Black hole consuming oil, syn oil was a bad idea

I have an 87 XJ, 245,000 miles, that has had no real oil consumption since I bought it 2.5 years, 25,000 miles ago. The oil pan gasket, front and rear seals, valve cover gasket, distributor gasket, valve cover oil fill cap and gasket, and CCV lines, were all tight and recently (last 12,000 miles) replaced. The valve cover bolts are tight.

5 weeks ago I changed the oil using 1/2 quart of marvel mystery oil (I used it before on this engine with no problems) plus 1/2 quart of Risolene oil additive and the rest was 20W50 dyno oil.

After about 500 miles the two thin (MMO & Ris.) additives had burned off so I added 1 quart of oil like I usually do when using these additives. I tried a 20W50 Castrol synthetic, first time I ever tried a synthetic.

A short while later I had to add another quart. Used the synthetic again. The engine was and is still is running well.

Then I noticed the oil leak at the oil filter adapter. Fixed that 2 weeks ago. By the time I had fixed it I had already added another 2 quarts of synthetic (I allways used the 20W50 weight. Both the Dyno and recently the synthetic oils on this engine since about 18 months ago were all 20W50)

The oil consumption rate dropped from 1 quart/ 100 miles to 1 quart/200 miles after replacing the oil filter adapter o'rings.

There is no oil or smoke in the tail pipe exhaust. No oil on the drive way. The tail pipe is a dry black from running too rich. I was working out the sensor problems in the Renix system recently and it ran rich for a good while which explains the dry black carbon on the exhaust pipe.

I have noticed oil on the top of the valve cover coming from the oil fill hole, but the plug in it and its gasket are new and tight!?? I have wiped the valve cover top dry several times, almost daily.

All I can figure is the synthetic oils are exteemely good wetting (very low surface tension) and are wetting and leaking their way out by some kind of capillary action. I also see an oil drop under the oil drain plug on the oil pan but it is only 2 years old and maybe 6 oil changes old (the plug and gasket) and it is tight, and there are no oil spots forming on the driveway under the jeep!!!! I inspected the gasket and drain plug during the last oil change 5 weeks ago. They were fine.

The large front CCV line is new (2 weeks old) and it is oil free and dry. The rear, smaller CCV line is new, clean and clear. All the connections are tight. The valve cover bolts are tight and the cork gasket is only about 12 months, 8000 miles old. The small CCV line metering orifice (custom by me) is currently about 2.6 mm (spec is 2.2 mm) but I ran it at 3mm for over a year with out it eating oil before I fixed the valve cover air and oil leaks.

At least for the winter time conditions I have not seen any change in my oil pressure since I started using the synthetic oil for make up to replace the lost oil. I inspected the plugs recently and there is no blowby or oil consumption in the ring area (at least not before adding the dyno oil recently). The platimum plugs looked new with 15,000 miles on them.

So where is the black hole that is sucking up all this oil?????:bawl:

Well, first off Castrol Syntec is not a full synthetic...it's a dino-synthetic blend that goes through a completely different refining process than a full synthetic. It's marketed as a "synthetic" because of a case won in the courts by the makers of "combination oils" to market their products as synthetic against companies like Royal Purple, Mobil1, Redline, etc...

Second, how many miles per day do you drive? If you regularly drive short distances day to day (less than 50 miles), stop using the blend or any type of synthetic oil. What happens is the parafins in the synthetics will boil off, leaving condensation and scale build up. It's not good for your engine (particularly one with high mileage). With this boiling off action, this leads to some leaks as the condensation remixes with the synthetic/dyno oil in the form of water, which in turn greatly reduces the viscosity of the oil and leaking out of the biggest cracks it can find (typically the oil filter mating surface and the top of the valve cover where the fill is).

Bottom line, if you drive long distances regularly, every day; go with a synthetic or synthetic blend. If you only drive short distances (very little regular highway travel, or about 25-50 miles per day total), then go with regular dino oil and save yourself the headache of perhaps cheating your engine out of some miles.

dcXJ said:

Well, first off Castrol Syntec is not a full synthetic...it's a dino-synthetic blend

Click to expand...

There are 2 types of Castrol Syntec, full synthetic (black bottle) and the blend (gray bottle).

:repair:
I use synthetic oil in all of my Truck and my wifes car. My Jeep uses reg oil because I bought it used and it was not broke in on synthetic oil.

Do not change a high milage engine to synthetic oil it will burn off and leak like a screen door.

A older engine has a lot of ware so the synthetic oil will bypass the rings and be burned off. It will also seep past all the seals that have been seated in place with reg oil. Reg oil leaves deposits that help seal a older engine.

On a new engine synthetic oil will ware less and wash the engine parts clean. With a blend oil the syn in the blend will help keep the parts clean. The worst thing you can do for a older engine is clean it up. It need the deposits and some sludge to keep it running right.

I made the same mystake in a old ford truck with 280,000 on it the engine snapped a crank 700 miles after the change to synthetic. I was told by a engine re-builder that not to change over if it has over 30,000 miles.

Tugboat369 said:

:repair:
I use synthetic oil in all of my Truck and my wifes car. My Jeep uses reg oil because I bought it used and it was not broke in on synthetic oil.

Do not change a high milage engine to synthetic oil it will burn off and leak like a screen door.

A older engine has a lot of ware so the synthetic oil will bypass the rings and be burned off. It will also seep past all the seals that have been seated in place with reg oil. Reg oil leaves deposits that help seal a older engine.

On a new engine synthetic oil will ware less and wash the engine parts clean. With a blend oil the syn in the blend will help keep the parts clean. The worst thing you can do for a older engine is clean it up. It need the deposits and some sludge to keep it running right.

I made the same mystake in a old ford truck with 280,000 on it the engine snapped a crank 700 miles after the change to synthetic. I was told by a engine re-builder that not to change over if it has over 30,000 miles.

Click to expand...

boy, there's a lot of bad info in that post.
It's not the oil that's the problem, it's the old seals and such. I succeefully converted my 4.0 to synthetic at 240K. It doesn't leak, and my cold oil pressure and hot oil pressure are better for it.
I converted the wifes yota at 100K, same scenario.
All that nonsense about needing sludge is BS, yes, it's possible that the seals will weep, but then you need new seals, not old oil and sludge.

Anyway, I'd check your air filter, I knocked off a vac line one day and lost a quart of oil into the air filter in a week of driving. I noticed it dripping onto the tire one day and thought it was odd.

dcXJ said:

Well, first off Castrol Syntec is not a full synthetic...it's a dino-synthetic blend that goes through a completely different refining process than a full synthetic. It's marketed as a "synthetic" because of a case won in the courts by the makers of "combination oils" to market their products as synthetic against companies like Royal Purple, Mobil1, Redline, etc...

Second, how many miles per day do you drive? If you regularly drive short distances day to day (less than 50 miles), stop using the blend or any type of synthetic oil. What happens is the parafins in the synthetics will boil off, leaving condensation and scale build up. It's not good for your engine (particularly one with high mileage). With this boiling off action, this leads to some leaks as the condensation remixes with the synthetic/dyno oil in the form of water, which in turn greatly reduces the viscosity of the oil and leaking out of the biggest cracks it can find (typically the oil filter mating surface and the top of the valve cover where the fill is).

Bottom line, if you drive long distances regularly, every day; go with a synthetic or synthetic blend. If you only drive short distances (very little regular highway travel, or about 25-50 miles per day total), then go with regular dino oil and save yourself the headache of perhaps cheating your engine out of some miles.

Click to expand...

As stated by another, Castrol also makes a pure synthetic now. I used their pure synthetic in this case. I am not sure why the driving type (highway/non-highway) would cause parafin boil off? What do you mean by condenstation? Do you mean polymerization? Or sludge formation? Where would the water come from?

Tugboat369 said:

:repair:
I use synthetic oil in all of my Truck and my wifes car. My Jeep uses reg oil because I bought it used and it was not broke in on synthetic oil.

Do not change a high milage engine to synthetic oil it will burn off and leak like a screen door.

A older engine has a lot of ware so the synthetic oil will bypass the rings and be burned off. It will also seep past all the seals that have been seated in place with reg oil. Reg oil leaves deposits that help seal a older engine.

On a new engine synthetic oil will ware less and wash the engine parts clean. With a blend oil the syn in the blend will help keep the parts clean. The worst thing you can do for a older engine is clean it up. It need the deposits and some sludge to keep it running right.

I made the same mystake in a old ford truck with 280,000 on it the engine snapped a crank 700 miles after the change to synthetic. I was told by a engine re-builder that not to change over if it has over 30,000 miles.

Click to expand...

Tugboat369,

Even though this is a high mileage engine, I bought it used at 225,000 miles, I suspected when I bought it that the engine had been previously worked on (partly rebuilt) as it used no oil when I bought it! So I figured (maybe incorectly) that it had new piston rings, and possibly other newer wear parts replaced already. Since I bought it I replaced most of the known seal parts and gaskets and the main crank bearings and oil pump, and I checked the rod bearings which were still in spec (still almost new) so I felt safe from an oil seal and rings standpoint trying some synthetic as an additive. I started out with one of 6 quarts being pure synthetic.

Lastly, with the exception of the small CCV tubing line which was plugged with sludge and the upper parts of the Valve cover itself, the engine, oil, and oil pan were fairly clean, sludge free further convincing me that this engine had fairly new parts in it before I bought it (except for the main crank bearings which I replaced with the oil pump when I got concerned about low idle oil pressure one day)

Ecomike said:

As stated by another, Castrol also makes a pure synthetic now.

Click to expand...

What dcXJ said is correct. He wasn't referring to Castrol's syn-blend (of course that's not full synthetic) ... he was referring to their "full-synthetic" Syntec in the black bottle. It turns out that Castrol's full synthetic oil isn't really fully synthetic. Mobil 1 sued Castrol on their claims and lost in court.

Here is an article describing the issue: http://www.pecuniary.com/newsletters/syntheticsdefined.html

Here is another article describing how Castrol Syntec uses API Group III oils as it's base stock, and how Mobile one and the others who make a true synthetic oil use API Group IV oils as their base stock. Group IV bases are better:
http://www.sportrider.com/tech/146_0308_oil/

Group III oils start out as regular dino oil and are processed to remove impurities, resulting in a more heat-stable compound than regular dino oil. But ... they aren't as good as Group IV bases. Group III oils are also MUCH cheaper to manufacture. They also discuss the lawsuit that resulted in Group III base oils now being called "Full Synthetic."

Here's another article that shows testing done by a physics professor/motorcycle enthusiast. After 1500 miles in a motorcycle run on a test stand, Mobile 1 lost 17% of it's original viscosity. Castrol Syntec lost 25.5% in the same bike run through the same test :
http://www.xs11.com/stories/mcnoil94.htm (scroll down to the bottom table).

I used to be a big Castrol fan ... they always made very good dino oil, but after I learned this, I stopped using Castrol Syntec and switched to Mobil I. I believe Mobil 1 is a better oil, because it is built with a superior base stock.

87manche said:

boy, there's a lot of bad info in that post.
It's not the oil that's the problem, it's the old seals and such. I succeefully converted my 4.0 to synthetic at 240K. It doesn't leak, and my cold oil pressure and hot oil pressure are better for it.
I converted the wifes yota at 100K, same scenario.
All that nonsense about needing sludge is BS, yes, it's possible that the seals will weep, but then you need new seals, not old oil and sludge.

Anyway, I'd check your air filter, I knocked off a vac line one day and lost a quart of oil into the air filter in a week of driving. I noticed it dripping onto the tire one day and thought it was odd.

Click to expand...

87manche,

Interesting! A success story for synthetic on an old engine!

Which synthetic are you using?

In my case I have already adressed all old seal issues on mine. The air filter is fine. I recently fixed the entire air filter, CCV system, before the oil experiments. I did find some oil in the small CCV line this morning, the leading to the intake manifold. I replaced the 2.6 mm orifice with a 2.0 mm orifice this morning.

I am beginning to suspect the reed valves in the valve cover need replacing on mine, (see post number 10 & 11 in http://www.naxja.org/forum/showthread.php?t=908048 ) but since the flow out of the valve cover is normally through that small CCV line anyway, I am not sure that replacing the reed valve on that small CCV fitting will fix the problem. I wish I new more about the two CCV reed valve assemblies in the Valve cover such as what they are supposed to do and when, and how they should look and operate in the jeep 4.0.

I do believe that one should be very careful and cautious when changing oil types in an older engine, and they should be prepared to fix "old seal", seal leaks right away. They should also be concerned about releasing large amounts of sludge in an old engine if it has sludge in it, and should be prepared to change oil filters and oil pump intake screens after a very short time as the filters and screens can plug up quickly if bunch of parafin waxes and sludge come loose all at once!

I've found that running a synthetic blend is the first step.
I ran a synthetic blend in the yota.
She's got the 5sfe engine, a motor that is notorious for sludge, in fact, toyota just sent us a warranty card as a result of a class action lawsuit. The motors would sludge up the oil passages and starve the cam for oil, then the motor would self destruct.
Anyway, I ran a few oil changes of high mileage synthetic blend, then changed it over to full synth. I figured that the high mileage blend seal conditioners couldn't hurt. I changed those at short intervals, 1500 miles. Then made the switch to mobil one full synth 10w30, changed the first one at 3K, and now it's on extended maintenance of an oil change every 5K.

The heep was a different story, I ran some high mileage stuff in that, then I switched it. I got an oil leak out of the oil filter adapter, but it's a 20 year old motor so I expected that. I replaced the o-rings, it's fine. I also replaced the valve cover gasket, but that leaked with regular oil as well.
I did clean up the valvetrain on the 4.0 before I switched over, and again, went with an aggressive oil change interval for the first two changes.
Now it's on a 5K mile program too, unless I abuse it, then it get's changed just because.