I don't know. The instructions on the test kits( that I use) state to do a clean catch at the drain

 

it would be nice if the outlet was threaded so, you could install a small plug to stop up the hole. Just incase the lever were to open . Also, my drain plug is flush with the botton of the oil pan.I sure would hate to knock this valve off going off road..I was also looking at the Fram sure drain system. I use to have it installed on several of my vehicles. I don't think it's made anymore

 

You may be able to do it at the filter, but I'd let the testing facility know where you got the sample. Remember that the filter is full of all the crud, so oil from there could be the dirtiest.

If I were running extended and needed samples, I'd put a second drain plug in with an extension tube that reached into the pan to the midpoint of the oil level and draw my sample from there. Otherwise just pull a sample from the drain pan with a valved drain and pour the extra oil back into the engine.

 

You're right! Not sure why I said oil pan isn't the best place. I corrected my original post.

 

I have an 06 and have taken a couple oil samples through the dipstick with no problems. I can't get the tube down the auto tranny dipstick tube bit the engine oil dipstick is fine.

 

Which year of truck are you doing this on? My truck is a 2005. Also, what size tubing are you using?

 

I used a 1/4" tubing.

 

HL, that is the same size I am using, but when I insert my tubing in dipstick tube it goes so far then hits whatever inside. What are you doing different? I bet the others would like to know also. Thanks buddy!

Darrell