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Originally Posted by Biz-z Z
That is counter intuitive. I have always thought that the fresher the oil, the better protection I would have. As the oil became more "seasoned" its protective properties would slowly degrade until the protection approached minimal standards, at which time an oil change was recommended.
Is there some advantage in changing the oil between 8500 and 10K as opposed to the Porche's recommended time table?
Would your recommendation be the same for someone who drives say 4-5000 miles per season (May through Oct) and then puts the car away until the following season?
Thanks.
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Hi,
Yes it is surprising. The Test was conducted by Ford Motor Co., Blackstone Laboratories, and ConocoPhillips, and reported in SAE Technical Paper 2003-01-3119. The Test Samples were drawn from a Street-driven Car with 35k mi. on the engine. The Samples were analyzed for Viscosity, TBN (Total Base Number - a measure of Acid combatting Additives), Wear Metals and Insoluables (solids). After each Oil change, the Wear Metals rose significantly for the 1st 3 1000k mi. samples drawn, indicating greater Engine wear. Also, it was found that topping up the Oil after a Filter-Only change every 5k mi. refreshed the Oil for another 5k mi. Turns out that the Chronic
every 3,000 miles Oil Changers are actually doing more harm than good to their Engines.
With Modern Oils, a Change has much less to do with the Oil's Lubricating properties than with flushing the Dirt, Acid, and Moisture from the Engine. The Oil is made to trap these things and hold them in suspension. Moisture and Acid are combustion by-products while the Dirt is mainly composed of Carbon and what the Air Filter passed into the Engine. This is why I wouldn't go over 10k mi. - not good to have that stuff floating around.
But, for a Seasonal Car, the Oil should be changed just prior to hibernating the Car for the season. This is because the moisture will evaporate out of the Oil and condense on the Engine Internals causing corrosion and pitting. You should change the Oil and run the Car less than 15 min. before shutting it down. I put no more than 4k mi. on all my Fun Cars during the driving season here in Minnesota before changing it at the end of the season. It kills me to dump all that premium Synthetic Oil, but that's the price of admission...
Happy Motoring!... Jim'99