Engine flush

[TheSilkySmooth]

Little know or believed factoid:
Used oil lubricates better than new, as proven in many white papers out there from auto industry studies (sorry no links at hand). So, over-changing your oil can actually cause more wear than doing the 5K interval. The mechanism of increased wear is that the high level of detergent additives in the NEW oil (usually a Ca metal organo-metallic) compete with the antiwear agents for surface area attachment. Until the detergent level has retreated(~ 1.5K mi) the loss of excess wear protection occurs. CAVEAT: If you do only short trips <5miles in cooler climates and rarely do highway driving, you may deplete your oil base reserve before 5K and have acid (PH) buildup, though.

[RedRide]

Originally Posted by TheSilkySmooth

Little know or believed factoid:
Used oil lubricates better than new, as proven in many white papers out there from auto industry studies (sorry no links at hand). So, over-changing your oil can actually cause more wear than doing the 5K interval. The mechanism of increased wear is that the high level of detergent additives in the NEW oil (usually a Ca metal organo-metallic) compete with the antiwear agents for surface area attachment. Until the detergent level has retreated(~ 1.5K mi) the loss of excess wear protection occurs. CAVEAT: If you do only short trips <5miles in cooler climates and rarely do highway driving, you may deplete your oil base reserve before 5K and have acid (PH) buildup, though.

Where did you get this info from?
I seached the net and could not find anything at all to back that up.

I have a suspission that the theory that used oil is better was taken out of contex.

[TheSilkySmooth]

Originally Posted by RedRide

I have a suspission that the theory that used oil is better was taken out of contex.

No, I explaned the suspected mechanism. This is not theory, it has been validated by rigorous industry tests. IIRC, it was a GM paper. Think I read the paper synopsis through a link on BITOG but was not able to save it. And its not "used oil is better" it is that over changing oil may lead to more wear due to the fresh detergent action and other factors.