2006 Prius' decline in miles per gallon

Wow, thanks. I did not know about the LLR feature, but I will look into tires with that rating. Joe1987

This is a post I put on the brake problem thread, you might look at this for you lost MPG

What is the complete fix is to take the pads out and clean them up, clean up the shims and guide clips and put them back with fresh grease on the shims and guide clips.

This will also get your fuel consumption back to what it should be.

I had been getting only about 50-52 per UK gallon. (about 41-43 per US gallon)

After I fixed the noisy brake I was getting 55-58 per UK gallon. (about 45-48 per US gallon)

So I serviced the others pads, shims and guides as well.

I am now back to my normal old 62 per UK gallon. (about 51 per US gallon)

The job is not hard but hold the hex on the guide pin when undoing the front calliper bolts or you might damage the rubber covers.

The rear callipers have only one bolt and they then swing up to and slide back off the other guide pin. Then it is just clean everything up and be carful to put it back in the same place it came from. I still have old fashioned brake grease in my tool box, but it seems like Toyota use high temperature anti-seize compound.

Read more: http://priuschat.com/threads/brakes-squealing-at-22-000-miles.112910/#ixzz22FJS59EQ

While replacing the tires with LRR tires will improve your overall MPG's, it doesn't address the issue that your current MPG's have dropped relative to previous fill-ups and the tires are unchanged.

I'd be more interested in checking out the brake solution provided

Thanks for the hint. Although my brakes are working fine (with no noise), I will look into a brake cleaning soon.
Joe1987

Joe1987,

Are you the only person who drives your car? Is it possible that another driver of your car might have knocked the tires out of alignment? I don't know if a bad alignment would explain the magnitude of the mileage drop, but it could explain the suddeness of it.

Thanks for the hint. My car is in the shop as I write this. I have a bent tie-rod that caused the right tire to dramatically lean outward. Both tie-rods are being replaced followed by a four wheel alignment. Hope this helps with the mileage problem.

Joe1987

I did a quick google search to find out causes for bent tie rods and effects. In one thread, a Jetta owner was estimating his MPG loss was around 3 - 5 mpgs. (which he thought was no big deal). Jeez! For a 30 mpg Jetta, that is 10 - 18%. For your car , this might mean a 4 - 6 mpg increase. I hope this resolves your MPG issue!

Hi, well I screwed up again! They replaced a bent strut, actually both struts were replaced. Sorry for the misinformation.

I was looking up bent tie rods and bent struts (symptoms and causes). Seems that most people are concerned about brake shops ripping them off rather than the rods/struts (I'm guessing that a bent strut is an unusual circumstance). Hopefully you are at a shop you trust and they aren't trying to squeeze you for cash.

But mostly, I hope this resolves your issue! Good luck and keep us updated! When you get your car, please fill it up and see if you notice any improvement in mileage over the next few days.

Will do and thanks.
Joe1987

My MPG suffered right before my traction battery died. I didn't realize until after the battery was replaced today that it had been rev'ing higher than normal when going up ramps to the interstate and small hills. Now that the battery was replaced, it is easy to pick out something was wrong.

I suspect a whole bunch of typos. I was thinking, "holy crap! One can still buy bias tires?!?!?" I see Bridgestone Insignia SE200 which are radials and of type R.

I've never heard of these tires and wouldn't be surprised if this is responsible for some mileage hit. No Priuses ever shipped w/these tires.

I just had a bent strut replaced (actually, both sides were replaced) and a four wheel alignment. To my amazement my on board computer just displayed 46.5 mpg. I haven't filled the tank to do a manual calculation, but I love what I saw. This is a rural type environment and not a heavily traveled city like New York, but I'll take it. Who would have thought that a bad alignment can cause that type of decline in mpg's?

Joe1987

Joe1987,

Thank you very much for following up this post. I was hoping that the alignment/new struts would alleviate the worst of your MPG woes.

Check your tire pressures as well. Likely the shop set the pressures at something akin to 33 - 35 PSI. If you pump up your tires to 40 - 42 PSI (42 PSI fronts/40 PSI rears, assuming 42 PSI doesn't exceed your upper pressure limit) you'll see more of an improvement in MPG's and greater tire life, as the higher pressures will minimize tire edge wear (a symptom of underinflated tires).

Joe - I have a 2007 Prius and had been getting 52-53 mpg average. I just had a 50,000 mile service at the dealer and my gas use has gone to 45 mpg. I keep the tire pressure at 35 psi, Michelin tires(Harmony D185/65R15). I checked the oil level and it was above the full mark , about 40%. Another thing that I got from the web is fuel injector cleaner. I will try that.
ErnieM

ErnieM,

The overfilled oil change = lower MPG is well documented on this site. I'd see how removing the excess oil impacts your MPG's prior to a fuel injector cleaner. Most gasolines have detergents in them that would seem to minimize the utility of fuel injector cleaners. That's not to say it won't make a difference, but I'd go after other low hanging fruit (overfilled oil, Tire Pressure) first.

BTW, I don't think your tires are Low Rolling Resistance (LRR) tires.

Harmony | Michelin Tires

Michelin gives them a 6 out of 10 for fuel efficiency for tires of the same class.

Hi Ernie. That's a major overfill on the oil. The dimples on the dipstick are spaced about 45mm, so 40% is about 18mm, that's nearly 3/4 of and inch! Overfilling the oil, especially by more than 1/2 an inch, is very bad. Yes it will decrease your MPG. Worse however it will cause your oil to splash and froth which may result in fouling of your intake/throttle body.

There is a spray can for cleaning your throttle body. Most auto supply store will carry this cleaner. Do a search and you should come up with a blow by blow on how to clean your throttle body. H

One thing I've learned about driving a Prius in Florida is that once the outside temperature gets to about 90+ the MPG drop substantially. I keep my A/C set to 77 and during the fall/winter I will get 45 - 47MPG on my daily commute. When the temperature increases (I keep my tire pressure at 42/40 and check it regularly) the MPG can drop as low as 40. I did all sorts of checks with a Toyota dealer and a trusted independent guy and nothing was coming up.
As soon as it cooled down (high 70s) the MPG would go right back up. This has been the case for the past four years with no dramatic changes to the car...just regular maintenance, oil changes and new tires (which did drop mileage a bit for about two tanks).

Highway mileage which isn't part of my regular commute has always been 40MPG (Avg 65 - 70 mph) not matter what the outside temperature is.