When we bought our Prius, the temps were about what they are now; 40-50 daytime. From the start, we were getting 52-54mpg for local driving (city-short trips) and 58 on the highway for long trips. For the last two tanks of gas, the mileage has dropped to 35-38 for local driving and only gets up to 50 on long trips. Driving style hasn't changed and I checked the air pressure. Any clues? My husband thinks the car is running a bit rough but I don't hear it. There are about 7700 miles on the car now. We are 180 miles from the dealership (one that I trust) so hoping it is something simple.
We don't know your geographical location, but suspect it is several factors: 1) new Prius owners-drivers 2) onset of cooler autumn-winter weather 3) Prius is not yet "broken in" with more than 10k mi (16k km) Fuel economy always takes a drop with cooler-colder ambient air temperatures.
Also winter gas formulations in some areas can cause a drop in MPG. Around here that happens in October both last year and again this year I noticed a drop of 4-5 mpg from one tank to the next at this time of year.
Wow, 4-5 mpg drop just with different mixture. It's been hard enough getting over 50 and now I may have to try just as hard to get in the high 40s? Oh brother.
I noticed a significant drop in the mpg this last tank. I am certain it is the winter gas as everything else has stayed pretty much equal. I took a good 5 mpg hit.
I too have noticed a significant drop since we've been in these cooler temps. I've also noticed I take a big hit (more than usual) during my first 5 minutes of driving. I was interested to see some threads about block heaters and radiator coverings to minimize the warm-up time at engine start. I ordered a block heater. We'll see. . .
Every time someone mentions dropping mileage in the winter, I point them to my lifetime mileage chart to show that they are not alone. Click the link in my signature.
I would have thought of the temps changing BUT it is now the same temps as when we bought it in early March before they would have switched to summer gas formulations. Any possibilities that the formulations are now drastically different due to the Katrina, etc.? Driving methods just don't change which is why I got the much appreciated mpg before. I am going to have to check the mpg in my other vehicle and see if it has changed too. We are in NW MI
When I changed my first oil fill it looked much thinner than my 5W-30. I think that made my mpg drop a bit when I lost the break in oil. Beyond that slight temperature differences have a big effect and not just the current temp when you start out in the morning. Battery temp will depend more on the min temp overnight. Till it gets warm the engine races more and burns more fuel.
The good thing about the Prius is that it gets such good mileage. The bad thing about the Prius is that any little change in weather, road conditions, type of gas, or length of the trip has a greater adverse effect on the mileage than any other car. Ours has about 7800 miles on it and the ave. has been 45-48 mpg. When it's hot, the air conditioner lowers the mpg. When it's cold, the engine warmup lowers the mpg. When we get winter gas, the mpg goes down. When we installed better tires that wouldn't slip on wetr roads, we lost about 1 or 2 mpg. As near as I can tell, here in central WI, we have a small window of time in April/May & Sept/Oct when neither the heater or air conditioner are needed and summer gas is available that I can expect better mileage. With all of that said, the Prius is still the most efficient mid sized car available today. Because of the premium we have to pay to get the Prius (compared to other midsized non-hybred cars) I don't know which choice offers the best overall value, but it doesn't really matter though, because we have it now and in another year we'll probably have something else. Doug
Most people quote the numbers they see on the sticker when they bought the car. They do not keep records. If you feel you can challenge them, they might start keeping records and learn. Almost no one I meet knows about the decreased milage with the seasons, decrease temps, changes in the formulation of gasoline.
Anybody thought of using the trick the Insight drivers use of putting in an air-dam infront of the radiator - blocking some of the air from passing over the radiator - so the engine stays warmer in the winter? Then, your MPG stays higher. It just hit near 80Fs here in Socal today and my MPG was back to high 40s (47-53s) again, when it was dropping to near ~45 last week when it was closer to 59F so it brough back this memory.
With no temprature gage how would you know if it were getting to hot. I guess the warning light would come on eventually but I would be reluctant to try it.
My last tank showed a 4 mpg drop and guess what I found, my right rear tire had a slow leak and it had dropped to 17psi. Fixed it, and now I am back to where I was. DON'T overlook the Obvious!!!
Yes, I've blocked mine and several others have (look at the block heater install thread in the Performance Mod forum). Initially I blocked the whole thing and on the cool day after I did it everything was fine. I monitored the ICE temp with my Dyno-Scan and it stayed in the high 170s range. The next day the tempertures went up and my trips were a little longer and my ICE temp would creep in to the 190s and I got a bit nervous. I've now uncovered about 1/4 of the radiator and with temps in the mid-60s haven't seen it get over 187 degrees. But I agree, either only partially cover it (maybe 1/2) if you can't monitor temps or monitor them closely if you can.
The Prius drive compartment is so tightly closed that very little uncontrolled air flows through it. Prius knows what engine temp it wants at any given operating condition and works to maintain that; interfering with its control mechanisms by blocking the radiator is not likely to help and may hurt.
While you may be right, as long as I have the ability to monitor critical factors such as Engine temp and only use it in the cold weather I think harm is negligible. If, indeed, there is no benefit then I probably won't bother next winter. However, there is unquestinably air flow through the engine compartment that can act to cool the ICE and/or delay heating. Those in the coldest weather areas have reported successfully blocking the radiotor with improvement in performance. I've also added insulation to the hood area and the engine block heater and am hoping to see significant winter performance this year. I have 2 prior winters for comparison. I don't think it will be easy to sort out exactly which of my 'winterization' techniques made the biggest impact, but I suspect the engine block heater will be the biggest thing. Again, however, your words of caution should be heeded and I don't recommend covering much if any of the radiator except in very cold weather if one doesn't have a means of watching the ICE temp.
