Went from 53mpg to 44 one one tank.

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

Tideland, how did you block the grille on your 2010?

It seems to be time to do it, and I don't want to start a new thread on best ways to block the grille on the 2010 without asking you first if that has already been discussed.

 

I am wondering just how much things like cooler temps, rain, using the defroster, etc. will affect my mileage. We got our Prius on Sep 11th and enjoyed a month or so of nice weather, during which time the mileage was 50 - 53. Since then it has dropped to 44 - 47 and about the only difference is cooler, wetter weather with the defroster running a lot (I live north of Seattle and the climate tends to be damp.)

44 mpg is not bad but I agree with Gasitman that it has been a surprise to see it drop so much so fast.

 

Here in northwest Oregon we noticed a similar drop in MPG. The last trip was over 57 MPG calculated back in September during nice weather. Now we are averaging in the mid 40's for MPG's.

Rain soaked roads, cooler temps, wind, and winterized gasoline all help lower MPG's.

Even though the official EPA is 50 MPG for the Prius there is no way you can possible obtain that driving here in Oregon during this time of year with all the variables.

alfon

 

In Seattle WA, I also noticed the recent drop in MPG from 52 to 49. Same as Alfon, the weather here is wet in winter months. I would say the temperature in Seattle in mild in winder about 40-50 F most of the time. Even so I still see the drop of 3 miles per gallon.

 

Keep in mind that with larger numbers you will see a larger numeric decrease in MPG than you would if you started with very low numbers. The overall net effect will not, however, translate into a large difference in gallons used (in the Prius) when compared to a conventional low MPG vehicle.

I.E. a 10% drop in fuel economy at 50mpg would put you at 45mpg and a loss of 5mpg. A 10% drop at 15mpg would put you at 13.5mpg and a loss of 1.5mpg.

So while the Prius looks like it is taking an abnormally large hit in MPG it really is not if you assume that the low MPG vehicle is taking the same 10% hit due to weather.

Cost difference between non-efficient vs. efficient vehicle over a year and assuming a 10% decrease in efficiency due to weather.

15mpg to 13.5mpg = $277/yr

50mpg to 45mpg = $83/yr

*This is based on 15,000 mile annual miles driven and $2.50/ga of gasoline.

 

I had something similar happen to me using Citgo gas. Filled up with another brand and mileage went back to normal. Don't really think it was the brand thing though, just bad gas.

 

The off brands of gas are not as good, sometimes. Sometimes you get what you pay for.
Top Tier Gasoline
If you don't believe this, then why did the top auto manufacturers create it?

 

On a previous car (I don't think it was my 2006 Prius -- probably my 1996 Infiniti) I filled up with Citgo at a 7-11. The next day my car wouldn't start! I called AAA and they guy that came out to start my car said it was probably bad gas!

Now, I always make sure the station looks clean and well maintained. I think that is probably more important than the brand, per se. For example, I've gone to Raceway and Sheetz when I'm on the road (there aren't any of those in my area), and haven't had a problem .... they generally seem very clean.

 

Don't know where you live in Washington but Seattle/Tacoma has had ethanol at all the major name brand stations for several years.

 

The biggest hit seems to come with cold weather. A head wind is a real mileage killer, but a tail wind helps. Going through the Colombia River Gorge between where I live and the Willamette Valley there is frequently wind from the West (even when the legislature is not in session). The elevation change is minimal for the trip but due to wind I sometimes see a 6 to 8 MPG difference. Last trip 43 to 44 MPG for the 200 miles going West and over 52 MPG coming back.

If I maintain the same speed I also see a pretty good jump in mileage when I fill up with E0 in Idaho or Nevada vice the E10 junk we are forced to use here and in Washington.

I have not noticed a difference between gasoline brands. I took a 3500 mile trip earlier this fall and bought gas from Citgo and cut rate stations as well as the Shell and Standard I usually use. There was no discernible difference in mileage or performance. I do try to buy gas from stations that look well maintained and do a lot of business. I am told the gasoline all comes from the same refineries anyway and only the additave package is different.

 

The winter weather here is really making MPG's drop like a fat rock.

The last fill up was 43 MPG, lowest ever.

Also we have over 14,000 miles on our Prius. I purchased tires 4,000 miles ago, MichelinEnergy Saver AS, 195X65X15, and have 44PSI of Nitrogen in all four tires.

Oil is Mobil 1 0X20 synthetic with 4 quarts in the crank case, not 4.4 as listed. So it is not over filled but at around the3/4 mark on the dip stick.

So, everthing is set up for max MPG's, the best oil, the best tires, and enough miles to say it is fairly well broken in.

I just never in my life seen a discrepancy like this.

My 2003 Jetta TDI(diesel) Wagon 5-speed, only takes a 2-3 MPG hit in the winter and has an overall average of 52-53 MPG.

My only conclusion is that the gasoline here in Oregon is formulated to the extreme with Ethanol, and maybe the winter formula is 20% instead of the 10% required by the State of Oregon.

I notice the distinct sweet smell of Ethanol when the gas is getting pumped in. Also when a car goes by me in the parking lot I can smell the sweet smell of Ethanol from the exhaust.

That to me is a good indication of maybe too much Ethanol in winter gas which at a 20% level would contribute to a big loss in MPG's.

Also I buy my gas at Costco in Warrenton Oregon. Which during a September road trip we got over 57 MPG with gas bought at the same Warrenton Costco.

alfon

 

Re: Rain, Rain - RAIN

I do have the Prius V which has the wider tires (more water to push), but rain causes a huge drop in mileage. On a long highway trip with substantial rain I got 40 MPG. I didn't even think that kind of MPG was possible with the Prius III. Same trip coming home got around 50. Rain just takes a big hit on your mileage (not drizzle, I am talking rain). A lot of water weight to push aside, along with less traction in general, just eats away at the mileage. Really surprising actually, just how big a hit it causes.

 

I went from about 54-55 mpg to now in November about 49 mpg.

 

This week I took another member's advice and lowered my heater temp from 74 to 68 and the MPG has gone up by 3 MPG based on the computer readout. Very worthwhile.