2006 Prius: Does high mileage equal lower mpg?

nah. how are the batteries?

 

Most higher milage prii still get good fuel economy, from what I've read and experienced mostly in the 40's mpg range. My 232,800 prius gets anywhere from 43-50 mpg but I can't get much over 50.
When I drive another prius with 160,000 I can get 55 mpg easily. Honestly you shouldn't be getting that low of mpg. Your hybrid battery is probably seen better days
It might be worth buying a grid charger for it since it hasn't thrown a check engine light.

 

Is that city, or highway mpg average?

 

Sorry for spamming! I had a thought. . How long have you had the car?

Why I ask; when I first got my prius in May, it had sat for a while on a dealers lot. When I first bought it, it was getting awful mpg and the battery was always changing and running down.
But after I kept driving, driving, driving it, the battery performance is much better and I get much better mpg without even trying. Good luck!

 

My 2006 prius gets ~50mpg. My wife's 2008 prius gets ~40 mpg. Back when my commute to work was less than ten miles, my same 2006 prius averaged low 30s mpg in the winter. Short trips, low temperatures, and hilly terrain are all very bad for mpg.

Did you reset the mpg counter when you got it? Test drives included in its average would drive your average down as they are short trips. High oil level above the top mark can also cause low mpg. There are many innocuous things that could lead to low mpg.

If you have a scanguage you can check the csd (charge state differential). It should be 0.0 (is on both of mine), and I suspect anything more than 7.0 indicates imminent hybrid battery failure.

 

You said your tire pressures were 40/42. The convention is front/rear, so if that is true I would reverse those pressures, higher up front.

 

I have a 2005 Prius with a little over 205,000 miles on it, and usually get between 48-49mpg with it still. I have noticed though that the type of tires you have on it make a difference. I used to use good years on it, but the life of them was horrible, but the MPG average was easy to get 52-55mpg. But I'd usually only get about 30-35k out of the tires. I switched over to Pirrelli's and my average MPG went down immediately. But I can get 50-55k miles out of a tire, so I am fine with the trade off since they are nearly the same price, and I hate putting tires on all the time. Oil fill level seems to make a difference too. When I change the oil and put the recommended amount in, it seems my MPG goes down for a while, but once its used up about a half quart, the millage goes way up. Not sure why, and it keeps going up the lower it gets, but I hate letting it run lower than half a quart. I run my tires at 40PSI, so its a little harder ride, but it makes the tires last longer, and I think it helps with MPG. As mentioned, above, i'd check out your battery, and make sure that isn't the problem. Also make sure your airfilter is clogged up, or any of your tires are low on air. Just a few ideas.

 

There was a Consumer Reports review on an old Prius (probably Gen1) and they said essentially good as new as far as MPG. So lower MPG will be symptomatic of a problem or driving habits (short trips etc).