15W-40 Oils
Our 15W-40 engine oils. Your handbook gives the grade and specification your engine needs.
Diesel Gard 15W-40 CI-4
A premium mineral-based heavy-duty diesel engine oil formulated to deliver reliable performance in turbocharged and naturally aspirated engines.
Diesel Gard SE 15W-40 CI-4
A shear stable high-quality mineral engine oil for high output, high-speed diesel engines.
Fleetmaster 15W-40 CH-4
A mineral engine oil designed to lubricate and protect high-speed diesel engines.
What 15W-40 means
15W-40 is an SAE viscosity grade. The first number, followed by W for winter, shows how easily the oil flows when cold: the lower the number, the faster it reaches the engine at start-up. The second number shows how thick the oil stays at normal running temperature: the higher the number, the thicker the oil.
So a 15W-40 flows more easily from cold than a 20W-40, and is thinner when hot than a 15W-50.
Use a grade your car's manufacturer lists, with the specification it asks for as well: oils of the same grade can meet different specifications.
More in our guide to what the numbers on engine oil mean.