Reduced mpg in 2008 Prius

Was the mpg drop before or after new tires? What tire did you get?

 

Try cleaning the Mass Air Flow sensor under the air filter. Special cleaner for it. Or have the dealer do it (it can be damaged with the wrong cleaner). If your air filter was changed regularly probably not it. Try a tank of higher octane. I used fuel injector cleaner in the gas which reduced my mpg for 2 tanks but after that increased mpg (strange). My AC on/off only makes a difference of 2-3 mpg. Run the diagnostics on the Battery. I've read that can make a big difference in mpg.

 

I too have a 2008 and replaced the crappy integrity OE tires with Yokohama's.

My mileage dropped from around 45.5 to about 42.5, but it is a MUCH better,smoother, quieter ride. I have only 2 tankfuls of my regular driving (around town) though. May be a break-in period, maybe tire pressure, which I checked just yesterday (added a little air). Prius drivers get a little spoiled in the MPG's they can get, so it is hard to believe getting 42 or 43 mpg's is bad

 

ONE low tire can make a big difference.

 

Can only say as I previously posted my 2008 went from 51.3 to barely 40.1 after an oil change (reg) and new Cooper Radial tires G54 Touring High Mileage 185/65 R15 I paid $ 440 for these tires I have put on 3,000 miles and still can only get 40. miles per gallon I use 87 grade fuel.

 

Overfilling the oil can make a BIG difference. If the oil is above the top mark on the dipstick it can end up getting frothed up by the bottom of the crank (I have been told), and MPG will drop. I always change the oil myself and find 3 quarts is enough to bring the oil up to the midpoint between low and high. 4 quarts is too much.

My 2008 Touring has 31000 miles on it and it's getting about 53 mpg on the current tank.

 

Hello mmnepps. Have experienced the exact same thing. Everything said in the rest of the thread is conducive of low mpg. By 36000 miles I experienced an inverter meltdown and Toyota replaced it under warranty. Everything is back to my normal. I live in Pa Laurel Highlands at get 49 mpg. Run Hankook Mileage Plus II p185/65r15 (lrr) inflated to 36psi, still good ride, and discipline myself to drive as stealthy as possibly. It only takes a few miles of not paying attention to loose mpg. When I travel east or west off the mountain I'm in the mid 50's. Good fuel, lower oil level, higher tire pressure, locale, clean air filters, a good wax job and paying attention help increase mpg.

 

New tires can drop your MPG. Have you checked the wheel alignment? Also check the wheel bearings.Dirty air cleaner. H

 

Last June the mpg in our 2008 dropped from 52 to 42 mpg. The only thing that changed was new tires were installed. Toyota didn't think that was the major culprit, they blamed it on the Summer gas blend. This week the mpg has increased to 52 again. I use ethanol free gas (confirmed by H2O test), so that hasn't been a variable. If it were new tire break in, I'd think it would be a gradual improvement. With winter gas back at the pumps, I think the gasoline blend is the major factor that impacted our mpg reduction. However, one thing that refutes this is, summer blend should improve mpg, because theoretically it has more energy. Now the question is how long will this continue?

 

That's interesting Lindon, the way your MPG's both declined and then returned so suddenly. The only thing about the "summer gas" theory is that I'd expect a lot of other people here would have noticed the same effect.

Has there been a significant drop in temperature over this last week that your MPG's has improved? If so then perhaps there's something compromised in the cooling of you're vehicle (eg maybe HV battery maybe inverter maybe something else) that is marginal but not quite bad enough to trigger codes?

Let us know if the improved MPG remains over several tank fulls. It's an interesting puzzle.