We have a 2010 Prius 2 bought in June. I commute daily 120 miles most all highway. On the day we bought it we were thrilled to get 47 to 48 mpg which I continued to get. Even getting 52 mpg on a flatter road. However it had original Michelines with horrible highway noise with poor grip and handling. I got new set of Cooper S5 touring tires. Remarkable difference once we also got noisy rear wheel bearings replaced. But I've noticed the mileage has decreased to 43 to 45 mpg. Both the tire salesman and dealer approved of the tires for use on the Prius 2. This has only been in the last week all this was done. Any ideas on loss of mpg? Tires still too new, not getting the grip for instance? I was expecting to see as good or better mileage.
The Cooper Tire website information is only saying both S5 tire versions (Grand Touring and Ultra Touring) are not LRR tires. Their wordings may be misleading. It reads: "New generation coupled silica compound provides exceptional all-season performance, improves braking and lowers rolling resistance." Note : "lowers rolling resistance", not "Low Rolling Resistance". So getting higher gas consumption than LRR tires is normal. When you say "Both the tire salesman and dealer approved of the tires for use on the Prius 2", they probably "approved" it for the correct tire size fit. Remember, the more road grip the tires give you, the more gas it will use. You have to find a balance between your desire tire grip and desire gas consumption.
welcome to priuschat! there's really nothing else to add.unfortunately, just because they approved the tyres, doesn't mean they get good mpg's. try higher pressure as david ^ suggests, wait a few thousand miles to see if break in helps, and if there's no improvement, you'll have to replace them with low rolling resistance tyres, or live with the mpg's. there are plenty of tyre threads here, and plenty of actual reviews and comparisons. all the best!
