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I know this has been covered but I can't find the thread. As I approached 5K miles my MPG got better & better. I was getting 51mpg regularly in city driving (I have ~ a 25-30 minute commute to work).
THEN....I had my 5K service. Oil change, tire rotation, etc. My dealer service tech said he knew what to do. I rechecked & changed tire pressure and checked oil level. It was overfilled so the dealer let some out w/o too much complaining.
But, my MPG has plummetted..... Went from 51 to 45, and that's the best I get!! It averages around 43. A 10MPG drop seems kind of extreme. Plus no matter how I drive I can't seem to get in "Stealth Mode". Everytime I touch the accelerator the ICE comes on.
Anything else I need to check?? Could the wrong grade of oil (e.g. [email protected]) cause this? Any ideas??
 

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After my first service, my mpg dropped, too, but only by about 4 mpg. Sooo, I checked the tires. Each was a different pressure! And this was despite assurances that the repair weenies had checked the pressure (cold) and set properly. One tire was at 26, another at 38. I put them back where they belong, and now mpg is normal again.
 

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If your dealer put in 10w30, they are not using what Toyota specifies. I don't quite understand how multiweight oils really work, however I think 10w30 is "heavier" than 5w30 and as such that might have an effect on engine performance, especially with tight tollerances.
 

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I had my first service. The dealer put in the correct amount of the correct grade of oil and the tire pressure was fine... just adding a data point! Some dealers seem to get it right!

I did get low mileage on that tank, but the trip to the dealer was one of many "errandy" trips that week, so I attributed it to the lack of longer drives.
 

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SECONDARY TIRE BREAK-IN !!!
SECONDARY TIRE BREAK-IN !!!
SECONDARY TIRE BREAK-IN !!!
SECONDARY TIRE BREAK-IN !!!
SECONDARY TIRE BREAK-IN !!!
SECONDARY TIRE BREAK-IN !!!
SECONDARY TIRE BREAK-IN !!!
SECONDARY TIRE BREAK-IN !!!
SECONDARY TIRE BREAK-IN !!!


Most people forget about this MPG influence.

You will experience break-in a second time when new tires are rotated to the front for the very first time. The front ones have already worn down to a happy state, but the rear ones had not. They did not experience the wear caused by turning, so they still have a fine rigid edge on them which results in a grabbing effect.

How much of an influence this has is open to debate, but the fact that it does cause MPG to drop is not. I've witnessed it 4 times now on my 2 Prius with 4 different sets of tires over the past 97,000 miles.
 

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The problem with checking and resetting tire pressures when you go in for a service is:
1. you just drove to the dealership, so the tires are no longer being measured at cold. If you check the tires the next morning after not being driven overnight, you'll see that they're lower than you thought.
2. The dealership's garage may not be at the ambient temperature as outside. (more common in the wintertime, with heated garages compared to below freezing outside, so you get a temperature/tire pressure drop when you go outside with your car)
 

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mrv said:
...you just drove to the dealership, so the tires are no longer being measured at cold. ...The dealership's garage may not be at the ambient temperature as outside.
Ah, true. My service garage is under a mile away, and I dropped it off directly from home, a couple of hours before they got to it. So, I think I still fall within the relatively cold tire measuring. And for them to be THAT far off (one at 26 and another at 38 ) cannot be attributed solely to heated tires. Some could, though. I tested and filled them (in the driveway, cold) a couple of weeks later, after 2 or 3 miserable mpg tanks.

BUT!!!! I forgot about John's secondary tire thingy. Sorry, John - I'd read your website and read and read, and STILL forgot. :( Perhaps the combination of "fixing" the pressure and getting the rest of the tires' pointy parts worn off made the difference. :) SOMETHING did!! :D

Oh yah... I flipped 10,000 miles this past Saturday! YAY!!
 

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My 05 Prius has just over 5,000 miles and the Maint Required light is now constantly on. I've been reading the threads about oil changes and not overfilling. How can you tell whether the oil change was not done using 5W-30 oil without you supplying the oil? Unless you are watching them, how do you know that even if you brought your own oil, whether they end up using their own oil and keeping the oil that you brought?
 

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How do you know.

In that case, how do you know that they don't spit on your food when you go out to eat. Now and then you gotta have faith. You can't go thru life mistrusting everyone.........Agile
 

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:roll: In my "2004 Owner's Manual" page 122 there's a paragraph labeled "(j) Engine Oil Replcement Reminder Light (for vehicles sold in the U.S.A.)" which explains the oil change reminder light and contains instructions on how to turn the "Maintenance" light off after an oil change. Likely, the '05 Manual page number is the same.

There's a wealth of helpful information in your Owner's Manual. :idea:
 
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