Winter MPG Drop!

Yes, it's true, the MPG drops with cold weather (mine goes from around 50 in summer to the low 40s in winter). But this is true of any car, since an internal combustion engine is much less efficient when cold. You just notice it with the Prius because of the handy MPG display.

Also, batteries are less efficient (have a higher internal resistance) when cold. But I suspect that the MPG effect of a cold NiMH HV Prius battery is pretty small compared to the MPG effect of a cold ICE.

 

The air is also denser when cold, hence more drag = less MPG

 

I have insulation on the engine and the grill blocked. It does help a little. Keeping the heat off around town and turning it on when on the highway helps more. But man that's cold!

 

Yep... an engine block heater will help too but it's not nearly as cheap as blocking the grille. As for only turning on the heat while on the highway, I turn it when I need to do harder acceleration or above 42 mph. At that point, the ICE must run anyway.

 

In the US, winter blend Gasoline is different than summer blend. (in winter you want gas to vaporize easier and need not worry about vapor lock as much) The Prius seems to prefer the summer blend.

The Oil Drum | The Switch to Winter Gasoline and a Primer on Gasoline Blends

 

In the old days, all cars preferred the summer blend for fuel economy, because it had higher energy density. I haven't kept up with any recent changes.

As for the higher air density on cold weather, that does more than just increase air drag. It also increases part-throttle engine pumping loss. But this has more impact on non-hybrid Otto cycle engines than the Atkinson cycle engines in most hybrids.

 

Absolutely normal. It's happening to every other car on the road, but even more so for them. There's no need to worry or do anything about it unless you want a new hobby :_>

Well, you do need to check and maintain the tire pressures at least monthly.

 

I notice a significant drop. During the summer I hit 69 mpg... 54 or so at the lowest.

However in the winter I struggle keeping 46, and usually I get 45 or so when I get angry, turn off the screen, and stop paying attention. I try to avoid using heat in the car, which helps the mpg I get. Though, most people wouldn't do that. My normal destination is a horse barn where I am outside 24/7, so the cold doesn't phase me anymore.

Its better than anything else though, so I can't complain.

 

I get 40-46 in the summer and 30-37 in winter. Sucks but it's the way it is. My Honda Odyssey only got 14 last tank. Gets 25 in the summer on the highway.

I do think the winter difference is more dramatic in the Prius than in other cars I've owned, though.

 

While's definitely worse than other cars, do remember that the drop in the Prius isn't quite as bad as it looks.

50 to 40mpg is 0.02gpm to 0.025gpm.
That's an extra 0.005gpm.

33.33 to ~28.57mpg is 0.03gpm to 0035gpm.

25 to 22.22mpg is 0.04gpm to 0.045gpm.

Mpg is deceptive.

 

You can say that again!

Traditional cars actually see a really big efficiency drop in SUMMER, consequently appearing to have less of a drop in the WINTER.

So, it totally how you look at it. Most just accepted that without question, since there were no other choices available in the past.

Overall though, it's the annual average that tells the real story. Prius shines when you see that big picture view.
.

 

Show me the data . . . . . and here it is:

 

I try to explain this to people all the time and it seems they just don't get it. All they see is a 10mpg drop and they freak out.

 

What I really care is the $ I spend, not data behind.

 

If all you were to read is your gas receipts you would sleep easier. The rest of us mpg freaks have to use sleep aids. LOL

 

Grille Blocking will help improve the MPG during cold weather. The foam in the grille helps keep the ICE warmer and at the optimal operating tempature.

Welcome to Priuschat! and hey! your in PA too!