What is the correct procedure to draw an oil sample?

[rweis]

I have installed a bypass filter with the return line back to the oil filler cap.



I will need to draw an oil sample to send in for oil analysis.



What is the correct procedure to do that?



The engine will be running.



I read on an indusrty oil site that you should draw 2 samples into the container that will be sent in and dispose of the contents of both of those before you draw a third sample to send in. I think the intent was to flush out the sample container to insure no foreign material was in the container to be sent in.



Should I use the return line from the bypass filter (engine running) of should I use the oil drain in the bottom of the pan instead (engine not running, or the engine could be running) so as to not draw from the output from the bypass filter and get a more representative sample of the volume of engine oil? Or would it make any significant difference?



Ideas?



Bob Weis

 

[RollOver_Pete]

Um... . I guess you could do the double flush method like you talked about, but I believe that the container that you place your sample (oil) in slould be sterilized and sealed... I've done hundreds of them. Mayonnaise jars won't work . There are three ways I draw samples. Through the dip stick or the oil fill tube, both use a length of plastic tubing to a vacuum plunger which draws the oil out directly into a sample bottle. Any Caterpillar parts store sells them. The third way is through the drain plug. The plug is removed and after the oil drains a bit, I grab a sample by simply holding the bottle under the stream. You want the oil that would be in the center of the pan. Not the top or bottom. As far as breaking apart an oil return line and running the engine ... seems kind of risky, don't you think . The chance of you breaking a fitting or developing a leak with a running engine are too great :{ .

 

[rweis]

The sample containers I got from the lab are closed and sterile. Mayonnaise jars are not a good choice



The oil return line is a line from the bypass filter back to the oil filler cap and it dumps the output from the bypass filter into the top of the engine in a 1/8" very low pressure stream. There I would just loosen the oil filler cap and get the sample there, but it is after it has been through the bypass filter and not really representative.



I'll find a local Caterpillar store and see what they have. I want to get the sample from the middle of the sump if I can.



Thanks,



Bob Weis

 

[RustyJC]

Ideally, one would want to draw a sample from a dynamic, flowing point in the lube oil system between the lube oil pump and the first filter/strainer in the system. That's what we do (and the analysis/lube oil companies recommend) on the large industrial engines, gas turbines and compressors our company has manufactured. If you can't get in ahead of the primary filter, I might try to get a sample valve installed in the supply line ahead of the bypass filter.



The idea is to get a sample of what's circulating through the lube oil system, not what's lying in the bottom of the oil pan or any other static area of the engine.



The purging routine is to flush out any debris that might have settled in the sample valve or the static portion of the supply line to the sample valve.



Rusty

 

[paccool]

I installed a needle valve in a tee at the supply connection into the bypass filter. This is oil that has not gone thru the bypass and is easy to get a sample. Has worked good for me. I flush the valve for a few seconds after opening to flush out any debris.

 

[Pawpaw]

OK, I've got to ask... What's wrong with taking the sample after it comes out of the bypass filter?



I thought the purpose in sampling was to test the condition of the oil and the levels of various elements that are held in suspension. It seems that taking the sample after the bypass would only mean the larger particles (debris) has been removed from the sample by the filter. Would this really skew the analysis?



Please educate me.



Bob

 

[RustyJC]

There are two purposes for sampling oil:



1. To determine the condition of the oil



2. To determine the condition of the oil-wetted surfaces of the lubricated equipment



Sampling after all filtration has taken place will not affect the analysis results at all as they relate to purpose #1. For purpose #2, however, it is valuable to have all wear debris that's circulating with the lubricant in the sample being analyzed.



Rusty

 

[rweis]

Rusty,



I was hoping you would comment.



"If you can't get in ahead of the primary filter, I might try to get a sample valve installed in the supply line ahead of the bypass filter.



The idea is to get a sample of what's circulating through the lube oil system, not what's lying in the bottom of the oil pan or any other static area of the engine. "



I can makeup a tap to draw the sample on its way TO the bypass filter.



Thanks,



Bob Weis

 

[RustyJC]

Bob,



Unless there's a plugged oil gallery port between the pump and filter housing where you could put a sample valve, your solution sounds like probably the best you can do. There's really no need to waste a 1/2 quart of oil flushing out the sample valve - letting it run for 5 or 10 seconds is probably plenty if the valve is right there at the top of the existing filter mount housing (i. e. , you don't have 3 ft of static line before the sample valve. )



Rusty

 

[CumminsPower98]

I personally installed a test vavle on top of the bypass filter outlet as per Amsoil's diagram, which I flush before sampling. I can see the reasoning behind sampling before the filter but it seems to me that if the filter is doing it's job that the oil throughout the system should be pretty uniform but I'm no expert...



Mark

 

[Nate]

This oil sampling is all nice and good, but really what are you going to do when you find out what's in your oil?



Personally I could care less as long as the engine is still running fine, big deal what's in the oil.

 

[CumminsPower98]

I will tell you what good it does. My last test told me it was time to change the oil. I had 61k on the oil at the time of sample...

 

[Nate]

61k? :--) I'll change mine every 6k like the book says I think.

 

[CumminsPower98]

When running a good oil and bypass filter system and taking samples you can extend your drain period by a long shot. There are people with over 100k on their oil. Adding oil and changing filters as you go along helps the oil stay where it should be. I would be going nuts if I changed oil every 6k as those miles come on in a few weeks so this works well for life on the road as mine is right now. But for those using cheaper oils and not racking up the miles in a hurry as I am more frequent changes are fine.