markwill12

I got my ES300h around July. On my first commutes I was playing the MPG game and getting awesome mileage. I remember my first trip to work I achieved 46 MPG Over time I became a little less worried about the MPG and just drove "normally". But I was still getting just shy of 39 MPG for the same commute.

Over the last few months I have noticed my MPG falling. Obviously there are a number of variables to this but it seems unmistakable that the MPG is getting worse. A couple of months ago I was getting 37 or so, then it became difficult to get 35 and so on. Now, my commute is getting about 32 or so. I am a very lightfooted driver and my commute is, for the most part, very flat (it has a 1 mile hill at the end).

Obviously the actual journey is the same. I do it at the same time of the day and so generally the stop/go aspect is the same. The weather is a bit colder but not the extent I'd expect to see that big a jump (we are still at the point where it's above freezing for example).

Does that raise any red flags? Each passing week it seems like my average is falling.

Mark

lesz

If your temperatures are in the 30s or even the low 40s, that is enough to cost you a few miles per gallon compared to what you would see if temperatures were in the 60s or 70s. That will be even more true if you are doing a lot of short trips and parking the car long enough for the engine to cool down. The biggest factor causing lower mpg in colder temperatures is during the time it takes for the engine to warm up to its normal operating temperature. Thus, the more often the engine needs to warm up, the bigger will be the effect on mpg.

Also, I've found that vehicles that I've had with V8 engines see the smallest drop in mpg when it is cold. Six cylinder engines are worse, and 4 cylinder engines are even worse. Thus, when the gas engine on the ES300h is being used, it wouldn't surprise me if the drop in mpg was greater than the corresponding drop in the ES350.

Arty101

I think most hybrids experience a fair drop in FE during the winter months due to weather and other factors. It could also be a change in the gas formula from summer to winter blend, which they do in Calif. They may also add more ethanol (thank the corn lobbyist) , which is less fuel efficient.

ElliotB

Are you using your heater?

lesz

Using the heater should have virtually no effect at all on mpg. The heater is just using heat that the engine would have been producing anyway and diverting it to warm the air that the climate control system is sending into the passenger compartment. Using the seat heaters and heated steering wheel should have a bit more effect on mpg, but, still, the impact of using the seat heaters and heated steering wheel should be relatively small.

ElliotB

Lesz, you would think that is the case but it actually does.

lesz

You are going to need to explain that more because, other than the minimal power that is used to divert the engine heat and the fan, no other power is being used to produce the heat or get the heat into the passenger compartment. Tell me what I'm missing.

DaveGS4

iTrader: (2)

The gas blend that is sold changes in wintertime which can impact performance and MPG

http://www.popularmechanics.com/cars...rence-13747431
http://auto.howstuffworks.com/fuel-e...mmer-fuel1.htm
http://www.bellperformance.com/blog/...Blend-Gasoline

ElliotB

I have been driving hybrids for over 7 years and have always found that colder weather (cold enough to require using the heater) robs you of MPGs.

There are several reasons why FE drops when it gets colder. But the main one I believe is that the engine has to run more to keep it hot so you can get heat in the cabin. Warm up takes a lot longer as well, so the gas engine runs a lot longer until you get up to operating temperature. And has to run more to keep the engine at its most efficient operating temperature and provide sufficient heat to the cabin.

Additionally, you are using your lights, seat heaters, possibly rear defroster and blower fan more which use energy as well.

Cerulean99

Lesz, I tried to play around with the heater and it definitely causes the gas engine to stay on at times. I would be at a stop and expect the engine to shut off, but it stays on. As soon as I turn off the heater, it shuts off and the EV light goes on. So using the heater definitely uses more gas. I'm not saying that the engine stays on all the time the heater is on, but I noticed it does in some cases.

jollick

The hybrid batteries, as all batteries, are not as efficient in the colder temperatures so this is another factor, as are the ones mentioned above. I have seen a drop of 1 or so mpg in the last month. However, getting 36.5 mpg out of a car like the ES with normal driving is fantastic.

lesz

I see what you are saying, and, if that is the case, hybrid mpg would be affected more than would non-hybrid mpg. With my ES350, if I watch the fuel economy monitor while driving at a steady speed and turn the heater on and off, doing so has absolutely no effect at all on mpg.

While I would concede that use of the heater could affect mpg with a hybrid, I'm still confident that the major cause of lower mpg with any vehicle, hybrid or non-hybrid, in cold weather is the increased amount of time that it takes the engine to warm up to normal operating temperature. With my ES350 and very little of my driving being done in stop-and-go conditions, my typical mpg during the summer was around 34 mpg. As temperatures here have dropped into the 20 degree range, my mpg has dropped to about 31 mpg. However, if I'm driving 30-40 mile trips, I will still get close to the same mpg as I was getting during the summer. The bigger drop in mpg happens when I'm doing lots of 5 mile drives (or less), and the engine has to warm up repeatedly after each shutdown.

alpinefun

Lesz,
That 34 mpg for ES350 is very impressive! I guess it's mostly highway miles.

lesz

I live out in the country. Most of my driving is on country roads with minimal need to stop or idle. Another factor is that most of my driving trips are 20 miles or longer. Since a major drop in mpg occurs during the time when the engine is warming up to normal operating temperatures, my mpg is a lot better than it would be if I were driving mostly short trips and having to rewarm the engine every time I started it up again. Also, my driving style has become much more conservative than it would have been a couple of decades ago. That said, I'm sure that my mpg would be even higher, but the area where I live has lots of steep hills, and they cause a significant hit to mpg.

Arty101

I was thinking the same as Alpine. Boy with FE as high as 34 mpg, who needs a hybrid 300h? Nice to be able to drive flat, straight and with no traffic.