How Long Can a Generator Sit Without Being Used?
A generator can sit without being used for about a month with petrol in the tank, and far longer if you drain or stabilise the fuel first. Here's the timeline, and what to do at each stage.
Generator Storage Timeline
The clock that matters most is the fuel. Every stage below is really about what the petrol in the tank is doing while the generator waits.
Up to a Month
Westinghouse says fuel stored for as little as 30 days can go bad, leaving gum and varnish in the fuel lines and engine. BP Australia's fuel storage fact sheet agrees: the storage life of petrol in equipment fuel tanks is one month.
Honda goes shorter. Its fuel recommendations say fuel can deteriorate in as little as 15 days depending on where you are, and warm storage and part-full tanks speed it up.
Inside a month, the easy fix is to use it. The Westinghouse iGen2250 manual says run the generator at least once a month for 30 minutes at no less than a third of its load. If that's not going to happen, store it properly.
One to Three Months
For a one to three-month sit, Westinghouse's procedure is to add fuel stabiliser, fill the tank with fresh fuel, then run it for 10 minutes so treated fuel reaches the whole fuel system. Turn it off, shut the fuel cap vent, let it cool and store it somewhere clean and dry.
A full tank matters. Honda says the air in a part-filled tank promotes fuel deterioration.
More Than Three Months
Past three months, Westinghouse drops the stabiliser and empties it instead. Drain the fuel, then run it with no load until it stops on the last of the fuel, and change the engine oil.
Then pull the spark plug, pour a tablespoon of clean engine oil into the hole, turn the engine over a few times with the recoil starter and refit the plug. Finish by pulling slowly until you feel resistance, which leaves the valves closed and helps prevent internal corrosion.
| How long it sits | What Westinghouse says to do |
|---|---|
| Up to a month | Run it once a month for 30 minutes at a third load or more |
| One to three months | Stabiliser, full tank of fresh fuel, run 10 minutes, store clean and dry |
| More than three months | Drain fuel, run dry, change oil, oil the cylinder, store clean and dry |
What Goes Wrong While It Sits
Westinghouse says the most commonly experienced faults with portable generators come down to contaminated or stale fuel. Those faults aren't covered by warranty.
Stale Petrol in the Carburettor
Gum and varnish restrict fuel flow and stop the engine starting. One owner on Whirlpool brought back a little McCulloch 400W generator that hadn't run for years. They found gummy deposits in the tank and carby and a completely blocked main jet, and once those were cleaned it started first pull.
To be fair, owners' luck varies. The owner who started that thread found 18-month-old fuel had turned green in their generator's tank. After mixing in about as much fresh fuel, it started with some mucking around and ran for 50 minutes, and another poster said they'd used five-year-old batches in their generator. The makers don't bet on that, and neither should you when it's needed in a blackout.
Diesel Fuel in Storage
Diesel is more forgiving. BP says it isn't volatile, so it doesn't have petrol's starting and evaporation issues, and sealed under cover it usually lasts a year. The main problem is gums and sediments that can block filters.
Opened containers are the risk. BP says condensation moisture lets fungus and bacteria grow and degrade diesel, and suggests a biocide every six months for long storage.
Flat Batteries on Electric Start
Electric start adds a battery to look after. Westinghouse's manual for its WHXC generators includes steps for charging the starter battery, including with a mains-powered charger, so keep it topped up while the generator sits. Recoil-start models like the Hyundai HY4100L don't have a battery to go flat.
Bringing a Generator Back Into Service
However long it's been, don't just fill it and yank the cord.
Fresh Fuel and an Oil Check
Westinghouse says use only fresh fuel when you bring it out of storage, rather than reusing old fuel. If you oiled the cylinder, it may smoke for a minute or so after starting, and that's normal. Check the oil level too, and see how often generators need oil if it's due.
If it floods or won't catch, what causes a generator to flood covers it.
A Test Run Before Storm Season
Energex says at the start of each storm season, drain the fuel tank and refill it with fresh fuel, check the fuel line for cracks, and run the generator to make sure it works, getting any servicing done then.
So how long can a generator sit without being used? About a month on petrol before you should run it, up to three months with stabiliser, and as long as you like once it's drained and prepared. Where to put it while it waits is in where to keep a generator when not in use, and cold-weather prep is in how to winterise a generator.
Need one that's easy to live with between uses? The generator finder helps, or talk to us on 03 7056 6732, or SMS 0476 330 590.
