When is the best time to take a UOA sample?

[martyi]

I am about ready to dump the factory fill in my Honda VTEC-6 engine. My OLM shows 30% oil life expectancy (5300 miles) and I'll change oil with Havoline 5w20 at 6000 miles.

I will install a Fumoto valve when I change oil so taking samples should be easy. Should I wait until I change the oil when the monitor shows about 15% (when the oil service due light comes on) to see if the TBN and other numbers reflect the OLM's figures? Or should I take the sample about mid way (say after about 3000 miles), top-off and determine if indeed I can go another 3000 or more miles? I guess the question comes down to is it better to wait to take a sample when you change oil or at some point beforehand? PS-I use LC20.

 

[daemonite]

i'd take it at 15% to see the TBN in reality rather then predict the TBN @ 15%

 

[mshu7]

Regarding the Fumoto valve...

You might want to check out the FRAM Sure Drain. It's basically the same thing for about half the price I believe ($13). I put one on my dad's '04 Colorado and it's great. No leaks at all.

Although, I just tried finding it on FRAM's website and it's not on there anymore like it used to be. They sell them at Auto Zone & Advance Auto.

It might be worth at least checking out.