How Often Should I Change My Lube Oils?

Helpful guide to keeping your engine running strong - Tech Tip #71

This Tech Tip is one in a series we publish to help owners of Perkins diesel, John Deere, Deutz, Cummins and other engines have a more trouble free ownership experience. This Tech Tip is oriented toward the marine auxiliary engine and diesel generator owner who uses his boat only seasonally.

How Often Should I Change My Engine Oil?

The long answer is to consult your owner's manual, check your hour meter, etc. The short answer is to change the engine oil every 100 hours, which equates to once a season. (One way to think about this is that 100 hours of use at the marine equivalent of 50 miles an hour is equivalent to 5000 miles, a common passenger car oil change oil interval.) If you use your engine as prime power and not as an auxiliary engine or generator you should change it twice a season or even more frequently.

How Often Should I Change The Oil in My Marine Transmission?

Again, the long answer is to hide behind the admonishment to check the owner's manual for your specific marine transmission brand (e.g., ZF/Hurth, Twin Disc®, Borg Warner, etc.), check the hour meter (often broken), and so on. The more helpful short answer is to change the oil in your marine gear every other season. This is consistent with most manufacturers’ requirements to change it every 250 hours. (If you need a Workshop Manual for a Hurth, Borg Warner Or Paragon, we have these manuals ready to ship. Please call us at 800-233-6539 to order).

When Should I Change the Oils?

Change the oils in the fall when you come out of the water for the season. This way you avoid having dirty, moisture laden, and corrosive oil in your engine or gearbox over the long winter. See Tech Tip #33 Disposing of used Lube Oil for some handy tips on what to do with the old oil.

Which Lube Oil Lubes Should I Use?

In earlier Tech Tip #1 Blend the Oil in a Perkins Marine Diesel and Tech Tip #4 Adventures in Oil as well as Tech Tip #23 Oil Filters: Capacity Counts and Tech Tip #25 Break in Oil: Not Synthetic we discuss various grades of engine oil and suggest a 50/50 mixture of Shell Rotella/Mobil1. We still stand behind that. For marine transmissions, it is important to check the plate put on the transmission by the manufacturer. Hurth Marine transmissions use different fluids depending upon if they are mechanical transmissions (e.g., the ZF/Hurth 50, ZF/Hurth 100, ZF/Hurth 150 etc.) or hydraulic transmissions (e.g., ZF63A, etc.) Borg Warner Velvet Drive transmissions use gear oil.

How Much Gear Oil Should I Use?

See Tech Tip #78 Hurth Transmissions: The Ins and Outs of Basic Service for the specific quantities your Hurth transmission Requires. For other gears, consult your owners manual.

We hope this Tech Tip is helpful. Please call us with any questions. Foley is different: we’re a 90 year old family firm that wants to help!


Manufacturers names, symbols and numbers are for reference purposes only and do not imply manufacturing origin.

We take tech support seriously!

We hope that you will find this Tech Tip helpful. We believe that Tech Support matters and welcome your comments or suggestions.

Please email Dr. Diesel™ using our contact form or call us at 800.233.6539.