My mpg went from 35 to 29 on the interstate after replacing the Michelin mxv4 tires to the Michelin premier a/s
Ok, sounds like the Premier A/S is not as fuel efficient as the MXV4. Check your pressures, too. If the are low that will affect it as well.
Looks like the tires are pretty comparable for nearly every category on TireRack.com. Price is even close.
Are the new ones exactly the same size as the old ones?
Tires that come on new cars are specially designed to the vehicle manufacturer’s specs - and among those specs is improved fuel economy (low rolling resistance). To get that, treadwear and/or traction are sacrificed.
Tires sold at local tire dealers do not have such specs and since treadwear is a very important parameter for the customer, the fuel economy (rolling resistance) gets sacrificed. So unless you gets the same exact make and model of tire, you will take a hit in fuel economy.
Further, new, unworn tires get worse fuel economy than worn out tires - so there’s another hit.
Lastly, the Michelin MXV4 is UTQG rated for faster wear than the Premier A/S, so that’s a third hit in fuel economy.
Bottom-line: If one replaces OE tires, one should expect a fuel economy loss, especially if the treadwear of the replacement tires is better.
And for those that are interested, the Federal Government (NHTSA - National Highway and Traffic Safety Administration) is supposed to publish on March 30, 2020 proposed regulations concerning the testing and publishing of tire rolling resistance. This will be the 3rd time this was supposed to be published, but each time the date was postponed, so I am not optimistic.
The first time it was published, there was a HUGE pushback from the USTMA (US Tire Manufacturers Association). Not only was EVERY size and model supposed to be tested (which would take 3 years!), but the Feds wanted to publish the values in terms of Force, and the USTMA wanted Coefficient. Coefficient would result in tires with lower RR having smaller numbers, where Force would result in larger numbers and the possibility that an unsophisticated consumer would buy a SMALLER tire - the wrong way for safety!
The proposal was withdrawn when the GAO (General Accounting Office) agreed with the USTMA.