Absolutely dismal MPG...

[SW03ES]

We drove the Prius today in the snow (its better in the snow than the Lexus) and I noticed how terrible the MPG had become...get this...26.6. Thats got to be some of the worst mileage I've ever seen reported on here.

Any ideas? Its cold but its not that cold. My fiance drives a very short commute to work but still....

[TheForce]

Was there a lot of slow stop and go driving with the heat on? This will cause the mpg to drop. I remember last year we had a quick snow fall and I was stuck in traffic for about 2 hours. dropped my mpg from about 55 to 45. But I also did not have the heat on or anything.

[Stev0]

OK, everybody in unison, on the count of three!

1-2-3:

COLD WEATHER PLUS SHORT TRIPS = BAD MPG.

Anything below 35 can be considered cold.

[Bob64]

winter actually gets ya in 4 ways:

winter gas
heater = on (unless your wearing layers)
stuck in stage 3/3a (unless its a long trip)
lower tire psi


Anyway, first, winter gas has less energy, so the car has to use more of it to do the same work.

turning on the heater robs the valuable heat from the engine, forcing it to drop out of stage 4 (if you manage to get into stage 4) when the coolant temps drops below.... 70C or so. Believe me when I say the heater makes it drop FAST. A minute and it'll drop it from 80 to 68C... depending on how high you turn up the heat of course...

stuck in stage 3/3a, due to the cold temps, the coolant does not reach 70C easily. In addition to the heater being on, you may remain stuck in stage 3 for the majority of your trip. (symptoms of stage 3: engine on at speeds below 35mph unless stopped)

and finally, cold air reduces air pressure inside your tires... thus you need more of it to maintain a high tire pressure. (low tire pressure increases rolling resistance)

And for the record, depending on the traffic, a good hypermiling run for me in traffic will yield about 55mpg in the wintertime as opposed to my record of 75mpg during the summer time. However, a bad trip (huge congestion, traffic, barely crawling along) for me will be about 40mpg.

If you find yourself in really bad traffic, I suggest the following:
Avoid turning on the headlights (unless it is snowing or is dark)
turn off the audio/radio/cdplayer
turn off or reduce the mfd brightness
turn off the sks
avoid turning on the heater except to defrost the windows.
Try to get into stage 4 mode. (stop for like 6 seconds if the engine is on, and hopefully it is 70C or higher and will then enter stage 4...)

The point of these measures is to conserve the hybrid battery as well as to avoid the engine turning on to remain warm.
I will also recommend blocking your grill (at your own risk!) in these conditions.

[Tideland Prius]

Dunno but it snowed over the weekend and crawling along with traffic (cause we're not used to the snow), I got my worst mileage ever on the MFD - 8.0L/100km (that's 29mpg!!)

[galaxee]

you don't wanna know what my hellacious commute alone gets me... add in cold and heater and winter gas up there by you and that's a big hit.

what kinda commute are we talking here? and did you just fill up or reset the mfd before the trip?

[Schnauzermom]

Originally Posted by Bob64

winter actually gets ya in 4 ways:

winter gas
heater = on (unless your wearing layers)
stuck in stage 3/3a (unless its a long trip)
lower tire psi

But you'll know if your tire psi is low, because you'll have that bright red symbol aglow on the dash.
Mine scared the crap out of me the first night I was out late and the temp dropped. Yeah, they were all a tiny bit low - by no means anywhere near flat.

I'm just not used to warning lights for potential problems or routine maintenance. In my Prism, lights were "idiot lights" that only came on if there was a huge problem, like the death of the catalytic converter, or the time Firestone failed to tighten the oil plug after changing the oil and I wound up over 2 quarts low.

[Tideland Prius]

SW has an 04 so it doesn't have a TPMS.

[Boo]

Originally Posted by Schnauzermom

But you'll know if your tire psi is low, because you'll have that bright red symbol aglow on the dash.
Mine scared the crap out of me the first night I was out late and the temp dropped. Yeah, they were all a tiny bit low - by no means anywhere near flat.

I'm just not used to warning lights for potential problems or routine maintenance. In my Prism, lights were "idiot lights" that only came on if there was a huge problem, like the death of the catalytic converter, or the time Firestone failed to tighten the oil plug after changing the oil and I wound up over 2 quarts low.

It's the Tire Pressure Monitoring System. It's a major safety feature. Underinflation is dangerous. The TPMS alerts you when the pressure of any tire drops 25% below its registered setting.

[SW03ES]

Yep, '04 no TPMS.

I'd agree with you if this were just an isolated occurance, but we've been getting bad mileage for a while now. 26.6 is a new low (the tank has about 50 miles on it) but we've regularly seen it at 29. I don't think we saw 40 at all this summer. We used to get much better mileage.

Its a pretty short commute, maybe 3 miles. Even when it gets driven more normally though the mileage is not as good as it used to be.

The tires are good Michelin MXV4s aired properly, I check tire pressure weekly.