Do you have an auto or manual transmission?

There can and theoretically should be a noticeable difference in performance/efficiency between 70*F v. 90*F, but it won't be huge, all other factors remaining the same.

 

sport auto

 

I put the wider mugen front spoiler lip on last night and 3 highway trips today my gas mileage went back to normal before i put the wheels on. so it had to have been that the front tires and wheels were sticking out to much and causing aerodynamic problems. before when looking at the front of the car i could see the tires and wheels sticking out past the bumper but not the fender. now with the mugen front bumper cover everything is flush. also my swift springs came in so i will put them on tomorrow and set the alignment. oh and take some pics.

 

well winter here is in the 50's, and summer is as high as 110 intake air temp

 

Even with the KWSC inter cooler the intake air temperatures are as high as 130 + degrees with the low 70 degree temperatures we are having right now... About 110 degrees is normal right now at 45 to 60 MPH staying out of the open loop mode, about 30 to 50 degrees less than without the I/C and hood louvers.....The 16"X7" wheels on my car now are lighter that the stock alloys but much heavier that the RPF1s in 15"X7". They may be taking my mileage down 1 or 2 MPG I suppose because the width of the spokes, offset and weight.

 

 

 

i call bs lol pics of a scanguage or it never happened hahaha

 

the temperature won't make 10mpg difference that's for sure. unless you start and idle your car a lot more in winter, otherwise you should get more or less similar mpg.
lighter wheel SHOULD improve mpg, unless your offset is incredibly off causing it to stuck out and disrupt air flow... otherwise with lighter wheels, it should ALWAYS improve mpg and handling altogether.