When you take an oil sample there are things you can do to make the sample representative of your oil. If a sample does not represent the true condition of the lubricant and component at the time of sampling, the reliability of both the test results and the interpetation is effected.
1)Make sure the oil is hot (at operating temperature) when you take the sample.
2)Get the sample from the same place at each sampling.
3)If you use the drain plug to get the sample from, make sure the area around the plug is very clean before the plug is removed. In the case of the Cummins engine, the plug can just be loosened, and oil will start to drain.
4) If drain plug is your choice, do as Bigsaint said, allow some oil to flow before catching the oil for the sample.
I think the best place to sample oil is from the "Dip-Stick", as there is much less of a chance for contaminants to be picked up there. This can be done using a plastic tube and a syringe.
Amsoil Inc. does sell a sampling kit for $14. 00 including postage. The stock # is:G-1451. They also have a sampling pump including 10 ft. of tubing for $24. 50 Stock # is:G-1206. This allows a sample to be taken from the dip-stick.
The actual oil analysis is performed by "Oil Analyzers Inc. "
Wayne
amsoilman