whats the deal with uoa and long drain intervals?

[subiedriver]

I'm perfectly comfortable running 7K OCI's in my Subie with Mobil 1 HM. All of my driving is highway, so my motor gets up to full operating temp for an extended period of time, 1 hour. This boils off all the chemical contaminants, water, soot, ect. I've had my valve covers off replacing the gasket and my motor pretty much looks like Overkill's 302. I was very happy.

One more thing, my oil still looks like honey, 3K into the OC.

 

[Quattro Pete]

Originally Posted By: electrolover
my question is: how much crud can oil dissolve and still lubricate properly? and how much crud can oil dissolve and not leave any behind?

But you're assuming that there is "crud" in the engine to begin with. Why?

Obviously, if you have a sludged up engine, then you need to deal with that first before jumping to extended oil change intervals. Most oils aren't strong enough to remove sludge. These oils' job is to prevent sludge from forming in the first place, but if you have an engine with a lot of sludge, you need to use other tools/means to get rid of the sludge first.

Long drains are only applicable if your engine is in tip top shape.

Quote:

and with out dissembling the engine do you really know if there was build up or not? and if the contaminates are low is it because the oil isn't cleaning like it should or just because the engine is running clean?

Good question, and I'm afraid this isn't something a $20 UOA can answer either. Sometimes you will see crud on your oil filter or on your dipstick, but at that point you probably already have massive amounts of sludge in there. So yeah, you'd need to pull the valve cover to see it for yourself.

 

[Virtuoso]

Cut your filter's open. You'll see what's going on, to an extent.

Even after only 2,200 miles, there's stuff in there. Very very little, for sure, but some. And you'd never know it looking under the valve cover of this van, it looks like Overk1ll's 302.

 

[electrolover]

i wonder if you can send filters in for analysis?
if a man did that, an uoa and took a look at it every now and then he would pretty well know what was going on in his engine.
i cut filters open all the time. in my vehicles i never see crud, in others...
but i cant tell how good its working or what exactly is in it