Mobil Delvac Extreme is formulated with synthetic basestocks and a boosted additive system tailored to deliver extended performance for up to two times beyond OEM recommended oil drain intervals. The proprietary formulation delivers excellent wear protection, exceptional oxidation stability, and outstanding TBN retention. Mobil Delvac Extreme also provides outstanding resistance to oil consumption, oxidation, corrosive and abrasive wear, and high temperature deposits. Mobil Delvac™ Extreme 15W-40 is a synthetic, high-performance diesel engine oil that helps extend engine life while providing long drain capability for modern diesel engines operating in extreme conditions.