On a new engine I change oil and filter at 2,000mi. After that I change oil and filter every 5,000 miles. On racing engines, after every session. When I have opened up any of those engines they looked new, no crud anywhere. I looks at it like dis--I ain't drinkin' day ol' beer eder cus it gits skunky. It may make no difference in how long anything lasts but it sure makes me feel like I am doing my best to see that it does. It seems logical to me that the more the oil is contaminated the greater the potential for damage as the lubricity degrades, and, they are swiping oil on every stroke. dat bees a lot of hay in the barn. I have no idea how that could be proved either way.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas