Since I switched out my stock 16" All Seasons to the Blizzak's LM-25 I've noticed my avg mpg has dropped from around 32 mpg to around 27mpg.

For some background, I have 16" all season and 17" snows. I know, its backwards. I bought a used set of 17's with the Blizzaks already mounted. Also, I am doing a bit more city driving now then highway, but I think that should only be about a 1-2 mpg drop.

Anyhow, anyone else having this issue? Is it because i went from 16's to 17's or is it the Blizzaks?

Also, how do you know when the winter tires need to be replaced?

 

I too had a slight drop in mileage when I switched to my snow tires, but I think is may be more because of the ethanol that they add to the gasoline in Colorado during the winter months than it is to the change in tires. I noticed this last year as well when I didn't run snow tires, my mileage went down in the winter. Aslo if you are driving in snow and slush expect a drop in mileage as there is more resistance.

Also switching rim/tire sizes will cause a change in your odometer reading unless you are matched up to the same rolling diameter you had before you switched. Check with the rim/tire charts that are available on the web.

Replace your snow tires when they no longer provide the grip they once had.

 

wat size tires are they?

also if you use more defrost mode (a/c) you will kill mpg.
along with winterized gas...

might be best to do a back to back comparison in the
warmer months without using a/c.

 

it's a combination of both. Your wheels got heavier since you moved up to 17", also tire is softer and creates more ressistance on dry road vs. all-season tire. This is why you're seeing decrease in MPG.

I usually put my summer wheels with tires on when it's around 40-45degrees in majority of days with no or slim charces for more snow. It's usually around end od March or begining of April.
Winter tires go on around Thanxgiving.

 

yeah, all the points were pretty much covered.
i found that driving in the city dramatically dropped my mpg, alongside with heavy wheels. I'm currently trying to switch out my heavy wheels with something a little lighter to help with that.
also just keep checking your tire pressure to get as much miles you can milk out of your car

 

I went from the stock Dunlop 195/55/16 runflat hockey pucks running at 36psi to 205/50/16 Michelin Primacy PA3's at 33 psi on the same stock wheels and noticed a slight decrease on the odometer as well (takes different diamter into account). This despite the snows being a lighter tire. Guess the combination of tread compound and width is the culprit.

 

Doesn't cold weather in itself reduce mileage? I have noticed this in other cars as well.