WHY MAMMOTH TRUSTS THIS PRODUCT

In the Pacific Northwest, our flying weather changes by the minute. We recommend PHILLIPS 66® X/C® 20W-50 because it’s the ultimate "do-it-all" workhorse for year-round reliability. Before X/C, pilots had to swap between thin winter oils and thick summer grades. This is the Gold Standard that changed everything—offering the rapid cold-start flow of a 20W in the morning and the rock-solid protection of a 50-grade in the heat of the afternoon. We trust it because it has more flight hours behind it than almost any other multi-grade oil on the market, ensuring your engine hits its TBO with internal components that look factory-new.