After putting on after market rims and tires my gas mileage went from 28 to 20?
 

Is this normal? Immediately after installing wider rims and tires(I'm going forced induction some time next weekish) I noticed my average kept dropping and dropping slowly over a few weeks. It was at a consistent 27-28, now it's 19-20 and will not go above 21. Is that normal?

Yes.
Wait 'till you get FI on there!

What kinda whims did you get? Similar to this?

https://s13.postimg.org/4gkgcoilj/Capture.jpg

OMG THIS SO MUCH!!!!

Fuel economy sucks total balls with the turbo now. 12L/100km highway is good for me now its :bs: lol. Its fun but cost too much in gas now

Well there are alot of things to consider here.

1. Whats the Size of the new wheels (Rims as you call them)
2. How much does the new wheels weight.
3. How wide are the new wheels.
4.How wide are the new tires?

Thats the short version of the list of why did my gas mileage go in the shitter.

In addition to wheel weight and tire weight, you have to factor if the new tires have a higher traction rating than the tires they replaced. More traction means more grip, which means drop in fuel economy.

One other consideration is the gas. Your area may have switched over to winter blend, which will give a drop in mpg.

I have the same mpg as the OEM wheels and tires when I have my 17x9 TC105N with 245/40/17 Continental tires.

Yes, larger tires will measurably lower your gas mileage, but likely not that much. Consider other factors that might contribute.

This is because 17x9 on TC105N with 245/40/17 is almost the exact same weight as the stock setup.

Heavier wheels/tires and more roll resistance arent going to reduce mileage by almost a third. And, there isn't the need for winter gas in FL. LOL

Im going to go with a heavy foot, multiple short trips and possibly the ethanol content of the fuel you used might be higher than previously.

That's way too large of a drop in gas mileage.. something is wrong

unless your car looks like this
https://s3-eu-west-1.amazonaws.com/a...6f4c54407d.jpg

TireRack measures fuel efficiency in their tire tests. The differences in efficiency between similar tires can be surprising. For example, there was a 5.3% difference between the best and worst tire in this Max Performance summer tire test:

http://www.tirerack.com/tires/tests/...y.jsp?ttid=218

Note that this test is done with tires of identical size.

Now if you were to go from a low rolling resistance narrow tire like the stock Primacy on stock wheels to a much wider, stickier, heavier tire mounted on heavier wheels, I would expect a significant reduction in fuel economy. The wheels and tires probably aren't the only factor, but I wouldn't be surprised if it accounted for 2/3 of the drop.

Lol. That was my point for the OP. It's hard for us to say anything without more info.

http://www.platts.com/latest-news/oi...uests-21401095

They still receive varying blends of gas. May as well call it winter blend since it's different from summer blend.

I was getting close to 27-28 stock as well and with wider/stickier tire I get 24.5 (245 MPSS on x9 light weight wheel). Dipping beyond 20 seems pretty excessive, but depends on the way you drive I guess is possible, or you have some other factor. I can't imagine you drove aggressively and got 28mpg on stock, similarly, I expect you don't drive much different with wider tires now.