Mine MPG dropped from about 26 down to 22.

 

My results follow pretty closely with everyone else... 17-24 MPG. I used to get 24-28 before the SC.

 

In theory this is true, but in reality having your car tuned with a standalone can increase your gas mileage over stock. With the car stock & an '00 ECU I got 20/23mpg.
Tuned on AEM I get 23/29 MPG, with a supercharger. Obviously staying in boost will kill your MPG, but I dont floor it everywhere I go.

 

top down NA on highway 26mpg no tune
top down SC on highway 25mpg AEM tune 10psi

I did put my foot in it a few times, I would say that with a tune and driving it easy it will stay unchanged

 

all city mileage i get worse than when i was N/A. All highway i get better than when I was N/A (thanks to my tune).

 

I average 22mpg City/Highway/Traffic DD to work. Now around 20mpg but it's all worth it you gotta pay to play

 

Mine improved.

A solid and repeatable increase in mileage. Usually got 190 per tank (10 gallon fill), now regularly bust 230.

It has parasitic drag, yes...but a centri isn't much, especially in city driving. Given how easy they are to spin by hand, the loss can't be much...remember 1 Horsepower is actually a lot of energy.

I'm on the stock ECU, but I try not to run it super rich. I normally shift to at a point to where there's SOME boost, but still a relatively lean AFR.

 

True, a tune could change that. But the same tune done on your car NA would make better gas mileage than your car now. That would be an apples-to-apples comparison. Comparing an untuned car to a tuned car here is not a fair comparison.

 

I definitely get worse gas mileage now than I used to NA. I still get usually around 24-25 mpg with mostly highway driving, however I drive 80+ on the highway.

I used to get around 27 mpg or so I believe.

 

For me I didn't install a SC to get better mileage, if that's a concern for you I would stay NA.