The secret is out.
Big oil makes big money on conventional motor oils and short drain intervals.
For more articles please use the navigation menu. Automotive Lubrication Online Discussion Forum Conventional oil companies speculate that synthetics can't provide extended drains, due to additive loss and combustion by-product contamination. They haven't done research to back their claims. In conventional oils, oxidation inhibitors deplete quickly, due to the rapid oxidation of petroleum basestocks. Viscosity loss leaves oils incapable of protecting engines from metal to metal contact and wear in high temperatures.