According to Racing Sports Cars, the NSU Sport Prinz, driven by Fred Fischhof came in 1st among GT600 cars at the 1961 Sebring 4 Hour race. (It came in 13th overall.)
Shortly after the race, Fischhof was interviewed by representatives of Gulf, and provided this response in the advertising they ran later that year:
RED BARBER: (to Fred Fischhof, Class 3/4 winner in NSU Prinz) "As another driver who ran on Gulf, and won, what do you have to say, Fred?"
FRED FISCHHOF: "Like you say, Red, Gulf Crest really burns clean and keeps the carbon under control. The car didn't miss a lick. It picked up quickly out of the curves and hit peak power on the straights. Maybe I have a little extra reason for saying so."
RED BARBER: "What do you mean by 'a little extra reason,' Fred?"
FRED FISCHHOF: "Well, I drove the smallest car in the race at Sebring. So it was a most responsive one. I could be sensitive to even minor differences in performance."
OK -- now you've heard it from Red and Fred.
(NB: We suspect this is a "file" photo, since Fred's winning car was number 34.)