Sudden drop in mileage ?

Your problem is you purchased new tires.

New tires will nearly always produce lower mpg numbers because they are new. They require a breakin in period before they will achieve their average fuel economy and from that point they continue to get better as they wear down. When tires wear down rolling resistance is decreased such that a worn out set of tires will have a much lower rolling resistance than the same exact model of tire when new. So expect a temporary loss until the new tires wear down a bit. Now for the really bad news....

If you replace the OE low rolling resistance tires with a set of non-LRR tires then you may never recover your original fuel economy. Even other LRR tires may not match the OE tires. A few LRR are better than the OE tires but usually you have to hope you can match the OE fuel economy and best it with better handling and tread life. The Coopers are not known for stellar fuel economy. Did you not read my LRR tire thread? If you hurry you can probably trade those tires in for a proven LRR tire before your 30day trial period is up.

Low Rolling Resistance replacement tires: Current List | PriusChat

Be sure and read these:
Fuel Efficient Low Rolling Resistant Tires
Tire Tech Information - Tire Rolling Resistance Part 2: Defining Rolling Resistance
Tire Tech Information - Tire Rolling Resistance Part 1: Understanding Corporate Average Fuel Economy
Tire Tech Information - Tire Rolling Resistance Part 3: Changes to Expect When Switching from Worn-Out to New Tires

 

Dump those Coopers if it's possible. My experience with Cooper tires was once and done. Never again. In 5-10,000 miles they'll be so loud you won't be able to hear yourself think.

Read F8L's tire threads. I just replaced the original Avid 33's with Conti ProContact with Ecoplus, and while the handling is GREATLY improved, which I love, the mileage has dropped by a mile or two. At first I was really pissed off, but as I've lived with the tires, I've come to realize that 47 MPG is virtually as good as the 48 and change I got with the Avids. I wouldn't trade back.


REV

 

Rev,

I'm still glad you got those tires. I thought of you and Evan Fusco the other day when my best friend, who also runs those ProContacts, sent me a text that read "Damn! These Conti's GRIP! I just railed an on-ramp like I didn't care about life..." Remember that this is my buddy who raced high HP Camaros and Z06 Corvettes. So while you lose a bit in mpg you made up for in tire life and safety!

 

You're absolutely right, my friend !!

Also, as you and several others have said, the MPG's have come up a bit since they were installed about 2000 miles ago. At first I was very disappointed I hadn't waited for the Michelins, but I'm kind of a performance buff and like to hit a corner or two every now and then (yes ... even with a PRIUS LOL).

My new Focus SE has the standard Conti ProContacts (non-EcoPlus) and I like them too, but they're in 215/55/16. They're nice and grippy too !

Thanks for all the help from all who chimed in about my tire choices !

REV