The attraction, of course, is that they're washing with their shirts off, allowing you to gawk at their spectacular physiques.
They know it. They plan on it. It's the one time in the Straight World where everyone acknowledges the existence of same sex desire.
Well, not really. Everyone is supposed to pretend that it's all about the cars.
A lot of the car wash fundraisers feature women instead of men, so you have to be careful. Is it a male team or club? Is it being advertised by men? Especially men who wrap the signs around their waists, implying that they are naked.
You also have to worry about the age of the guys. They are typically in high school or college, but occasionally younger groups host car washes. No point in gawking at a group of 12 year olds.
If you're lucky, they'll be even older than college age.
I stay away from car washes with both male and female participants. They invariably try to steer male drivers toward the females, and female drivers toward the male. If you insist on the "male" group, they act as if they have never heard of anything so outrageous.
You're not allowed to just stand and watch the workers. That would make the real reason for the car wash fundraisers too obvious.
But nobody says you can't bring your car in to be washed several times.
See also: The Nude Car Wash; A Week of Beefcake and Bulges on the Plains