A portable generator needs a fuel and oil check after every run, an oil change at 25 to 50 hours, a new air filter and spark plug around 100 hours, and a full valve-clearance and carburettor service at 200 hours or once a season, whichever comes first. Skip that schedule and the failure shows up exactly when you need the generator most: a stale carburettor that will not prime during the first cold snap, or a rod knock from oil nobody checked. None of this is difficult. It is mostly cheap parts and twenty minutes, done on a schedule rather than when something already sounds wrong.
After every use
Let the engine run under a light load for a few minutes before you shut it off, so the carburettor bowl empties and the engine does not sit with fuel pooled inside it. Check the oil level while the engine is warm but off. Wipe down the housing and check the air filter for dust, especially if you ran the generator on a jobsite or in dry conditions. Let the unit cool fully before you cover it or move it into a shed, since a hot muffler near fuel vapour or dry leaves is how storage fires start.
The hour-based schedule
Most air-cooled portable and inverter generators follow a version of this table. Check your manual for the exact numbers, since larger dual-fuel and whole-house units sometimes stretch the intervals, but this is the baseline nearly every small engine manufacturer publishes.
| Interval | Task |
|---|---|
| Every use | Check oil level, check fuel, inspect for leaks |
| 25 hours | First oil change (break-in), clean air filter |
| 50 hours | Oil change, air filter check, clean spark arrestor screen |
| 100 hours | Oil change, replace air filter, replace spark plug, check fuel filter |
| 200 hours | Valve clearance check, carburettor inspection, fuel line inspection |
| Annually | Full service even if hours are low, since fuel varnish and rubber degrade on a calendar, not just a clock |
That last row matters more than most owners assume. A generator that sat idle all year but only logged eight running hours still needs the annual pass, because ethanol-blended fuel and rubber fuel lines degrade with time, not just use.
Oil, air filter and spark plug
Small engines are unforgiving of the wrong oil. Most air-cooled generator engines specify SAE 30 or 10W-30 in a conventional or synthetic blend, with 5W-30 recommended below freezing for easier starting. Check the dipstick, do not fill by guessing, and change the oil while it is warm so the old oil carries contaminants out with it rather than settling. The first change at 25 hours matters because break-in wear leaves metal particles in that initial fill; skipping it is the single most common reason small engines wear out early.
A dirty air filter is the most common cause of a generator that runs rough or will not hold a steady RPM under load, because it forces the carburettor to run rich. A foam filter can be washed in warm soapy water, dried, and lightly re-oiled; a paper element should just be replaced at the 100-hour mark, or sooner if you are running the generator somewhere dusty. The spark plug should be gapped to the manufacturer’s spec and swapped at 100 hours regardless of how it looks, since a plug that fires inconsistently under load is very hard to diagnose from the outside.
Fuel, ethanol and the carburettor drain
Ethanol-blended petrol is the single biggest cause of small-engine failure in equipment that sits between uses. Ethanol absorbs moisture from the air, and that water-fuel mixture corrodes carburettor jets and gums up as it evaporates, leaving a hard varnish behind. Two habits prevent nearly all of it. First, add a fuel stabiliser to any tank of fuel that will sit for more than about 30 days, at the ratio printed on the bottle, and run the engine for a few minutes afterward so treated fuel reaches the carburettor. Second, for storage longer than a season, drain the carburettor bowl entirely rather than relying on stabiliser alone: run the engine dry, or use the carburettor’s drain screw if it has one. An empty carburettor cannot varnish.
If your generator has sat for a year or more without stabilised fuel and will not start, the carburettor is the first suspect, not the engine. A stuck float needle or a clogged jet from dried ethanol residue is a far more common cause of a no-start than anything mechanical, and it is usually a cleaning job rather than a replacement.
The monthly exercise run
A generator that only runs during outages is the one most likely to fail during an outage. Start it monthly, under a real load if you can put one on it, for 15 to 20 minutes. This keeps the carburettor wet, exercises the seals, confirms the battery holds charge on an electric-start unit, and gives you a chance to catch a failing part while it is an inconvenience rather than an emergency. If you cannot remember the last time it ran, that is the strongest possible reason to run it today, before you need it.
Seasonal and long-term storage prep
Before storing a generator for winter or for an off-season stretch, work through a short list: stabilise or drain the fuel, change the oil so the engine does not sit with combustion byproducts in it, clean or replace the air filter, disconnect the battery on electric-start models to stop parasitic drain, and store the unit somewhere dry with the fuel valve off. A silica gel pack or moisture absorber near the unit helps in a damp shed or garage. Coming out of storage, do not just pull the cord; check the oil, check the fuel, and inspect the fuel lines for cracking before the first start of the season.
Valve clearance
This is the maintenance step owners skip most often because it needs a feeler gauge and a bit of patience rather than a five-minute job. Valve clearance that drifts out of spec shows up as hard starting, a rough idle, or a gradual loss of power, and it is worth checking at the 200-hour mark or annually on a generator that gets regular use. It is not urgent in the way an oil change is, but ignoring it for years is how a generator ends up needing a valve job instead of an adjustment.
The honest comparison: what a battery power station skips entirely
None of the schedule above applies to a battery-based power station. There is no oil, no air filter, no spark plug, no carburettor to gum up with ethanol, and no monthly exercise run required to keep it ready. You plug it in, or leave it on a trickle charge, and it works when the power goes out. That is a genuine part of the cost comparison between the two, not just a footnote: a generator that needs an annual service, an oil change every 50 hours, and periodic parts has an ongoing cost a power station simply does not, and it is worth weighing against the sticker price alone. See the power station price index for what that upfront cost actually buys across the current catalogue, and home battery backup for how a stationary or portable battery system compares to a generator for whole-home use.
The trade-off runs the other way too. A power station like the BLUETTI AC180 Portable Power Station, at roughly 1,150Wh and about 1,800W of continuous output for $449, has no maintenance schedule at all, but it also has a fixed capacity: once it is empty, it is empty until you recharge it, while a generator with a full fuel can keeps running for as long as you keep feeding it petrol. If you are sizing either option against your actual appliances, start with the appliance wattage chart or, for the single highest-draw item in most homes, watts to run a refrigerator, and use the watts-to-amps calculator to check what a circuit can actually carry before you commit to either kind of backup power. For a fuel-free comparison, how a solar generator works covers the charging side of the equation a fuel generator does not need to think about at all.
Neither machine is the wrong answer. A generator with a properly kept schedule is reliable, refuels in minutes, and scales to whatever load you put on it. A power station trades that flexibility for zero maintenance and silent, fume-free operation. The maintenance list above is the real cost of choosing the generator, and it is worth reading in full before you decide you have the time for it.
How this page makes money. Some links here are affiliate links and we earn a commission if you buy through them — currently BLUETTI, ALLPOWERS, Mango Power, Renogy and MoonCool. Every other brand on this page is here because leaving it out would make the comparison useless to you, and we are paid nothing either way. Prices are each maker’s own list price at the time of writing and change often.