Summer vs Winter performance

[Schwalby]

Ok so I know that vehicles will usually perform a little different from season to season but it seems my rig is taking that to an extreme. I live in the northeast so we get a pretty decent fluctuation in seasons and my rig seems to drastically perform better in the summer. Some of the things I have noticed are I gaining about 4 MPG during the summer, I reach 70-75 MPH with no problem in the summer were as in winter I need to be going down hill and have a tail wind to barely hit 70, acceleration is a huge improvement in summer, and ride is drastically smoother. There are other fine points as well that change but those seem to be the big difference. Now I have a 4Runner that I drive also and it doesn’t really change at all from season to season maybe it gets 1 extra MPG and that’s it. The only thing that has changes from winter to summer is I take the hard top off and put a sunrider on. I also put on BFG AT in place of the stock tires this spring but no size difference, but may contribute to the ride being smoother.
So only thing I can think of is that the temp difference would be making fluids and what not stick or run stiffer. And that doesn’t sound like it should happen or be a normal thing. Any ideas on what to check or is this a possible larger problem. I rarely drive my Jeep in the winter so if this is just another one of those “Jeep things” I am cool with that. Just don’t want to ignore or miss a possible problem.
Thanks

[CCrew]

Quite possibly a gas blend problem. Lots of difference between summer and winter blends. You should be on summer blend gas by now....

-Roger

[SJP]

There is a change in the gas blends in NE that does adversely affect gas mileage during the winter. When combined with the cold ambient temperatures, that causes more gas to be consumed to achieve the proper fuel mixture, I see a drop of about 1 mpg, both around town and on the highway.

The significant gain in mpg that you are seeing might be that paired with the new tires. The BFGs should have a stiffer sidewall than the GSAs, which would effectively be like overinflating your tires to get better mpg, not to mention the smoother tread pattern.

[Schwalby]

Ok that would explain the increased MPG (wish my truck would do the same). Would the gas blend also explain the increased top speed and over all power boost? Also I would think the BFGs had a more agresive tread then the GSA, what am I missing that point?

[SJP]

While being more aggressive, I would say that the interlaced nature of the tread pattern yields a more consistent pattern than the individual lugs on the inner portions of the GSAs.

The summer gas blend should result in the better performance that you're experiencing.