Went from 53mpg to 44 one one tank.

Re: Wth, went from 53mpg to 44 one one tank.

You really should only see a couple MPG difference IMO. I know that the gas formulations are changing sometimes at this time of year and there is more Ethanol (upt o 10%) but that should not have made that much difference.

I have been reading some of your posts about mileage, and am not sure why you have such a spread in MPG's? Did you reset your TRIP B odometer at fillup and are watching from a reset??

Have you been taking any more short trips? Colder Temps?

 

Re: Wth, went from 53mpg to 44 one one tank.

Did your other tanks involve the same amount of rainy conditions? Rain and wind can kill your milage like no other!

 

Re: Wth, went from 53mpg to 44 one one tank.

I have lost about 4 mpg since the end of summer. Hard to see why you lost 9. You might start your tank over with costco gas and see what happens.

 

Re: Wth, went from 53mpg to 44 one one tank.

I have to agree my fuel mileage has dumped in the last two weeks. Temperatures are down twenty to twenty five degrees in the morning and it was been very rainy. Add to that I have a tank of E10 in the car and there is almost no way to win.

Last tank with temperatures higher by fifteen of more degrees and a tank of straight gas I averaged 53 mpg (HSI display). I'm lucky if I'm averaging 48.5 mpgs right now. It is so frustrating not to be able to raise my fuel mileage on my daily trips around town.

 

Re: Wth, went from 53mpg to 44 one one tank.

That alone could explain your problem. Rain can tank your milage because you are using energy to pump water from the tread in your tires. This is wasted energy and you pay for it with petrol.

If you had headwinds aw well you would suffer even more loses. Bad weather can be almost as bad as going up hills. lol

 

Sure. If the conditions are bad enough. I've dropped from 50mpg to 39mpg just having to drive through a major storm.

 

Just to double check, you did check you tire pressures right?

Rain really does make a difference. It has been wet here for about 4 days straight and I was down to 53 computed. Then after it dried up on Monday and even though it was cool (30s), I was able able to get 63.8 on a stretch I was normally getting around 57-58 on. I would agree the rain and wind seem to have a greater impact than cold. But it hasn't gotten really cold here yet. More on that later.

 

Absolutely! I agree with F8L and others. I would bet my farm (if I had one) that the gas brand has nothing or little to do with your MPG drop. Rain and colder temperatures are the perfect combination for a MPG drop, second only to speed.

It's too early to come to any conclusions, but based on my weekly 350-mile travels, if you drop your cruising speed from 75 MPH to 65MPH you can get an improvment of 8-12 on your MPG in the same conditions. Amazing!

 

It seems obvious to me that it is a combination of things each costing an MPG or two.

Cooler temps
Rain
Defroster
Winter fuel
*****
The prefect storm.


The Prius is like a category 5 hurricane. A CAT 5 HURRICANE requires an almost perfect set of environmental conditions to maintain that strength. Any change in those conditions will rapidly weaken the storm. A category 1 or 2 storm can survive all kinds of wind shear, cooler water, limited land crossing and still maintain much of its original strength.

So yes, the things listed significantly effect the mileage of the Prius and much more than an average car. But that's because the Prius, like the Cat 5 hurricane, operates at a much higher level of efficiency to begin with.

 

Although weather definitely does have an influence, it could have been bad gas. With a previous car (I don't remember whether it was my 2006 Prius or the Infiniti I had before that -- I think it was the Infiniti) I had filled up with Citgo at a 7-11. The next day, it wouldn't start! I had to call AAA to get it started, and he speculated that it was bad gas. Needless to say, I never returned to that gas station.

A couple of weeks ago, I need to get gas and I filled up at a gas station -- it was a brand name, Chevron, I think -- that was the most convenient to get to at the time, but the station seemed a little run down. I saw my gas mileage drop immediately. There might have been other factors, such as hills, red lights, and so on. But I think the gas did have an effect.

I usually look for a station that looks clean and well maintained. There might be some differences between brands, but probably not.

 

Almost certainly the colder weather. Don't hyperventilate over this. The results of one tank mean very little.

 

I noticed a 3-5 MPG drop in mileage since the the beginning of the month. Oregon is a all year 10% Ethanol gas state. The winter formula gasoline has even a lower BTU per gallon. I sure miss the old days with regular gasoline.

alfon

 

This is a most interesting thread, and very thought provoking.

I too have detected a small decrease in my mileage the last two tanks. My routine is not as regimented as those that drive the same distance each day, but I can see the impact. For many years (long before I bought a Prius) I closely monitored my mileage .... I concluded that you take a tremendous "hit" with Winter blend fuel . Speed, however, is probably a larger factor; rain certainly does create more drag as well. I spend one full day in Yellowstone NP where the speed limit is 45 mph. I drove a steady 35-45 mph all day (with frequent stops). I filled up that morniing and again that evening. The calculated mileage was 65.7 mpg. The Prius is capable of delivering tremendous efficiency, but few can drive within the limitations. The EPA figure is a good guideline for normal driving, but external weather and geography .... and traffic, certainly do impact the fuel efficiency. BUT, these same factors impact all other cars on the road. Find some comfort that even though your Pries is down a bit ... so are all the other cars.