Milage double whammy

[Laserbait]

Ok, so I bought new tires for my Mounty 2 weeks ago - Kelly Signature Safari in 265/60 R18 (replaced the awful bridgestones in 235/65 R18), and love the way they look! Ford really should have used that size from the get-go, and as a plus, my speedo is accurate again!

Also, the temps have dropped & we are now using the "Winter Blend" of gas (by what I was told), and my fuel economy has tanked from mid 17-18 MPG to about 15 on the last fill up.

So, I know that colder weather affects MPG, and the slightly taller/wider tires would to mileage, but it was still a shocker. Is it normal for cold weather to affect MPG so much in the Explorer/Mountaineer?

I don't have anything to really compare it to, since my old mountaineer (a 98) had broken it's odometer at 157K miles 5 years ago. I never really paid attention to economy, just the gas gauge - ignorance was bliss...

 

[Varsity]

Mmm it's definitely possible. I'm not a scientist or anything, but cold weather can definitely affect mileage. "Winter blend" of gas can have a little effect, sometimes 1-2 mpg in itself right there, and cold weather takes its toll because it may take a little longer or more driving for the truck to warm up like normal, especially if you're one of the "jump in and go right away" types. I've noticed my truck lately takes a bit longer to warm up and definitely if I have the heat going from the start and since cold engines don't burn as efficiently, you may be seeing that.

But yeah, it's possible or at least I personally could believe it.

 

[BigNutz]

The warming up thing is a valid point, but the main reason your mileage goes to poo in the winter is the air density. A given volume of cold air is more dense than the same volume of warm air. So with the more dense air, the fuel mixture program adjusts to a richer fuel air mixture to obtain optimum ignition. More air means more fuel means less range.....But it should mean some more power!!! Hey that's good news!!!!