Actually it does affect the ftirs reading and will cause it to read high BUT.... here is the kicker.. You can get a proper oxidation level reading from redline. OK, lets look at this and explain.
These ftir machines have to have a baseline to go by, meaning if you are going to see how high oxidation levels are on one oil it must know where the oxidation levels start at on a virgin sample.
So in the case of redline, lets say the oxidation levels of a virgin sample is 22. Now this takes into account the wierd way the esters may effect this reading, so now when you read a used sample and it is say 48, the ftir would compare that with the virgin sample and subtract that from the 48 giving you an actual reading of 26%. This would be a correct level of oxidation. Also when looking at the oxidation, normally the viscosity will increase(how ever slightly) when oxidation levels increase.
The problem with why many oxidation levels reading so high with redline is that if the oil analysis company doesn't have a virgin sample data on file for that oil, they then go to a generic to compare against and most do not have those types of esters thus giving a "false" reading on the oxidation #'s.
This is true with most labs. Especially when you switch over from one api sj to api sl, now all the old sj data becomes worthless when comparing to the sl grade oils. But unless they have the newer api virgin sample to go against to compare a good starting point against the used, they then take a basic generic oil and its numbers and calculate the used oil against that.
Thanks for the reply. It all makes sense now but! There seems the possibility that a guy could send the excellent Schaeffers 10/30 Blend with a run of X miles to a Lab that did not have this baseline, POW! It gets compared to a inferior oil
If the guy did not know different,he might change brands because of the results? Yes? No ? If he was doing this himself for a small Fleet,it could cost him money = Whoooa!
[ October 13, 2002, 12:03 PM: Message edited by: dragboat ]