So i'm close to startig a xflow engine thats not started for 15 years. I was thinking i should change the oil before i try starting it (*). I've got some cheap 20w50 oil (cheap as in ASDA smart price cheap) from 15 years ago. Its not easy to get more oil at the moment and the engine is just going to be used to setup electronic ignition and hopefully fuel injection whilst in the garage.

Will the ASDA oil be ok for a few start ups or does oil go off? i've got 5l still sealed and about 1l in a 5 litre container.

(*) Prior to being put away the engine had an oil change and then only did a few hundred miles along with some periodic start ups to get the engine up to temperature and battery charged. Once put away the engine had every 3 to 6 months WD40 or occasionally oil added to the bores and turned over by hand - although that stopped 5 to 7 years ago. Turning over now its free, you feel compression and a hiss when the exhaust valve opens. (mentioning this so someone will reassure me its fine to run for a few start ups without an oil change).

Oil in a sealed container isn’t likely to deteriorate, chances are the oil in the engine would be OK but it would pay to prime the oil pump as any oil that was in it may have drained. I used some cheap 20/50 for running my engine in before changing to Millers 20/40 , not really sure about changing to something like 10/40 semi synthetic but might give it a try

If the oil that's in it has been used, especially on short runs 'up to temp' (*) then drain it.

It will be contaminated with water etc. However for a short run to see if it works then there isn't much harm. Once you know it runs, drain it and fill with fresh.

* most 'up to temp' runs are anything but. While water temp might show fully hot, the oil temps rarely are and they aren't long enough to boil off any water vapour/condensation which builds up over the course of these 'short' runs.

[Edited on 28/4/20 by flak monkey]

Yes for £10 worth of oil I'd change it and I'm a proper skinflint with oil!

I for many years used cheap asda 20/50 oil to do intial startups and running in, and all on my xflows, and once I hit a couple of hundred miles put in Millers 20/50 and gave the engine a good thrashing

the oil in the engine now is not ok to use, to much water content

The mineral oil in the lotus is about ten million years old. Runs fine.