HEAVY DUTY DIESEL ENGINE OIL
Resists Viscosity Loss
Extreme Temperature Protection
Superior Thermal Stability
Low-Ash Formulation
Maximized Engine Protection
Advanced additives fight wear and heat, ensuring shear stability and longer oil life.
Extreme Temperature Protection
Low-temp fluidity ensures fast cold starts and quick lube flow in freezing conditions.
Proven Clean Performance
Oxidation and thermal stability reduce sludge while low-ash chemistry protects DPF systems.
WHAT OIL IS BEST FOR YOUR TRUCK?
15W-40 FULL SYNTHETIC
The classic heavy-duty diesel oil—tough, proven, reliable. Excellent for hot climates, towing, and high-load conditions. Fits most Cummins, Powerstroke, and Duramax setups with no issues.
5W-40 FULL SYNTHETIC
Best for cold climates since it flows better at startup. Go-to pick for modern turbo diesels like Duramax, Powerstroke, and Cummins. Approved by many OEMs for year-round use where cold starts are common.
10W-30 FULL SYNTHETIC
Provides slightly better fuel economy due to lower viscosity. Recommended by Cummins for some medium-duty trucks. Works best in moderate climates, but may not protect as well in high-heat/heavy towing compared to 15W-40.
15W-40 SEMI-SYNTHETIC
Budget-friendly option that still gets the job done. Offers less extreme temperature performance than full synthetic. Great for fleet trucks or regular oil change intervals.
WHAT OIL IS BEST FOR YOUR TRUCK?
15W-40 FULL SYNTHETIC
The classic heavy-duty diesel oil—tough, proven, reliable. Excellent for hot climates, towing, and high-load conditions. Fits most Cummins, Powerstroke, and Duramax setups with no issues.
5W-40 FULL SYNTHETIC
Best for cold climates since it flows better at startup. Go-to pick for modern turbo diesels like Duramax, Powerstroke, and Cummins. Approved by many OEMs for year-round use where cold starts are common.
10W-30 FULL SYNTHETIC
Provides slightly better fuel economy due to lower viscosity. Recommended by Cummins for some medium-duty trucks. Works best in moderate climates, but may not protect as well in high-heat/heavy towing compared to 15W-40.
15W-40 SEMI-SYNTHETIC
Budget-friendly option that still gets the job done. Offers less extreme temperature performance than full synthetic. Great for fleet trucks or regular oil change intervals.
What Your Diesel Deserves
Doc’s Diesel Oils are built to protect hard-working diesel engines, and each formula delivers strong wear protection, low oil consumption, and rock-solid performance in extreme conditions.
What Your Diesel Deserves
Doc’s Diesel Oils are built to protect hard-working diesel engines, and each formula delivers strong wear protection, low oil consumption, and rock-solid performance in extreme conditions.
