Hi I have a 1996 Maxima. I changed the antifreeze over a year ago to the Texaco extended life (orange). I changed the engine oil about 3000 miles ago. I had oil level a little over full all this time. I now have a waxy substance on the inside of the radiator cap and the over flow tank. Could it be incompatable antifreeze or actualy oil in the cooling system? Anybody have any thoughts? I'm going to change oil and flush cooling system but what brand antifreeze should I use? Thanks Greg