When an engine experiences blow by, does this cause the engine oil to get black from fuel or oil? I am trying to figure our why low tension oil rings can allow oil/fuel to get by and cause the oil to blacken, as fuel is lighter than oil and would seem to get by the rings easier. My plugs are fine and not black at all, but my oil gets black within a couple hundred miles of normal driving. And if this is the case will a catch can system remove this problem of getting the oil contaminated.

 

That's from some of the combustion process (carbon) getting past the rings. An engine that seals up like a drum with very little or no blowby will take thousands of miles to color the oil black. My "driver" is an Acura TL and the oil will still be reasonably clean (almost clear) at 5000 miles (the interval I have been using to change it). I cant believe how clean it is knowing how many miles are on it since the last oil change. Very little of the combustion process is getting past the rings obviously.

Tony

 

I agree completlely. I've come across 2 turbo engines dynoed to full power far to early. The oil goes black from the particulates and they get bore washed. Out on the track they are liable to seize if bore washing as the oil gets washed off the bores. They need running in first before they get loaded up on a dyno.

Steve, how many miles have you done and are you running a thin oil and rich fuel mix? The compression rings should have sealed your bores.

Boosted.

 

I can answer your last question...the catch can will do nothing to solve this problem. Mine has always done it, catch can or not.

 

I have around 6000 miles. I use Mobil 1 10w30. The engine runs 12.8 A/F ratio at WOT and otherwise is tuned to be 14.7.It runs clean, but when I floor it it does the typical GM black cloud of fuel for a quick second, then it is fine.
The compression is 190-195 in all bores and it was broken in very well, useing the run hard method recommended here, http://www.mototuneusa.com/break_in_secrets.htm
I know people with LSx engines had oil control problems early on and catch cans helped. I am going to use this can set up, which is actually designed for oil.
http://www.conceptualpolymer.com/PCV...oval%20101.pdf
Obviously I need to take her down and re ring it with standard rings, but until then I am trying to control the blow by economically.

 

maybe the break it in hard method is to blame here, it'd be interesting if you re ringed it and babied it during break in and sent a sample of each oil out for testing, I know there are lots of discussions about which method is best right now.
AJ

 

I thought about that, but being it that there is many people that have different thoughts on breaking in an engine. I have never been easy on a break in on engines, and have done 5 engines in my lifetime. Not much, but they all worked fine. This is the only one that used low tension rings, and PCV system, as the rest were older type engines with valve cover breathers.

 

I believe Honda uses a moly additive in the factory fill to aid break in, and their motors have a pretty good reputation for longevity. There is a company called Mr. Moly that makes a special break in additive. It is a soluable moly, rather than the more familiar "plating" type. I used it on my 2004 GTO and had no oil contamination or consumption issues, and it would take quite a while for the oil to darken.

 

Interesting discussion.

My 4Runner goes 5000 miles between oil changes and the oil never discolors. It has 105,000 miles on it.

But my Chevy diesel pickup will turn fresh oil completely black just by driving it around the block.
I guess carbon from the combustion. It has always done this and it has 103,000 miles on it.

The LS1 is ready for an oil change (Mobil 1, 5w-30) and it is only slightly darker than fresh oil. It has about 6000 on the oil and 31,000 on the engine.

 

GM EOS and even STP can help with break in. But mine has Moly rings, which break in real quick. When I did pull my engine down last year, the cross hatch pattern was still on the bores, the pistons looked good. My compression is real good also, 190+-a few pounds tells me the compression rings are broke in.
The low tension oil rings are the big problem I think with the blow by, and blackening oil.

 

"The low tension oil rings are the big problem I think with the blow by, and blackening oil."

Yep, you have found the problem.

 

"It runs clean, but when I floor it it does the typical GM black cloud of fuel for a quick second, then it is fine. "

excessive "PE" fuel being added?

 

You have never been behind a chevy when someone floors it and a puff of black smoke comes out, then goes away?

 

fact, yes I have. For maybe the last 50 yrs I've involved with cars...
Maybe a useful contribution, instead of wiseass comments??

 

Steve,

I'd say it's run in properly given your cylinder pressures. If the oil rings weren't scraping the bores properly you'd have oil smoke from the exhaust pipe and the compression rings would never bed in. My guess is that on hard accelleration your running rich momentarily. As for the black oil in the pan, do you have large ring gaps? Do you ever rev the car when cold or blip the throttle before shutting the motor down?

Boosted

 

Nice. I wasnt being a wiseass. Real mature, DH.

 

Here is a copy of my build sheet.
I do blip it sometimes.

 

get bent *******...

 

Imo there's nothing wrong with the build sheet Steve. Ring gaps are ok, I wouldn't worry about low tension rings either as I suspect the stock rings are low tension. The build sheet may be referring to low tension compression rings. The oil rings could be regular tension. A low tension compression ring frees up power but I can' really see any logic behind a low tension oil ring? Not for the street.

Next time you change the oil stop the blipping etc and see if that makes a difference Or, maybe try a different viscocity.

Boosted.