How long does synthetic engine oil keep before degrading?

[firewalker]

Might be a daft question but could you buy a 20L drum of 5w 30 Fully Synthetic oil, use part of it for an oil change one year then the rest the next?
I read that it keeps for about 7 years if stored correctly, but what does stored correctly mean?
Does it degrade once opened? If so at what point does it become unusable?

Also, how do you know when the oil was produced and the shelf life begins so you're not putting degraded crap oil in next time?

Finally! On a light use vehicle where mileage will take years to reach the oil change interval how long should you leave fully synthetic oil in your engine before draining it?

I've been using Castrol Magnatec, Ford or Stop/Start for a few years but seeing cheaper options out there. Any recommendations?

2.4 RWD Mk6 LWB HR on 120k miles.

[metalworker0]

Don't know -- heard the additives may sink to the bottom or rise to the top ..so worth rolling it around a bit before you pour some out.

all the best.mark

[andz327]

Would stick with castrol Magnatec A5

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[metalworker0]

You asked - how long should you keep it in the engine ?

That depends on how long or short the journeys you are making are and if they are winter journeys.

Say for instance ..you just went to town every day and it was only 3 miles away ..you would need to change the oil every year, you would be knocking up 2190 miles,
and because the engine would not reach operating temperature for a good amount of time..that's bad for the oil..

if you went on a run over over 20 miles for each journey ...then you could leave it in for longer, but that would be journeys less frequent say 50 journeys of 20 miles or more ...then you could probably change the oil at 3 years.

all the best.mark

[dumper]

I changed mine at 6000 max or before every mot even with Covid it only did 2782 miles still had a change but at 16 months my camper doesn’t do many short runs .

[Altransit]

I've always changed mine every year, or 6000miles at most, but I've never bothered about expensive, branded oils. It's personal choice really.

[firewalker]

You asked - how long should you keep it in the engine ?

That depends on how long or short the journeys you are making are and if they are winter journeys.

Say for instance ..you just went to town every day and it was only 3 miles away ..you would need to change the oil every year, you would be knocking up 2190 miles,
and because the engine would not reach operating temperature for a good amount of time..that's bad for the oil..

if you went on a run over over 20 miles for each journey ...then you could leave it in for longer, but that would be journeys less frequent say 50 journeys of 20 miles or more ...then you could probably change the oil at 3 years.

all the best.mark

Thanks that clears up whether it's just mileage not age that sets the intervals.
It pretty much does 200 miles runs a dozen times a year, a few less but still over 50 miles and never in winter, The only short run is 5 miles to the MoT station or the fuel stop before the long hauls. Annual mileage roughly 3-4k . Oil gets changed once a year but not necessarily at 12 months, could be 15-18 months but your answer leaves me comfortable with that cheers.

[firewalker]

I changed mine at 6000 max or before every mot even with Covid it only did 2782 miles still had a change but at 16 months my camper doesn’t do many short runs .

Mine only does about 3000 a year anyway and can also be about 16 months before a change.