You give him head.

Shaking, you lean over and suck in Greg's dickhead, tasting his pre-cum.

"Suck it down." Greg instructs you as he pushes your head lower, his shaft reaching your throat.

Greg starts the car as you lick and suck.

For the next ten minutes, Greg drives around with his massive cock in your mouth. You lose track of where you are and how long it's been in the midst of the blowjob. Eventually, Greg cums and fills your mouth, satisfied.