RV Generator Maintenance: Run Hours, Oil Changes, and Keeping Your Power Reliable

The generator is the part of your rig you don't think about until the moment it won't start. You're boondocked somewhere with no hookups, the batteries are low, you push the button, and nothing happens. Generator maintenance is the kind of thing that's invisible right up until it's the only thing that matters.

The good news is that keeping an RV generator reliable isn't complicated. But it does mean understanding one thing that's different from how you maintain the rest of your rig: generators run on run hours, not calendar time. And what you actually need to do depends on which kind of generator you've got. Get those two ideas straight and the rest follows.

Run hours: the concept that changes everything

Most of your RV maintenance runs on a calendar. You winterize in fall, you inspect the roof seasonally, you flush the water heater once a year. The generator doesn't work that way. A generator's wear is measured by how many hours it has actually run, not by how much time has passed on the calendar.

This is the single most important idea in generator maintenance, and it's the one most owners get wrong. A generator that ran for 200 hours in six months needs more attention than one that ran 40 hours in two years, even though the second one is older. The engine doesn't care what month it is. It cares how long it's been turning.

Your generator has an hour meter that tracks total run time, usually on the generator control panel or readable through your RV's monitor system. That number is the one that drives your maintenance schedule. When a manufacturer says to change the oil every 150 hours, they mean 150 run hours on that meter, whenever that happens to land on the calendar.

There's one calendar-based exception worth knowing, and it cuts the other way: a generator that sits unused for long stretches also needs attention, not because of run hours but because of what happens to fuel and seals when an engine sits. Stale fuel, dried-out seals, and moisture are the enemies of a generator in storage. So the rule is really two rules. Maintain on run hours when you're using it, and exercise it regularly when you're not. More on the storage side later.

Know what kind of generator you have

What you actually do for maintenance depends on the type of generator in your rig, and there are a few distinctions that matter.

The most common built-in RV generator is an Onan, now branded under Cummins, which powers the majority of motorhomes with factory-installed generators. Built-in generators are permanently mounted, draw from your rig's main fuel supply, and are sized to run rooftop air conditioning and household loads. If you've got a Class A or larger Class C motorhome, you very likely have a built-in Onan or similar.

Portable inverter generators are a different category. These are the units many travel trailer and smaller RV owners carry and set up outside the rig, brands like Honda, Yamaha, Champion, and others. They've got their own fuel tanks, they're maintained much like a small engine, and they get moved, stored, and handled differently from a built-in unit.

Underneath the built-in versus portable distinction is the fuel type, and this matters as much as anything for maintenance. RV generators run on gas, propane, or diesel, and each has different maintenance needs. Gas generators need spark plugs and are vulnerable to stale fuel and ethanol problems. Propane generators burn cleaner and don't have fuel-stabilizer concerns, but they need regulator and hose attention. Diesel generators have the longest service life and different intervals, but they require diesel-specific fuel system care.

Knowing your exact generator, the brand, the model, and the fuel type, is the starting point for everything below, because the intervals and the specific tasks vary by unit. The numbers in this article are the generally accepted ranges across the industry, but your generator's own manual is always the authority for your specific unit. Manufacturer documentation, such as the official Cummins Onan operator manuals, lays out the exact periodic maintenance schedule for each model.

The core maintenance tasks

These are the tasks that apply across most RV generators, with the typical intervals. Treat the intervals as a starting point and let your owner's manual override them, because they vary by make, model, and fuel type.

Oil and oil filter changes

Oil changes are the single most important generator maintenance task, the same way they are for any engine. Running a generator on old or low oil is the fastest way to destroy it.

There's one interval specific to a new or newly-acquired generator worth knowing: the first oil change comes early, often at 20 to 50 run hours depending on the model, to clear out the metal particles from the initial engine break-in. This first change is more important than people realize, and it's easy to blow past it if you boondock heavily early on. After the break-in change, the typical interval is every 100 to 150 run hours or once a year, whichever comes first, though some diesel units run longer intervals and your manual sets the real number for your unit.

The oil filter gets changed with the oil on most units. On many built-in generators the oil change is genuinely easy, with accessible drain and fill points behind the access panel. On others it's more awkward, which is part of why some owners have a shop handle it.

Air filter

The air filter keeps dust and debris out of the engine. A clogged air filter restricts airflow, makes the generator run rich and rough, and over time hurts performance and engine life. Inspect the air filter regularly and replace it on the manufacturer's schedule, and more often if you run the generator in dusty conditions, which clog it a lot faster. Boondocking in the desert is hard on air filters.

Spark plugs

Gas generators have spark plugs that wear and foul over time and need periodic replacement and gap inspection. Propane and diesel generators have different ignition arrangements, so this task is specific to gas units. The replacement interval is on the longer side, but a fouled or worn plug causes hard starting and rough running, so it's worth keeping on the schedule your manual specifies.

Fuel filter

The fuel filter keeps contaminants out of the fuel system. It gets changed less often than oil, commonly every 500 hours or every two years, but a clogged fuel filter makes the generator starve, run poorly, or stall under load. Diesel units in particular benefit from attentive fuel filter and water separator maintenance.

Running under load

This one isn't a repair task but a maintenance habit, and it matters more than most owners realize. Generators are built to run under load, and they suffer when they sit unused or only ever run at light loads. Most manufacturers recommend exercising the generator at least once a month, running it under a real load of around 50 percent of its capacity for a sustained period. For a 4,000 watt generator, that means putting roughly 2,000 watts of load on it, which you can do by running the air conditioning and a few appliances together.

Exercising the generator monthly keeps the seals lubricated, burns off moisture, keeps fuel from going stale in the system, and surfaces problems while you're at home rather than at a campsite. It's the single best habit for generator longevity, and it costs nothing but the fuel.

Type-specific notes

Beyond the common tasks, each generator type has its own particular needs.

Diesel generators tend to have the longest service life of the three fuel types, often lasting many thousands of run hours, but they need careful fuel system maintenance. Water in the fuel is a diesel engine's enemy, so the water separator needs regular draining, and the fuel filters need attention on schedule. Diesel also benefits from being run under load regularly, since light-load running over time can cause a condition called wet stacking that fouls the engine.

Propane generators burn the cleanest of the three. They don't have carburetor varnish problems, stale fuel concerns, or spark plug fouling from rich gas mixtures, which makes them low-maintenance in some respects. What they do need is attention to the propane delivery system: the regulator, the hoses, and the fittings should be inspected for wear and leaks, since a propane leak is a safety issue, not just a performance one.

Portable inverter generators are maintained much like any small engine, with oil changes, air filter service, and spark plug replacement on the manufacturer's schedule. Because they get moved and stored more than built-in units, the storage and fuel considerations below are especially relevant for them.

Gas generators are the most vulnerable to fuel problems, which brings us to storage.

Storage and the fuel problem

If a generator fails after sitting unused, stale fuel is almost always the reason. Gasoline starts to degrade in a matter of weeks to months, and modern fuel containing ethanol is worse, because ethanol attracts moisture and can gum up the carburetor with varnish that keeps the generator from starting. Once ethanol absorbs enough water it separates out and settles in the fuel system, and the result is often a carburetor fouled with corrosion.

For gas generators going into storage, you've got a few options. You can add a fuel stabilizer to fresh fuel and run the generator long enough to circulate the treated fuel through the system, which is the most common approach. You can run the carburetor dry by shutting off the fuel supply and letting the generator run until it stops, which leaves no fuel in the carburetor to varnish. Or you can drain the fuel system entirely for long-term storage. Your manual will recommend the right approach for your unit.

Propane generators don't have the stale fuel problem, since propane stores indefinitely, which is one of their genuine advantages for RVs that sit between trips. Diesel stores better than gasoline but still benefits from a stabilizer and from keeping the tank full to cut down on condensation during long storage.

The best storage practice of all, across every fuel type, is the monthly exercise habit. A generator that gets run under load once a month rarely develops storage problems in the first place, because the fuel never sits long enough to go stale and the engine never sits long enough to seize up seals. If you do nothing else for your generator, run it monthly.

A word on safety: carbon monoxide and ventilation

Generator maintenance isn't only about reliability. It's also about safety, and the safety issue with generators is carbon monoxide.

A generator's exhaust contains carbon monoxide, an odorless, colorless gas that can kill without warning. Every RV with a generator should have working carbon monoxide detectors, and testing them is part of responsible generator ownership. Never run a generator in an enclosed or poorly ventilated space, and pay attention to where the exhaust goes, including the wind blowing it back toward open windows or into a neighbor's site.

Part of generator maintenance is confirming that the exhaust system is intact and that ventilation around a built-in unit is clear. A damaged exhaust or a blocked ventilation path is a genuine hazard, not just a performance problem. If you ever smell exhaust inside the rig while the generator runs, or your CO detector goes off, shut the generator down and deal with it before running it again.

How RVKeeper tracks it

The hardest part of generator maintenance isn't the work. It's remembering that the generator runs on run hours, keeping track of where those hours stand, and knowing when each service is actually due for your specific unit.

That's exactly what RVKeeper is built to handle. You log your generator, its type, and its current run hours, and RVKeeper tracks the service intervals that apply to your unit, the oil changes, the filters, the spark plugs, against the hours you actually put on it rather than a generic calendar. An Onan diesel and a portable gas inverter don't get the same schedule, and RVKeeper builds the right one for what you actually own. It works alongside your complete RV maintenance checklist so the generator doesn't become the one system that slips through the cracks.

The Essentials plan is free, no account or card required.