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How do I improve hybrid fuel economy

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Dear Scotty

After having a stroke, I needed an automatic. I wanted a car that's also economical so I bought a well-used, but not particularly well-looked-after, 185k miles 2006 Gen 2 Prius T Spirit. I live in the UK and the car is UK spec. I changed the oil and fluids and the oil is still clean after 2k miles and there are no leaks or fluid consumption. I also used a bottle of Toyota injector cleaner in a nearly full tank. (I realised after putting it in that it was for diesels!!) The final drive (?) is a bit whiny but I can live with that.

I don't do many miles in a year (about 4-5k) and I drive conservatively but only get 49-50 mpg. My gas bills and the car computer tally on the economy. As Imperial gallons are 20% bigger than US gallons I'm getting about 40 mpg in your terms. I get this consistently, although around town it drops rather than increases, and longer journeys (100 miles+) bring the average back up. This seems pretty low. I've put in new Denso plugs but I have slight missing at tickover and low revs.

Could this be bad coils? Also, I bought some BG EPR treatment. Should I use this?

I'm really happy with the car and everything still works, except the OBD port, but I could do with a few extra mpg.

What do you think?

Best wishes from Olde England!

John

5 Answers
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I think that @Dan has hit on something - if your hybrid battery was in bad shape, you would get somewhat lower fuel mileage on trips, and, unlike "fresh" hybrids, would get even worse mileage in town.
This video shows how to check the condition on a Prius battery - there would seem to a number on Youtube.

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Keep in mind that most owners are getting only slightly better mpg.

https://www.fuelly.com/car/toyota/prius/2006

"Based on data from 381 vehicles, 38,088 fuel-ups and 13,030,510 miles of driving, the 2006 Toyota Prius gets a combined Avg MPG of 43.58 with a 0.07 MPG margin of error."

 

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You could try replacing the PCV valve at about $6 US.  It's probably original to the car.  This is just a guess.  You really need the get the OBD system working to correctly diagnose and fix the problem.  Otherwise, it's just going to be throwing parts at it.

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40 mpg in your terms. I get this consistently, although around town it drops rather than increases

The American EPA has estimated the Prius to get 46 US mpg combined, so after all of this years still getting 40 is not bad at all. getting over 85% of the EPA rating is quite good in general.

Maybe the battery is getting worn - but I'm unaware of a good way to check it on a Prius.

185k miles 2006 Gen 2 Prius (...) I don't do many miles in a year (about 4-5k) and I drive conservatively but only get 49-50 mpg

I'm unsure if that's a car you should keep - it's a high milage 16 year old car, with 16 year old batteries.

If you don't drive much, the increase in economy usually won't offset the currently high purchase price (on the 2nd hand market) and the costs associated with a battery replacement down the line.

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PCV valve would be the first thing I would try.

Also. The hybrid battery is kinda old, so that may also explain diminished MPG. I know when I changed my hybrid battery out when it was time, I got an increase of several MPG off the bat. 

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