MOBIL DELVAC 1 GEAR OIL 75W-90 Mobil Delvac 1 Gear Oil 75W-90 is a fully synthetic drivetrain lubricant engineered to meet very demanding extended drain and warranty requirements. Mobil Delvac Syn Gear Oil 75W-90 Mobil Synthetic Gear Oil 75W-90 is a fully synthetic gear lubricant formulated from synthetic base oils and an advanced additive system. Mobil Synthetic Gear Oil 75W-90 Mobil Synthetic Gear Oil 75W-90 is a fully synthetic gear lubricant formulated from synthetic base oils and an advanced additive system.