Cooper CS4 (T-rated) Gas Mileage
by Bill T.
Before buying tire replacements for the Bridgestone EL400 OEMs on my 2009 Honda Civic Coupe, I read everything I could find about the Cooper CS4. I noticed several reports of poor mileage and also Consumer Reports rating of the CS4's rolling resistance was below average (which affects mileage).
I liked everything else about Cooper CS4s so decided to try a set with a mind to returning them within the 45 day trial period if the mileage claims were true. After all, a 10% MPG difference (3-4 MPG) over the 80k mile expected life would cause a significant total cost difference. Here's what I discovered based on careful measurements and a relatively constant mix of local and highway driving by the same drivers:
Last 2298 miles on OEMs (firstname.lastname@example.org): 35.09 MPG
First 2204 miles on CS4s: 31.60 MPG
First 625 miles on CS4s: 30.24 MPG
Last 566 miles on CS4s: 33.96
Conclusion: Initial mileage is indeed worse, however it appears that it greatly improves after ~1500 miles of break-in. My guess is it will continue to improve slightly, so I believe the mileage concerns are overblown and not supported by facts.
I also believe Consumer Reports only tested the rolling resistance of new tires and failed to retest after a break-in period. I did my measurements for my own curiosity but wanted to post this publicly since it may be of interest to others. Hopefully it will offset some of the reports circulating on the Internet about poor CS4 gas mileage. Also, for anyone else with a Honda Civic Coupe, the best cold inflation pressure I've found is 39 front and 37 rear. Using this pressure, I got 33.8k from the Bridgestone EL400 which has a poor UTQG mileage rating (400 vs 780 for the CS4-T).
So far I'm pleased with everything (ride, handling, noise and mileage) about the CS4s...and they're made in the USA to boot!