If your RV has a generator on board, that small engine is one of the most important—and most overlooked—components keeping your adventures powered. From running your air conditioner to brewing your morning coffee off-grid, the generator makes life on the road possible. But like any engine, it needs regular care to stay reliable.
In this guide, we’ll walk through how to properly check your RV generator’s oil—and when to do it—based on lessons from Chris Archibald, instructor at the National RV Training Academy (NRVTA) in Athens, Texas. Chris teaches the advanced generator course at NRVTA, where students learn to diagnose, repair, and maintain generators for all types of RVs.
Why Checking Your Generator Oil Matters
Neglecting to check your oil can lead to catastrophic engine damage. Inside your generator, the oil lubricates moving parts and keeps the engine from overheating. If the oil level drops too low—or becomes contaminated—the metal components inside can grind together, leading to costly repairs or a complete engine failure.
Your owner’s manual will tell you exactly how often to check, but as Chris points out, most Onan generators recommend checking oil every 8 hours of run time. For diesel generators, it’s typically every day of use.
Step-by-Step: Checking Oil on a Gasoline RV Generator
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Access the Generator
Most RV generators are tucked behind a compartment door on the exterior of the RV. Open the cover to expose the generator housing. -
Locate the Dipstick
You’ll usually find it under a yellow cap. Before touching anything, make sure the generator is turned off and cool to the touch. -
Remove and Clean the Dipstick
Have a clean rag ready to prevent drips. Remove the dipstick, wipe it clean, then reinsert it fully threaded in before pulling it back out to check the level. -
Read the Oil Level
The oil should be between the “Add” and “Full” marks—ideally about three-quarters of the way up. -
Watch for Signs of Contamination
If the dipstick shows overfilled oil or you notice a gasoline smell, it could indicate fuel is leaking into the oil. This is a serious issue that prevents the oil from properly protecting your engine. 🚫 Do not run the generator if you suspect fuel contamination.
Call a qualified RV technician to drain the oil and diagnose the source of the problem. -
Safety Reminder
Gasoline-contaminated oil is more flammable than normal, so keep open flames—like cigarettes or campfires—far away from the area.
How to Check Oil on a Diesel Generator
Diesel models, commonly found in larger motorhomes, follow the same principles but may look a bit different.
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Open the Side Panel
Unlatch and remove the generator’s side cover. Place it securely nearby so it doesn’t fall or get damaged. -
Find the Dipstick
Don’t confuse the oil fill cap with the dipstick—they’re often separate. The dipstick will usually be off to one side. -
Wipe, Insert, and Read
Just like before, use a clean rag to wipe the dipstick, reinsert it, and check the level. -
Inspect the Oil’s Condition
The oil should be clean and amber in color. If it’s dark, gritty, or smells unusual, it may be time for a change. -
Use a Clean Rag
Dirt or sand on your rag can easily find its way into the engine, leading to internal wear. Always wipe the dipstick with a lint-free cloth.
When and Why Consistency Counts
Whether your generator runs on gasoline or diesel, checking oil regularly keeps it running smoother and longer. A quick inspection before a weekend trip—or after a long day of running the A/C—can help you spot issues before they turn serious.
As Chris reminds his students:
“If you want to keep your generator running well for a long time, checking your oil when you’re supposed to and keeping it full is one of the simplest and most important things you can do.”
Want to Learn More?
If you’re the kind of RVer who loves to understand how things work, you can learn the same hands-on techniques taught in this video at the National RV Training Academy. NRVTA offers training programs for RV owners, technicians, and inspectors—helping people start businesses, earn income while traveling, and keep fellow campers safe.
Visit NRVTA.com to learn more about courses and upcoming training opportunities.
Final Tip:
A generator that’s properly maintained is a generator that’s ready when you need it most. Keep that oil checked, stay safe, and enjoy the open road!