...Passat 2.8 L V6? It is a VW Passat 2.8L V6. I just got it and I believe the dealer put regular in it and the manual says premium. Now the car is shaking a bit. Could this be a result of not having premium in it?
Thanks for the help guys. I put some teluine in it to raise the octane of the tank and now its smooth as glass again. Now I know I have to run premium in it.

If you use regular gas you will hear knocking sounds coming from the engine. Nothing is going to happen to the engine it just wont run like it should. Is it cold outside? cars shake when you first start them up in cold weather. Try filling it up with premium to see if the shaking contiues.

This really wont effect the car immidetly. Over time the gunk built up will and you will be faced with cleaning and changing the fuel pump. If the car has received that kind of gasoline forever then shaking will be the result of that...Dont but that car if its used and shakes. You are just going to waist more money fixing it.