Ecopia 422 - P195/60R15 87H put on original 185/65R15 = LOW MPG

Purchased a 2005 used Prius a few years ago with Michelin X Radials 185/65R15 which got great gas mileage (48 to 55 average and 60+ on long trips). Maintained by Art's Auto a hybrid repair shop in Berkeley. Great mechanic if you are in the area. Art recommends and sells the Bridgestone Ecopia but now I live in Southern Calif in Joshua Tree a desert area.

After maintenance by Toyota a month ago, I decided not to buy tires from the dealership. I read through Tire Rack, this forum and other reviews, and narrowed it down to the Michelin Energy Saver AS and Ecopia 422 plus a few others. I couldn't find tires locally for a good price. Yesterday I was in Cathedral City and noticed a rear tire had a bulge.
American Tire didn't have any Ecopia's or Michelin's in my size. There was a Firestone dealer selling the Ecopia's and at first told me they had the 185/65R15's but then the computer said not available.

Two associates assured me four P195/60R15's would be ok with no hit to mileage. With the tire bulge and the high heat and driving on dirt roads I knew I was on borrowed time and didn't want to drive around looking for the Energy Saver in my size, so I purchased the Ecopia 422 P195/60R15s knowing I could return them in 30 days. I did get a wheel alignment also.

Right out of the lot it felt like I was driving with the break on and even after driving lightly & pulsing after 20 miles, I was only getting 25 mpg. I didn't use Air Conditioner seeing the poor mileage and I drove home getting tops at 35 mpg! This trip in the past would be no less than 45 miles per gallon for the 70 miles home driving up a grade.

I know new tires need to be broken in but I've not read anyone stating such poor gas mileage. I checked the tires which are set to 35 psi so I'm going out to add more pressure and test drive but I've called to order the 185/65R15 tires to replace on Tuesday unless anyone can convince me otherwise.

Why would the first 70 miles be so low? My guess is putting the P195/60R tires on my 185/65 had to have an effect. It must be the width and height change but can anyone explain this or is it something else?
Thanks.
Pat

 

Thanks for the responses. Oil change and maintenance done at Toyota a few weeks ago. Only Wheel Alignment by Firestone.

Drove to town and still no more than 38 mpg. Met a friend and we found a tire clip 2 inches long sticking between the hub cap and tire but not sure if it had any effect but this might be what I felt as resistance when driving out of the parking lot? Tire gage showed one rear tire 22 psi and second 31 psi and 35 psi for front tires. After filling tires to 42/40 psi mpg went up to 54 mpg on the way home.

With increased tire pressure the car felt like I was riding on air yet the ride was louder. Had to turn up the radio due to road noise.

Since the rim diameter is still 15 is there any benefit to changing back to 185/65R's except price? They are $5 dollars cheaper per tire. Would mpg improve with the 185/65R's or is the drive more stable on 195/60's. Before the Prius I had a 1984 Toyota truck until 2010 so I'm more familiar with light truck tires. It seems the difference is minimal between the two tires and while I want the best mileage I also need a sturdy tire able to handle the desert heat and bumpy roads.

Firestone has ordered the 185/65R15 tires as a replacement if I want to change on Tuesday. I'll go for a long drive tomorrow putting it through different driving conditions before making a decision so any further info would help.

 

I should have said the hubcap clip was perpendicular. It was sticking inward with a small piece held on by the hubcap. We noticed a gap and pulled out the metal clip.

These are Bridgestone Ecopia's. I searched online and couldn't find Ecopia's or Energy Savers within 100 miles at Costco, Walmart, Big O, Amer Tire or at my local tire shops in my size. The Base cost to order the Energy Savers at a local shop would have been $140 for just the tire before the other charges. I might have done this to support the local dealer who was the closest with a good rep. Per Tire Rack the closest recommended installer was Big O in the next town with a bad reputation. This is a rural area and local shops stock mostly truck tires. I would have paid $100+ dollars more if I had purchased locally. Not many Prius owners here. I'm keeping the Prius but will need to find a cheap old truck in the future.

I'm test driving again today. The valve stems seem more wobbly than my old tires. Checking the tire pressure we had to hold the stem with one hand while inserting the pressure gage to get a digital reading. The old tire stems weren't as wobbly or difficult to get a reading. This is the first time I've trusted a car to someone other than my old mechanic Art's Auto or Toyota in 30 years! Thanks again for the all the suggestions! I'll be reading more forum responses on how to survive with a Prius in a rural area.