This is one of my favorite classic commercials from the 70's. It aired during 1974 and '75. The following info is from a Me and My RC promo LP:

"Stock Car" was shot in Gardena, California during two memorable nights. Maybe it never rains in Southern California, but man, it sure gets cold! It was 35 degrees, and the script called for a balmy summer's evening. So we moved people through their paces with strategically placed heaters blowing warm air to keep their breaths from showing that they were really freezing their RC's off.

Click the link below to see the commercial. 1970's advertising at it's best. The guy singing the Me and My RC tune sounds like Glen Campbell. Check it out! :D

https://www.youtube.com/watch?v=Wm_LmlFeNnM

I believe the commercial you are referring to is the RC Cola commercial that features a race car driver competing in a car race and then he celebrates his victory with his girlfriend and his buddies by treating them to cups of RC Cola. I don't know when in the 70's this commercial launched but I happened to see it a few minutes ago and after I saw it this thread had to be answered. The singer singing the Me And My RC song is not the late Glen Campbell but an unknown singer
Bestie