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Diesel how old is too old?
Posted: 18 Aug 2025, 08:29
by R0B
The fuel in my night heater tank is about 3 years old. Do you think its OK to run the heater? The van has been away for 18 months. And I have not run the heater for a couple of years.
Re: Diesel how old is too old?
Posted: 18 Aug 2025, 09:45
by clift_d
My understanding is that diesel actually has a relatively short shelf life - typically quoted as 6 - 12 months under normal conditions. The big issues are water contamination, which can also lead to diesel bug in the fuel, and degradation of the biodiesel fractions.
Given that it's such a small quantity it might just be best to replace it with fresh.
Re: Diesel how old is too old?
Posted: 18 Aug 2025, 09:56
by Oldiebut goodie
No problem! Nothing to worry about - it isn't a highly tuned racing machine

Any diesel bug should be caught by the filter - highly unlikely to get it in a small tank anyway. I have used 10 year old diesel in heaters!
Re: Diesel how old is too old?
Posted: 18 Aug 2025, 10:03
by R0B
Thanks Rick. That's settled it for me.

Re: Diesel how old is too old?
Posted: 18 Aug 2025, 12:33
by TwinTurbo
Military trucks can sit for years waiting to be good to go.
Our work backup generator has probably used 3 out of 200L of deisel in 12 years and it fires up 1st time each month for gen test.
Re: Diesel how old is too old?
Posted: 18 Aug 2025, 13:36
by davidoft1
Oldest I’ve used was from the 70s on a backup generator, was fine