Hi guys, I recently got a used 2010 Prius with 63,000 miles on it. I put new tires on it (Michelin Pilot Sport A/S 3 on the 17" wheels) and since driving 1,589 miles I've only seen 38.6 mpg (calculated directly from miles driven divided by fuel purchased) I'm down in South Carolina, so while it's cooler, I've still been driving in the 50-65°F range. About 80% of the miles are highway, and I'm driving much more fuel-consciously than I did in my old 2004 (172,000 miles averaging 39.7 mpg over the last 70,000 miles I had it), even going so far as to drive only in Eco mode. Is it the Michelin tires? Also, I noticed the guy I got this from had 5w30 oil put in it—could that do it? Any other ideas? I thought the Gen IIIs got better mileage than the Gen IIs.
17" tires make a big diffrence, check tire pressure run may be 40 front - 38 rear or higher check side wall on tires do not go over max PSI, with 17's you might be able to go up to 50 front - 48 rear or higher. May ride rough at higher PSI. Oil makes a big difference check your manual what does it say 0-20w? check, do not over fill. Speed kills MPG. I run 62-67 on interstates if possible, I know not always can be done, drive safe.
The recommended oil for the 2010's was 0W-20. You have to wonder why the previous owner used 5W-20 instead of the recommended weight. That would account for a small decrease in MPG. Like stated above, the 17's will have a bigger effect on your mileage.
My old 2005 averaged 45.6 mpg for 7 years 15" wheels 40 psi front 38 psi rear. With a 2010 You should be up in the 46mpg and up. If you are driving 70 mph or faster on interstates, with 17" wheels and have lower psi such as 35 front and 33 rear, and the wrong oil, yes 39 mpg is very likely even lower.
Michelin Pilot Sport A/S 3is a high performance tire and not LRR. You lose 4-5 mpg with this tire right out of the bat. Plus 17" and 5W20 oil, you lose another 4-5 mpg.
How fast are you driving on the highway? Are there many hills where you usually drive? Averaging under 40MPG in a Prius is just unthinkable to me.
On the interstate I drive 70+ (since for my common drives the speed limit is 70 mph). I know, of course, that going faster leads to poorer fuel economy, but I'm driving more carefully than in my 2004 Prius with 172,000 miles (on the exact same drives) and getting worse economy, which seems a bit crazy... Perhaps it's "death by a thousand paper cuts"—larger wheels, performance tires, tire pressure, 5w oil, etc.
Have you read much about getting good mileage in the Prius? Even at 70MPH, you should be getting better than 40MPG, there may be some things you do that you think are good for mileage but end up hurting it. How much air in the tires? Why such good tires? I put Michelin Pilot Sport A/S's on the back of the '04 GTO I owned and they stuck like glue with 350HP going through them.
It's got to be your tires and wrong oil. Switch to LRR tires, change the oil and you should see improvement.
Also check into grill blocking; under Accessories and Modifications . And you need 0-w-20 oil in your 2010 Prius !!
I went with the A/S 3s for 2 reasons: 1. Price: I paid $116/tire mounted and balanced (lifetime rotation, etc.)! I have no idea how they ended up being so cheap; I will say I bought them at a Goodyear store near my house (I went there to price the Fuel Assurance Max, which was $152.50/tire!). The cheapest (at the time) I could find the Michelin Primacy MXM4 (I think that was OE, right?) was right at $200/tire. So I saved $336 over going with the OEM tire, which should offset the 3-4mpg loss, I think. 2. Quality: While I take Consumer Reports ratings with a grain of salt (their electronics ratings are laughably outdated, typically), I do value their tire ratings. The Pilot Sport A/S 3 is CR's highest rated tire that can fit my wheel. It also features the same treadwear rating as the Primacy MXM4 (UTQG = 500AAA), so it should last for a similar amount of time. Anyway, my point is this: I was about to spend more money for a noisier, [arguably] less safe set of tires to maintain fuel economy. Once I took a step back and thought about it, the difference in price covers the predicted loss in fuel economy (I was thinking it'd be about 3 mpg, which means @ 45,000 miles I'd use about 70 gallons more gas, assuming a drop from 45 to 42 mpg. With gas here around $3.10, that's $220; $303 if 4 mpg loss).
Both our 2003 and 2010 Prius are getting 52 MPG, year round. But the 2010 does it about 5 mph faster and handles warm-up better. My usual commute is long enough both cars achieve hybrid operating modes well before the commute is over. Bob Wilson
