lower mpg with new michelins

finally bit the bullet for a set of new tires, went with the michelin sale in november with $70 off a set of four, why not get one of the high end brands, right? it seems to me that the softer rubber of these guys has knocked my mileage down from 25 to 22, something i measure with every fill-up. Once in a while i put the car in neutral on a long hill (yeah, yeah, it's illegal in many states) and when i did that with these new michelins, it felt like the car just wasn't rolling like it should, not picking up any speed, like i was driving on sticky gumby tires. Of course it's colder out now and that takes a bit off the mpg but i even went with a slightly higher profile to get a few less revolutions per mile of the engine (205-70-15's to 205-75-15's). anybody else had this experience? sorry i don't have the model designation at hand but it's a plain jane passenger/small SUV tire. inflation pressure is fine.

Don't forget, by going to a higher profile tire your odometer readings are affected. Less miles traveled using the same amount of fuel equals lower gas mileage.

As the post above states, your recorded mileage is now inaccurate. Not only are the new tires taller, but they also have fresh tread.
According to my rough calculations, their circumference is now almost 10% greater than the old ones.
So roughly speaking, this would account for 2 mpg of the 3 mpg that you have lost. The remaining 1 mpg could just be measurement inaccuracy or the effects of the heavier tires and the overall change in gearing.

Also some of the softer tires have a higher rolling resistance which will affect the MPG a little.
Jeff

i agree big time first of all i think mich are the best tires made. and yes you changed tire size that will do it. another thing if you never got it aligned your tires will be wearing on you soon? they should have told you this.

looking at a circumference calculator online, the difference is 3.07 %, not much. really just wondering if anyone else has had this experience. these are the X radial, not michelin's high mpg model. alignment is fine.

looking at a circumference calculator online, the difference is 3.07 %, not much. .
not entirely correct. your new tires have fresh, deep tread. The old tires were worn-out, so the new tires have additional circumference that is not taken into account by the calculator.

finally bit the bullet for a set of new tires, went with the michelin sale in november with $70 off a set of four, why not get one of the high end brands, right? it seems to me that the softer rubber of these guys has knocked my mileage down from 25 to 22, something i measure with every fill-up. Once in a while i put the car in neutral on a long hill (yeah, yeah, it's illegal in many states) and when i did that with these new michelins, it felt like the car just wasn't rolling like it should, not picking up any speed, like i was driving on sticky gumby tires. Of course it's colder out now and that takes a bit off the mpg but i even went with a slightly higher profile to get a few less revolutions per mile of the engine (205-70-15's to 205-75-15's). anybody else had this experience? sorry i don't have the model designation at hand but it's a plain jane passenger/small SUV tire. inflation pressure is fine.
Got the same tires (Michelin X) at the right size with the same expectations (better mpg) but still getting 22 mpg overall plus annoying tire slip on rainy days....hopefully the tirewear rating is reasonably accurate to compensate for the decrease in rain/snow traction.

mich are the best tire that i like i bet feels like you put new struts or shocks on huh? if your loosing milage are you running the air pressure the the cars want you to put there recomended or are you going by pressure it calls for on the tires? need to look inside your door and see what they want you to run the pressure at.