HEAVY DUTY DIESEL ENGINE OIL
Resists Viscosity Loss
Extreme Temperature Protection
Superior Thermal Stability
Low-Ash Formulation
Maximized Engine Protection
Fights thermal breakdown and sludge while maintaining shear stability to protect parts and extend oil life.
Extreme Temperature Protection
Flows fast in freezing temps for reliable cold starts when the job won’t wait.
Proven Clean Performance
Oxidation control helps cut deposits and keeps internal parts running cleaner.
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.
