Last post on May 17, 2013 at 10:15 AM
You are in the Toyota Prius
What is this discussion about?
Toyota Prius, Hybrid Cars, Fuel Efficiency (MPG), Sedan
#932 of 982 Re: mpg in 2011 model [hansjh]
Nov 04, 2011 (5:49 am)
The MPG estimate show on trip computers for most cars isn't as precise compared to manually calculating MPG (miles/gallons actually used). From what I've read, most are 5-10% inaccurate, so if your trip computer shows 53mpg and you calculate 50mpg that means the trip computer is 6% higher than your manual calculation, which isn't bad.
Instant MPG readouts can be very inaccurate, unless you're driving with the cruise control while on a flat road, since even slight variations in road or foot pressure on the gas pedal can greatly change an instant MPG. Remember MPG is Miles Per Gallon, so an instant MPG is looking at the MPG for one second and in one second at 60mph you've only driven .01667 miles, so when that .016667 mile is driven, only a tiny fraction of a gallon of gas is used. When that tiny fraction of gas is multiplied up to equal one gallon, any error is also multipled up. That's why in general estimating MPG is more accurate when calculated over greater distances...sort of like increasing the sample size in a survey to make it more accurate. You're wouldn't believe a survey if only one person was asked the questions, but you need hundreds or thousands of samples to get an accurate survey.
#933 of 982 Mileage dropped suddenly
Dec 03, 2011 (4:32 am)
My 2010 Prius is now giving me about 42 mpg in city. This used to be at least 45 in the summer with the AC on. I have changed my tires from the original goodyear assurance to michelin primacy mxv4. Is that the reason?
#934 of 982 Re: Mileage dropped suddenly [aghosh]
Dec 03, 2011 (6:04 am)
What are temperatures now? Also do gas stations in your area switch to an ethanol blend in the winter? Those one or two factors could by themselves explain what you are seeing on mpg. I know where I live, with temps now in the teens to 30s, I've seen my average mpg for urban driving (not in a Prius, but a Sentra CVT) drop from low 30s to upper 20s.
#935 of 982 Re: Mileage dropped suddenly [aghosh]
Dec 12, 2011 (10:55 am)
Our 2006 Prius goes from high 40s to low 40s MPG every winter due to the winter gas blend that in our area runs from Dec - April, as well as the colder temperature requiring longer engine run times to keep everything warmed up. You may notice that at stop lights, in the summer the engine may have been off but in the winter it may be running, especially if you're running the heater, since the heater needs hot water (hence hot engine).
Also, my Honda Fit's MPG also goes down in the winter, from the mid 30s to the low 30s, so this isn't unique with the Prius. I think that that Prius owners just track MPG more closely, so they notice the winter MPG drop more.
#936 of 982 Disappointed?
Dec 14, 2011 (2:45 pm)
I think reading too much forum raised my expectation too high. My first tank full of gas will get me 500 miles, mostly local 15 to 20 min communte. Display shows 48 mpg but if the full tank is 11.9 gallon, I will be getting 42 mpg. If dealer only filled up 11.5, then 43.5 mpg. Not too bad but not like what some report. Should I check tire pressure? Any suggestion to boost up mpg more?
#937 of 982 Re: Disappointed? [jsp9999]
Dec 15, 2011 (6:22 am)
Drive for 5 minutes to get the car warmed up and then reset the mpg button. See if that helps.
#938 of 982 Re: Disappointed? [jsp9999]
Dec 15, 2011 (10:16 am)
You need to fill it up and divide the miles by the gallons to get your MPG. For that 500 miles of driving you did, you probably only used a little over 10 gal of gas.
#939 of 982 Re: Disappointed? [bobw3]
Dec 15, 2011 (12:48 pm)
Guess I have to check what next tank will do. thx
#940 of 982 Re: Mileage dropped suddenly [bobw3]
Dec 15, 2011 (6:12 pm)
Thanks Backy and Bobw3. Bob, you are right on the money-the engine rarely shuts down at stoplights now, but earlier it seemed to shut down if I had to stop for more than like 10 seconds.
#941 of 982 my early experience with my pre-owned Yaris
Jan 10, 2012 (1:30 pm)
Just aquired my gorgeous 2010 Prius for $15,400 (has 45K on the oh-do). So far, after just 1/2 a tank, my car seems to be averaging only 47mpg according to Prius trip computer )which means I am probably getting just 45 mpg). I just placed more air in the tires and am learning from all of you how to goose more mpg from the beast. Janaury is a horrible time to set the bar for this car, so perhaps with warm weather and a few tankfuls I will see something over 50 mpg. The problem is my city commute is only 8 miles one way, and the car is barely warmed up by the time I get to work or to home. I have started to carefully track my gallons per fill-up and my odometer readings, so I should know in a month what my true MPG is going to be.
On the freeway I easily achieved a mpg over 50 mpg . . .which i find a little odd given the EPA estimates--but I realize athose estimates are based on paritial usage of the EV mode in the city, something that can't be accomplished on the freeway.
Anyway, I am a total computer/mileage geek, and so I am completely in love with the "geek-out" experience offered by the Prius computer readouts and such. It truly is an engineering marvel.
I dont think my tires are low rolling resistance tires . . .they are Westlake SP-06 . . .seem to be a softer tire made more for traction and/or quietness versus low RR. Seet this link and maybe you can comment on them? and recommend another tire? Is the "Michelin Energy Saver A/S" my best best?
Thanks so much.