An oil analysis report showed that the Amsoil XL 5W-30 did not need changing after 13,000 kms. and 7 months of drivng in the '02 Sunfire. Information on Amsoil synthetic lubricants and related filters can be seen at
Smells like it too!
They used to have a 100,000 mile set up too. Uses oil analysis, but may be too complicated for some people. They did an analysis every 25K, changed spin on filter then, but not the canister filter nor the oil.
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