Old wives tale!!!

Use a API service category SL oil in a viscosity range recommended in the owners manual for the expected ambient temperarture range until the next oil change.

If the engine is supected of having a "sticky lifter" as evidenced by a ticking noise in the valvetrain use a HD diesel engine oil - API service category CI-4. These oils have a richer detergent, dispersant, anti-wear, and anti-corrosion additive package, however, since the combustion byproducts of some of these additives can degrade catalysts, they are not recommended for continuous use for catalyst equipped cars.

For more info on motor and gear oils visit www.api.org

Duke