Question about MPG

The car has a built-in mileage computer. According to that computer, I averaged 51-52 MPG from last September through the end of May of this year. Mileage dropped to about 48 in June and 46 in July, but it's now back up to 51.

I live in the Phoenix area, and temperatures were 110+ most of June and July. Now they're in the high 90s or low 100s.

My driving is a mixture of metropolitan-area freeway and suburban/rural. I use cruise control wherever possible and try to keep it set at 65 on the freeways.

The Prius in the US has a bladder inside the gas tank, so fillups are not consistent because of bladder elasticity changing with temperatures.

Also keep in mind that a ten percent variance from 55 MPG (EPA average MPG for the Prius) is 5.5 MPG, whereas a ten percent variance from 20 MPG is only 2 MPG. When comparing variances from the EPA rating use percentages, not absolute numbers of miles per gallon.

How do you expect anyone to email directly to snipped-for-privacy@nospam.org?

Who is me? I missed your name. And your e-mail address is snipped-for-privacy@nospam.org? There are ways of posting your e-mail address so that it is not machine readable...

Davoud

M.S. I do not understand how your Prius can get such good of mileage. I'm in the same hot environment in the So. Cal Central Valley and I'm only getting

38 mpg now with AC running almost always. Very odd, although the local dealer has no explanation as to why a couple of Pri's in a company pool vary so widely in their mpg's. Even though the drivers rotate between them, they still produce the same mpg for the most part (one at 37 and the other at 46). Must be good ones and bad ones?

Best I did was 51 mpg in San Francisco, but that area didn't require AC. Fwiw, my AC does work pretty darn well and cools down within two minutes or so. Maybe the compressor drag accounts for some of the differences?

Running I-5 the way I do (85+) can get it down into the upper 20's to lower

30's. Also, our gas is pretty watered down during the summer months with the "blend." Don't know if Arizona has accepted the watered-down ethanol stuff yet?

B~

I can tell a Prius isn't in your future. Buy something else which already has a bad reputation that can't suffer from more negativity. mark_

I don't understand why people wonder why they are getting low MPG when they continually drive on the interstates at high speeds while running the A/C. The Prius is very capable of achieving over 60 MPG once you realize it's not a sports car.

I suspect there are some Prius that have undiagnosed problems that drop fuel economy into the 30s. We used to see a lot more of those reports in the Yahoo Prius forum, but they have become less common for some reason.

Assuming your tire pressures are okay (the stock pressures will cost you about 5 mpg and wear the tires rapidly in the first generation - not sure about the current version), there are a couple things that have been known to cause such poor mileage. The first one is easy enough: some shops overtension the parking brake cable and the parking brakes drag. If you use the parking brakes regularly that goes away in a week or two, but applying the parking brake hard and releasing it about ten times apparently does the same trick. The other one was only reported once: the fuel injectors tested bad and were replaced under warranty. Problem solved.

Mike (getting about 50 mpg in Flagstaff until we changed tires, now mid-40s)

I don't know why you're getting such low mileage. As I said, I tend to keep at 65 on the freeway; most of the rural driving is at 45 to 50, and in the city it's 25-35. The lowest I've ever had was 42 MPG, and that was on my first tank.

I make heavy use of the cruise control whenever I can, and the rest of the time, I keep a light foot on the go-pedal, and try pulse-and-glide whenever I'm able if I can't use the cruise control.

I know people who routinely get the high 50s or even low 60s; I don't know how they do it.

We get MTBE in the Winter and ethanol in the Summer.

What tires did you get? I want to avoid them when I have to change tires.

You'll notice most of the complaints come from those who are part of the high speed congestion. So, my guess is the complaints are merely indirect complaints. If one is all alone on the highway and still insists on traveling 85 miles and hour and bemoans the Prius mpg's then as far as I'm concerned they are just out of touch. Or, the complaints are really meant to impress as if none of us ever dared to drive so fast, or can't afford to run the AC.

As you have found, the EPA tests no longer accurately reflect most American's real-world driving. The tests were set up in the 1970s (with a minor mathematical correction applied in the 1980s), and the vehicles do not use heat or AC, run at 68-86^F, and never go faster than 60MPH.

However, the same tests are applied to all vehicles, so it is still your best choice to compare one vehicle against another. If you know what your real-world fuel economy is with another vehicle, use that model year and trim level's MPG from andfind the % difference from the EPA MPG to your own MPG. Then apply thesame % difference to the EPA MPG of the vehicle that you're looking atto get what you may expect in your own real-world driving. (Everyone's"real world" driving is different...) Other sources of Prius information:

I got Yokohamas. In fairness, I haven't bothered to see what pressure I can run them at; if I can do 42/40 they should be better. However, they are 195s and not LRR so there may be limits....

Mike

My Prius got into a mode a while back (last summer) where it wouldn't charge the battery and the engine ran continuously. Problem went away with a re-start and then reappeared a few days later. It was hot when it happened and the A/C had pulled the battery down. Hasn't happened since the last recall upgrade but I have no reason to believe that upgrade solved the problem. Read about an identical situation in the Prius_2G group a few days ago.

snipped-for-privacy@nospam.org wrote:

We have had our Prius for nearly 3 months and have been driving it mostly around town and short trips in Boise, ID. Temperatures started in the 70s when we got it, but were in the high 90's to 110 through the month of July. We use the AC constantly. The first tank, we got 48+ mpg, but it steadily declined with the hotter weather, to where we got a little over 45 mpg on the last tank in town (with high temperatures over 100 every day). Then, we took a trip from Boise to Newport, OR, from which we just returned today. I avoided the freeeway, driving over on US26 and back on US20 (they are the same highway for a ways at both ends, but 26 takes a more northern and mountainous route across central OR, whil 20 takes a faster but ugly, desert route). I stuck to the speed limit (55 almost all the way, with a bit of 65 in Idaho) and used the AC the entire trip with the exception of the time on the OR coast. On the way over (the mountainous route), we got just over 54 mpg. On the way back (flatter route), we got 55.7 mpg - and that was with a net increase in altitude of 2800 feet from Newport to Boise. Most all the trip, I used the cruise control set to exactly 55. Where the speed limit was 65, I typically went about 62. I could improve my mileage by not going so fast up the hills, but my wife gets nervous when the big rigs start pushing us... Net economy for the trip (over 1300 miles) was 53.3 mpg, but that includes 250 miles of short trips in Newport and up and down the Oregon coast, where we were getting under 50 mpg.

You realized a net economy of 53.3 mpg. Good for you. It's the overall that counts. I find it interesting your mileage is much better than mine was in the same area but it's explainable. Had I stayed longer the car would have adjusted. If you want to see eye popping mpg's come out to New England where most of the major highways, on average, are not too much above sea level. I live in Agawam, MA.. My home is about 200 feet above sea level but most of the town is barely above 60 feet. Denser air, better performance. You'll probably see high 80's (LOL) until your computer catches on and makes changes. mark_

Was it uncomfortably hot in the cabin when this happened? The traction battery and its electronics draw their cooling air from the cabin. Continuous A/C use can cut MPGs 10%, but it is necessary in hot weather to keep the battery system working properly.

I don't remember. Is it possible the A/C can draw from the battery at the same rate the engine can charge it? Hasn't happened this summer and I've driven several day with temps in the high 90's and one 65 mile trip in the low 100's.

I've been driving my Prius for about 3,100 miles, mostly around town, short trips of no more than 15-20 minutes, usually under 65mph. I pulse & glide when possible, but that's a very small percentage. Here in Augusta GA, it's been 90-106 degrees, and I use the A/C all the time. Only rarely do I use Cruise (one 1,000-mile trip @85mph, one 500-mile trip at 75mph). My tires are stock and at 42/40.

My best mileage for 100 miles or so has been about 49mpg, but I generally average right at 45-46. Always between 43.5 & 46.2. BTW, I use the MFD as I've found that hand calculation isn't as accurate for tank-by-tank calculations. See the "Who do you believe" thread for more, or visit greenhybrid.com.

Have you seen the Prius FAQ in GreenHybrid.com?

What model year?

Bob Wilson

Yes, Bob, I'm Uwaku, driver of "Smudge," an '06 HF3. Thanks!