Fully Synthetic Oil Carbons Up Fast?

91BLOWNSC

Registered User
I am about 7,000 miles into a fresh rebuild and im using fully synthetic mobil 1. I do not burn any oil what so ever, and have used synthetic from the start (despite contrary opinions to this). My question to you guys is, those who have used synthetic and regular oil in the vehicles, do you notice that the synthetic seems to get a bit darker, faster? After about 1500 miles, it seems my oil is pretty darn dark. And my block was totally cleaned out, and all parts were cleaned. I change it ALWAYS before the 3k mark. Just wondering if this is normal from synthetic oil, and why it would be doing this. Thanks.
 
No, it is usually the other way around for me...

One of the reasons why I use Mobil 1 oil, is that it stays cleaner longer. At least in my experience. Often times it comes out cleaner from the bottle. Regular dino oil has a light yellow/honey color to it when new. But Mobil 1 is almost crystal clear. So that is probably why it stays cleaner a bit longer for me.

Also, you may want to look into your oil filter combo. For a while I was using cheap oil filters like Fram and Car quest. Now I basically use only Mobil 1 filters or Purolator Pure one filters. They have a synthetic media and are built to trap more contaminants. Therefore they help keep the oil looking a little cleaner for longer.

Lastly if your oil is getting dirty really fast, you may want to think about excessive hydrocarbons entering the crankcase. Did you use total seal rings? Or if you used gap style rings, did you stagger them on the pistons? Perhaps your fuel mixtures are on the rich side, or you have bad leaky injectors?

Just some other questions you may want to ask yourself, but like I said before, in my experience the Synthetic oil, (especially mobil 1) lasts much longer.... even though I change it every 3K miles.
 
What kind of oil filter are you using? I put the mobil 1 synthetic in my car the 3rd day I owned it. I love that stuff. Longest I ever went before changing it was about 4500 miles. Even then, it came out with some visibility to it, and only about a 1/2 qt low. I also had two leaks i found when tearing the engine down.

What weight are you running as well. I used 5w30 because the car was completely stock. With all the new stuff, I used their 15w50, comes with the red cap. Said something about being formulated for turbo/supercharged cars. I drive aggressively too. Once the car is fully driveable, I can better say how it works.

My only other thought was do you drive the car rough, high rpms, full throttlin it. And what temp stat you have also. I have a 180. Maybe it's not liking the temps of your engine.

Idunno, just a few thoughts off the top my head.
 
Oil getting black is a sign of excess hydrocarbons. This can be caused by a number of things.

1. Rings not seated properly due to improper finish. Did you break the motor in with conventional oil first? How about a compression test?

2. Low operating temperature. Is the motor running at or above 180 degrees?

3. Engine running rich. Any possible tuning issues? Did you install new O2 sensors?

Other than that, synthetic oil is very high detergent so it will keep the motor clean. Bad thing is all the crap ends up in the oil. Change your filter every 1500 miles at least until you figure out what the problem is. Change the oil at 3000 unless it is getting opaque quicker than that. Don't run with severely dirty oil.
 
I would be affraid of an oil that didnt turn black within a 1200 mile or so time period. The oil turning black only shows its doing 1 of its intended jobs well.
I'm a big proponent of synthetic oil and I've used the stuff for 20 years or so, but I'm very hesitant about breaking in an engine with it. I'm not saying you cant do that but be prepared for the break in to last much longer. I know guys that couldnt get there rings to break in and seal while trying to break in the engine on synthetic. We ended up switching back to dino oil and adding Risolene to the crankcase oil in order to get the rings to seal and after 3000 miles we switched back to synthetic.
 
If its any consolation I use a part synthetic in my car and i love it. Also i use a conventional MotorCraft Filter. No problems with the oil or looking rough.

And I always suggest breaking in an engine on conventional oil.
 
I've also used Mobil 1 since break-in (my '93 has 187,000m and my '94 has 108,000) and sometimes the oil in the bottle isn't that clear to begin with and, it really darkens up after about say 1,500m. I use 5W30 between say Dec & March and 10W30 the rest of the year. By the way the Purolator Pure One filter is not synthetic - just more densely packed. I believe Motorcraft filters are also Pure One's made by Purolator. I like the "Hard Driver" synthetic filters for about $7-8, but they are hard to find. Otherwise I use AC Delco's synthetic or the Pure One. Perhaps running a lower temp (I have a 200deg sensor/switch for the fans on my radiator) contributes to the carbonization but with those mileages I haven't had any engine problems.
Jim.
 
my oil also gets dark faster. I too use mobil 1. I dnt burn any oil, and i dont loose it. The car has 104k on it and runs strong. I think the oil is just doing it's job. Its a detergent oil, and is ment to clean the cylinder walls and the rest of the motor. I change mine about 2500 miles. My car runs about 195* all the time, with highs running about 200*. So my temp is within it's range. I wouldn't worry about it, my motor is fine. I would however use reg. oil for the break-in period, then go to a synthetic oil.
 
Hey guys I just picked up some CASTROL SYNTEC I'm sold on it.

5w-30 full synthetic. You Know how much. $4.78 per quart. is that a fair price. Is there really that much difference between the full syn and the blended. I remember it was like 2.50 back in the 80's .
 
I run Castrolin my car also... had it in the car for about 500 miles. I used to run part synthetic and switched to full synthetic with Castrol Syntec. I paid right at about 20bucks for a 5 qt container.
 
I wouldn't run the blended, they don't tell you what the percentage is. The way it's priced around $2.50 qt, you'd think it was 50%. But I bet it's a lot less. Just a marketing gimick.
Jim.
 
hmm...interesting.

I know some of you posted its doing its job, the only thing is, my engine was torn down and COMPLETELY cleaned out...so there really shouldn't be anything for it to clean. Yes the rings were set-up right. New 02 sensors were just installed so I hope I hope I am having the right air/fuel mixtures. But one thing that is odd someone mentioned was if it was running at the right temp. This i cannot be certain. It seams that sometimes my car has a hard time making it even to the N in normal. Sometimes it barely makes it past the first white line after the blue color bar. :S I have a 195 degree stat in there so I cannot see that it couldn't be running right. I have a slight miss at idle that I can't figure out. I do run my car slightly rougher than a normal person I would say. And If the rings wouldn't have seated...wouldn't I be losing oil? I even notice that the syntethic oil is darker than the conventional oil like Joisey Jim said. For an oil filter, I use the motorcraft FL-400S. I can spare the extra money for oil, but 10 dollars on a filter? Sometimes I just don't know.:confused:

Just an FYI, check at wal-mart next time for your oil guys. I got the 5 quart container of mobil 1 fully synthetic oil from there for 18.88. I thought that was pretty damn good!
 
Well rings leaking in a forced induction motor generaly shows up as blow by into the crankcase. Thanks to the pressurized intake you dont get much vac in the cylinders to pull oil up (to burn) but you do get blowby.
I wouldnt worry about the oil its normal to get dark in that time frame. You see when you dont change your oil regularly that black stuff which is carbon and byproducts of combustion coats and settles all in you engine. Thats not good.

I'm not saying your engine is dirty on the inside, I know your engine was cleaned in the teardown. But the darkness of your oil does not mean the inside of the engine is dirty, its just byproducts of combustion that your oil is keeping suspended(doing its job) to be drained out at the next oil change.
Just dont wait until 3-4000 miles before you change it or you will start building up that crud inside again.
 
5-quarts is the way to go...

I know it doesn't help your situation, but I also look for the 5 quart container at Wal-mart for $18.88. Compared to buying 5 separate quarts of 5w30 Mobil 1 for something like $24.00 it sure makes sense to get the 5quart jug.

BTW, I have 3 of them sitting in my closet now!!! :D

Running your car a little bit harder than the average joe might account for the additional build up in your engine. I normally drive the car like a grandma on the street. 2000rpm shifts and I rarely take the engine into boost. I don't see my oil significantly darken up until after about 1000 miles.

ANother reason why oil can darken up fast is not just dirt but also heat as it gets cooked by the engine. But then again, you've mentioned that your engine seems to barely heat up and you are running the stock stat.
 
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