Question about oil analysis

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SC
If you're going to do an oil analysis, and you've just switched brands of oil, wouldn't it be better to do the analysis after you've changed the oil twice? The first batch is still going to have some of the old brand in it, albeit a small amount. (And if you've been using an inferior oil before, the results could be skewed because of deposits that the new oil would be cleaning out on the first go-round.) The main reason I'm asking is that someone posted in my thread about my switching to Rotella T Synthetic asking if I was going to do an analysis. I probably am, but I'm going to wait until I've changed the oil again and then do it on that batch.
 

Patman

Staff member
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Guelph, Ontario
You should still do an analysis just for curiosity, but in reality it's not a 100% true report since like you said there is still some of the old oil mixed in there. You will still see a difference in the wear metals though, it's just that with the slight additive clash that could be possible, the first fill with the new oil might show higher oxidation than it will on the subsequent fills. The TBN might drop faster on the first fill as well. I'd still do the analysis just for curiosity though (which is exactly what I'm doing this weekend, I'll be draining out my first fill of Schaeffer 10w30 blend at 4300 miles, and the last fill was with Maxlife 10w30)
 

MolaKule

Staff member
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Iowegia - USA
XHVI, I would agree that would be the best route to follow unless you're testing lubricants. In the case of testing, I would purge the system with a flush like Neutra #131 or LC (in the flush concentration) and then proceed. [ December 03, 2002, 03:12 PM: Message edited by: MolaKule ]
 
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3,845
We flush with Auto-RX between tests, I agree LC or 131 could be used but I haven't yet. I used to use a SA grade 20w motor oil to clear out previous tested oils. Plated Moly and other "trick polymers" are a different story and will affect the subsequent testing. If the analyst is aware of the previous brand used and is communicating closely with you on the data, that can help in properly associating the reasons for the results. Interpretation is 90% a accurate test procedure.
 

mph

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356
Location
Johnstown, PA
quote:
Originally posted by XHVI: If you're going to do an oil analysis, and you've just switched brands of oil, wouldn't it be better to do the analysis after you've changed the oil twice?
Sure, and you're not supposed to shake the presents before Christmas! But human nature being what it is....
 
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