Do you really need to change the oil?, I'm just playing Devil's advocate here. Options

[VavAlephVav]

Really, aside from the cleanliness and longevity of the motor. How much of a difference does it make on the performance or power output of the motor if you have old burnt up oil that is broken down still in the motor?
Percentage wise how much power do you think you loose from having worn out motor oil that needs to be changed?

10%? 20%? more?

[Box]

Generally the rule of thumb is 5K for conventionals, and 10K for synthetics with some claiming 15K. This would be under normal conditions that the majority of drivers experience. An oil cooled turbocharged motor burns up the oil sooner for the obvious reasons, and a truck that spends most of the time towing fall more towards severe conditions and really need changed more often. One thing to note is when using synthetics make sure to grab an oil filter that's meant to last for the extended duration between oil changes. The thing to do would be do an oil change and then drive the car for about 5,000 miles and send off a sample to Blackstone Labs or the like and they'll say exactly when you should be changing your oil. If you live in a warm climate and do all of your driving at 55 mph obviously your oil will last much longer than someone that lives in an ice box that does nothing but city driving.

This post has been edited by Box: May 14, 2015 - 11:42 PM