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Old 03-30-2003, 06:11 PM
Duke2.6 Duke2.6 is offline
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Join Date: Mar 2003
Location: Southern California
Posts: 2,055
Judge motor oil by API service classification, not brand name. For spark igntion engines the most current classification is SL; CI-4 for diesel engines. Though I use CI-4 oil in my pre-converter vintage cars, I do not use it in my modern cars with catalytic converters.

Vintage engines, especially those with carburetors can benefit from the richer additive package of CI-4 oils, but because the combustion byproducts of many of the addtives are not kind to catalytic converters CI-4 oil may shorten converter life, especially on engines with high oil consumption, and modern fuel injected engines do not need as rich an additive package because their more precise fuel metering leads to less fuel dilution in the oil unless the engine has excessive blowby, which probably means it needs major work.

Refer to your owner's manual for proper viscosity ranges based on the highest and lowest ambient temperature the engine will see on a cold start during the period the oil will be in the crankcase.

There can be wide price spreads between SL oils based on rebates and sales, so I buy whatever name brand SL oil is on sale at the time I need a case. Major brand CI-4 oils tend to be priced about the same, and for not particular rational reason, I prefer Chevron Delo.

To learn more about motor and gear oil classifications visit the American Petroleum Institute web site

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