Is it better for a NASCAR driver to be out in front and have the clean air or be behind another car for draft?

May be...

It all depends on the handling of the car. Some would be better in clean air, and getting the nose pushed down for more down force. Others would be better with their noses in the ahead cars rear, just riding around in the what I would say "eye of the storm", nice and calm clear. It also depends on driver preference some like to hang back and let others break the wind, while some wanna lead and take charge of the car.

At Daytona or Talledega draft is better. At any other track clean ar is best.

Out in front makes the car faster, but more speed = more gas. So running in traffic is better on the tank, but not the speed and handling.

The draft effect, because the car isn't working as hard punching a hole in the air as the lead car, therefore less fuel is needed to power the car, even though the lead car has clean air. It also helps with downforce, because the air coming off the rear of the lead car is coming down onto the nose of the 2nd car, pushing it down into the track. Depending on how well the 2nd car is handling, this could make the handling better or worse, but the 2nd place car will be faster and I think more fuel efficient.

With the COT, being in the front with clean air is alot better than drafting dirty air with a car thats half as sucky as yours on nay given track

On the superspeedways it's better to "draft".
Like how Keselowski did when he took Talladega
otherwise, "get outta my way"

the tracks is most important

In the COT it's best to be out front except for at Talladega and Daytona. A car in front at any other track than Talladega and Daytona tends to have a slight advantage and runs off from the pack. If you have a drafting partner that will stick with you at Talladega and Daytona and will settle for a second place finish then it's best to be out front but the way the new car is now all a driver has to do is push a car to lead and at the last minute move to the inside for the pass and win.

It depends on the car and track.

Some tracks it is better to be in a group and draft. Like at Daytona or Talladega.

Others it seems to be better to be in the "clean air".

I was wondering if a NASCAR driver would get better gas mileage and/or speed if they were out in front or behind another car getting a draft effect?

Clean air for the turns, and drafting on the straights..
Edit: Awe c'mone you guys.. When are you going to learn to not take what those guys in the booth say as the whole story.. You need to pay more attention to Brewer (I know he's boring, but he's one of the legends), And Hammond (he's another), and Petree, (Andy knows his S__t.. he won Championships with "Iron Head"), and I never thought I would say this, but even Larry Mac (he must be reading stuff, didn't know he could do that.. I mean read).. The reason guys stick their nose out in a turn, right, or left when they are following someone is for clean air.. They are not always trying to pass.. Then they duck back in behind the guy after the turn, is exactly what I said..
Clean air in turns, and draft in the straights.. At every track..
Maybe not Dega, or Infineon..7650 nokia program