I am pretty sure that the issue is not with "them thinking about you and what you drive" - nobody gives a damn really. The issue is about "you thinking what other might be thinking about you and what you drive". So the problem is really internal to you. You just need to fix that up there in your head.
Well, that is of course if you don't have so called "friends" that poke fun at you for driving a van. Drop these friends then.