Used oil shelf life (for testing)?

[vtr1000]

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

 

[OneQuartLow]

Have it analyzed early if you can. The older the sample the greater the uncertainties. Results don't age. 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

 

[MolaKule]

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.

 

[widman]

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.