Thread: Fuel storage lifespan.

Petrol will go off after a couple of months, even sooner, but diesel can last for yonks. We used to test diesel samples from standby generator storage tanks that in some cases were 20 years old. Apart from it looking very dark and oily, if water hadn't got into it, samples sent to the lab came back fine. Usually the old tanks in the basement of multi story buildings were fine, but tanks that were close to the surface - like servo tanks, etc would get condensation into them over time which usually resulted in shorter lived fuel

Petrol expands and compresses with the temperature being hot or cold if you seal your tank it will expand in the warmer weather and passably expanding your tank and warp it or it could cave it in if it turns cold after a hot day so dont seal the tank the breather is there this reason

Breather holes on boat fuel tanks are comparatively small and usually at the end of a long hose. Therefore evaporation rates are low.

Having a breather or not won't affect storage life. As mentioned - the breather is useful to make sure the tank doesn't overpressurise in hot weather.

My ancient Honda powered mower hasn't been used for two years, I added some 1 year old petrol I had in a sealed jerry and it started on the second pull and mowed the front half of my block without stopping. So yeah, petrol may go off but not as fast as you think.

I had to pull the fuel tank and the carby off one of our old mowers that hadn't been used for several years, could be almost 8-10 years! The fuel had dried up and turned into a varnish like goo and blocked up the jets etc. didn't take long to get it all cleaned up with petrol then refilled the tank with new juice and away she went!

Cheers, Mick.

Thanks for the replies but I might have shortened the question a bit too much. I mainly use 95 octane and the boat sits for up to 4 months so my question is, How long do you reckon the fuel should stay good for ?. The tank is under the floor and the boat has a cover so it doesn't cop direct sunlight.

Thanks,
Anthony.

Originally Posted by Stuck

Thanks for the replies but I might have shortened the question a bit too much. I mainly use 95 octane and the boat sits for up to 4 months so my question is, How long do you reckon the fuel should stay good for ?. The tank is under the floor and the boat has a cover so it doesn't cop direct sunlight.

Thanks,
Anthony.

Is your boat tank sealed when not in use, or is it permanently vented? Fuel hasn't got a "use-by date" as such, it all depends on the storage. Sealed cool storage fuel should last for 12 months or more. A full tank is better than a half empty one. Letting the lighter components evaporate by leaving the vent open will shorten its life. Water vapour enters permanently open fuel tanks. If in doubt fit a water trap to your fuel line.

So yeah, it depends. If it starts and runs it's probably OK.

Petrol used to last a lot longer in storage than it does nowadays, not sure what the exact difference is.

You can get additives (StaBil) etc. to extend the storage life of petrol but 4 months shouldn't be a problem.

www.opalfuel.com.au/assets/content/pdf/211293_BP_Opal_FS_StorageHandling_A3.pdf

www.bp.com/retail/liveassets/bp_internet/retail_new/retail_new_australia/STAGING/local_assets/downloads_pdfs/0_999/Petrol_Life_in_vehicle_tanksv4.pdf

You might have to manually cut & paste the above links.

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Colin