Help: Mileage Drop - Costco New Tires (Bridgestone Ecopia 422)

What brand of tire did you have on it prior? Have you done a search on this site?

 

It usually takes 1-2000 miles for tires to break in and give max mileage. Your old tires were very broken in, so its not a fair comparison. The nitrogen has little to no advantage over regular air (which is mainly nitrogen) and shouldn't hurt. You can reset the maintenance reminder yourself, but it doesn't make any difference in mileage.
How's the weather been since you got the new tires? Colder temps can make a big impact on mileage.

 

Don't get discouraged by the hyper-milers who go to some rather extreme lengths to get those kinds of numbers. They might be something to strive for as you learn some of the techniques, but unless you have similar routes, traffic patterns, etc., those kinds of numbers are difficult to get and maintain. And some of them spend a lot time finding a route to give those numbers just so they can post them.

I don't quite understand why people say worn-in tires get significantly better mileage. Unfortunately, we took a long trip shortly after buying our Prius, so I wasn't able to see if the mileage increased over the same routes as the tires wore. I suppose there is some benefit, but I find it hard to believe that would make you go from 47-48 to 40-42 without something else changing, like ambient temperatures, and that doesn't seem likely in San Mateo.

If you read all the tire threads, you'll see that people have very different experiences with the same brand/model tires. I've read where people go from Yokohama to Bridgestone, Michelin, Goodyear, etc., or vice versa and have totally opposite results. I've also read about people who experimented with air pressure and saw no discernable benefit high or low. I also don't understand the wheel alignment thing, but I'm new to Prius and have never had to have the wheels aligned on any car I've owned just because I got new tires, or even new wheels for that matter.

 

Many people report a small increase in mileage after the first couple thousand miles. Not enough to be OP's whole issue, but add in lower temps (which makes a bigger difference on shorter trips and city driving) and winter gas and a 5MPG drop isn't out of the question.

 

What pressure did you run the old Yokohama's at? What model were they specifically, if you recall?

There's a fair number of variables at play since the change, not the least being the time you had the new tires at 32/34, before raising them. And the spec is 33/35 (rear/front) I believe.

The alignment was likely not needed, if you haven't hit a curb or similar. Hopefully hasn't messed things up. Does the car feel/steer the same since the alignment? Do you have a document, showing the alignment, any adjustments?

How worned were the Yoko's? It's not a big difference, but going from down-to-the-wear-bar tires to brand new, in the same size, there's a slight increase in the outside diameter of the tire, which will make the car think you're travelling not as far. It can amount to 1.5% reduction in O.D..

Also, weather, traffic might be factors.

All in all, I suspect you're going to end up slightly lower in mpg, because the EP422's are not equal to the Yoko's. But not by much. See how it goes after a tank or two with the higher pressures?

 

Maybe the search function here is broken.
A LOT of users seem to be saying this lately.
There should have been a lot of hits, depending on what you searched for.

 

I'd just search from Google homepage. Something like "priuschat ep422".

 

Tire pressure IMO hurting MPG ,,,,, 42 front 40 rèar , you will notice better MPG ,,, also
If you are in winter temp area , would advise grill blocking