Burnt oil, but no smoke or milky oil

[Shadowgundam'93]

Hey Everyone,
I'm new to the forum, I tried to search for this but only came up with one thread that wound up not really going anywhere but did notice to put as much information in each post as possible. I live in North Carolina (Mild Climate) and I have a 93 240sx hatch 5-speed swap (Engine rear main seal was replaced during swap) with a KA24DE with 167k miles that as not been modded in anyway that I am aware of. I am running Mobil 10-30 motor oil and Mobil one extended performance oil filter, OEM spark plug wires and NGK copper plugs. At oil changes there is no sludge in the oil pan all of the oil seems to be of regular consistency. After roughly three hundred miles the oil is burned and black as it can be. The motor does not smoke on start up, after long idle (Let it idle for 1.5 hrs just to see if it would smoke, after reading some other threads of long idles with smoke) or long drives. Spark plugs were clean and free of oil or gas last time I checked them. There is a very minute oil leak (less than 1/2 quart in 3000 miles) in the oil pan gasket at the back of the oil pan, which I will be getting replaced early next month. I don't believe the oil leak would cause this but at this point I feel like I've look all over the car and can't figure this out. I have read that dark/black oil is normal for the KA but it does smell burnt to me. Does anyone have any suggestions of where to look,another way to diagnose or personal experience with the same situation? Thank you in advance for any input.

[veery]

Could it be color bleed from the new rear seal? Any sign of high temperature?

[Shadowgundam'93]

Could it be color bleed from the new rear seal? Any sign of high temperature?

The rear main seal was just put in four weeks ago and the burning oil has been an on going thing before that. I replaced the rear main seal when the automatic transmission went bad and I decided to go to a 5 speed instead trying to figure out what went bad in the automatic. Everyone was guessing TCU or valvebody but couldn't be sure and I did not have the luxury of guessing wrong and being out all that $$$. The car has over heated once about 3-4 years ago when the mechanic who replaced the timing chain forgot to tighten the upper radiator hose clamp. I was on my way home from picking it up when the temp jumped straight up, I immediately pulled over and found the problem. I left the car to cool and had my wife take me to get antifreeze, after letting the car cool,tightening the clamp, and adding the coolant I had no troubles. The only other time the car has even got above the 1/2 point was when it was idling for the 1.5 hrs about 4 months ago. Even then it only got up to 3/4 and I was questioning the fan clutch because it was not engaged when I noticed the temp was up. I haven't notice the temp being abnormal other than these two events in the 4 years I've owned the car. Thanks for responding, if you have anymore questions or suggestions please let me know.