I have a car and will offer a ride if it's not far out of the way, or sometimes if I know that it will be very very inconvenient or expensive for the person to get home otherwise. I don't regularly offer rides that will add more then twenty minutes to my trip home. The exception is if someone has done me a favor, then I'll almost always offer a ride. I'd be mad if someone expected me to go more than twenty minutes out of my way, barring very exceptional circumstances.