How come the oil in my pretty much stock d16y8 gets dirty so quickly? I have a k&N filter which I cleaned and oiled up, no leaks in the intake system. I use oem filter and mazda 5w30 oil (cause I work there). I did my oil change again yesterday after 1500 miles and it was very black, like if I had driven it for 8000 miles. The colour of the internals is a normal light brown, I did a full engine flush 3 months ago.

I thought it was because of blow by so I vented the valve cover for fun. There is a lot of air blowing out the 2 holes at idle only. The engine doesnt burn too much oil. 1 pint per 1500 miles and I'm not kind with it. I only drive it hard when is engine is at operating temps. I have also changed the pcv valve.

Any ideas why the engine oil turns very black after 1500 miles for my last 3 oil changes?

 

sounds like contamination from blow by. The oil and compression rings are probably a little tired and contaminating the oil. There's really only 2 things that will turn oil black quickly, blow by or an extremely dirty engine from not changing the oil previously. I'd still go with blow-by.

 

hmmm, sucks cause this engine was always taken care of, and it wasn't driven hard in a stupid way. Any way I can reduce blow by without a rebuild? Could my black pcv box behind the block be clogged?

 

typically you'd have to run an oil additive to reduce blowby but that is only a band aid solution.

 

I understand, thanks for the information.