I only use my C5 for autocross. I installed a Splitter with under tray not to long ago. I have a choice of 3"x 24" 3"x 18" and 3"x 14" opening to feed the radiator. With the 3x24 the water temp. was fine. 3x18 just a little hotter. I really wanted to use the 3x14 opening. Smaller the opening more downforce, but the water temp. was running 235. Probably a little to hot. I decided to buy the DeWitts radiator with no oil cooling. My last race with the radiator, my car ran 225. With about the same ambient temp. Not a big change, but with so little air coming in, I feel that's pretty good. The radiator is made very well and the fit was perfect. I made fun of there advertising with my friends "Direct fit", because lets face it, nothing is "Direct fit", but this was to my surprise. I'm going to install there "Direct fit" fans and I'll let you know how that goes.