Used oil shelf life (for testing)?

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Sep 26, 2002
If I saved a sample of my used oil for later testing: 1. would the oil's chemistry change from sitting? 2. if yes to #1, how long could it sit? 3. how much of a sample is needed for testing? Thanks
Have it analyzed early if you can. The older the sample the greater the uncertainties. Results don't age. [Wink] That said, keep it in the dark and keep the temperature cool & stable. Using a non-leachable container would also help. I have a couple samples in canning jars waiting for $8 kits. David
I draw 6 oz samples on the average. Some labs like six, some four. I believe 4 oz. is the minimum. Maybe Terry Dyson has a preference.
Your highest risk from sitting is evaporation of fuel contamination, so it is a good idea to send relatively soon after draining. I send samples to my Lab on the 1st of the month and somewhere in the middle of the month. Anything that gets to me on the 2nd waits a couple of weeks. For Engine tests I always send about 100 ml. and keep another 100ml as a counter-sample in case anything happens.
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