driving.

 

Hi Crazi...,

Again, it depends on temp. But also grill blocking. And there is also interior versus drive train warmup. The interior warm up is pretty quick, less than 5 minutes. The drive train is a different situation, and my worse case in the winter, without grill blocking its takes about 15 miles of a 22 mile trip, or about 25 minutes. And even then it still is not the same operating condition. It takes a 35 mph speed after a start a to get into a glide in these conditions. With the 90 % grill block this is knocked down by half. I only use the block heater when its below 10 F, as I do not have a private garage. Those with a garage and a block heater on a timer can reduce these times one half again.

This week however, at 60 F morning temps , and the battery warm from the day before, it took less than 5 minutes / 2 1/2 miles (constant 35 mph, plus two stop signs) to get to stage 3a, this with the top grill blocked, and the bottom grill blocked 50 percent. And then to get past the stage 3b follies and onto full stage 4 it took another few minutes, but only another mile (stop lights). We have had temps up to 90 F, and this grill block has been fine (92C max coolant temps seen).

In the evening the times are problematic due to traffic. But the miles driven are similar. Even though the temps are warmer in the evening, the longer periods of stop and go increase warmup mileage that would occur otherwise.

One of the issues with warmup is slow constant speed driving below 35 mph, or without a stop. These are the signals that allow the car to change from stage 3B to full hybrid stage 4. Staying in stage 3B for a long time is a big gas waster. I have pulled over to the side of a residential street to wait for the engine to stop to get past this. If you cannot get the car to glide on an route you do not normally take, below 35 mph, after 3 miles of continuous summer driving, you might try this. I notice this more now as a I have a temperature indication, and see the car at 80 C, but no glide being allowed.

 

Which is more valuable (if you had to choose) betwen the block heater or blocking the grill? Also with the block heater do you have any suggestions on what brand of timer works best?

 

In California MTBE is blended into the gas during the winter to help reduce smog levels (ozone I believe).
Anyway, when the MTBE blended gasoline is no longer available (around May-June), my mileage goes from 44-46 to 48-50 mpg.

 

I do. Here's my data:



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The blocked grill retains heat. The block heater brings the 1st 5-10 minute performance up to average. With the grill blocked my lifetime average increased over the winter. Insulation is cheap and easy to install. It all depends on your environment.