When extreme overheating situations exist, oxidation is rampant. The only cure for oxidation is changing the oil. Extreme heat indicates the need to change your oil more frequently.

Your fossil oil's effectiveness in lubricating drops off once its temperature increases beyond 250" F.

Oil Oxidation Rate Chart

When observing the accompanying oxidation rate chart, it will become readily apparent that heat is the enemy and must be controlled. With heat comes oxidation of the oil and the only cure for this is to change the oil. When extreme overheating situations caused by improper tuning or a brutally hot summer day exist, oxidation is rampant, so change your oil more frequently.

http://www.imagespeech.com/out.php/i182_OilBreakdown.jpg