Synth oil... leaks or not (ONLY real experience vote)

No leaks.....no "Ferrari drops" either.

All cars Mobil 1 diff grades.

 

I have experience -- but it's not in a Ferrari. Does that count?

I use synthetic oil in any car that I hope to keep more than six months. No leaks. That included using the 15W-50 or 5W-50 stuff in my 1983 Jaguar V12, which I believe is far more notorious for leaking oil than a Ferrari. However, I probably need to qualify that answer.

My Jaguar V12 had been apart, and I had scrupulously sealed it. There are a few places it's going to leak if assembled according the manufacturer's specs. One is along the threads of the bolts holding the oil pan to the block. That problem was discovered by Jaguar; they issued a TSB describing how to take the bolts out, clean the threads, apply a thread sealant, and put them back in. Nuthin' to it, but if you don't do it the engine is going to leak, synth oil or not.

There's also something called a "half moon seal", a rubber semicircular plug at the back end of each cam cover. It is an inherently bad design, and will always leak sooner or later. There are at least three different ways to fix it; the one I chose was to make plugs from solid aluminum and seal them with Loctite 573 or 574. It won't leak, ever. But with the OEM rubber plug, it's going to leak, synth oil or not.

The one that's perhaps most telling: The valve stem seals in my engine had openings that were perhaps 10% larger diameter than the valve stems they were supposed to be sealing against. You can't get there from wear; once the seal no longer contacts the stem, wear ceases. The only way these seals could have gotten to this point is by swelling.

The OEM valve stem seals were made of neoprene, the same thing that O-rings are made of -- and often other seals and gaskets used in engines. It's my belief that the motor oil companies often add additives that are intended to make neoprene swell, because it'll make an O-ring seal BETTER. It wouldn't surprise me to learn that the synthetics make neoprene swell more than dino oil, possibly in response to the persistent rumors that synth oil causes leaks. But in the case of these valve stem seals, the scheme backfired. Of course, the result isn't so much an oil leak as oil burning, but it's all bad.

My solution was to install Teflon valve stem seals. Once you have a Teflon valve stem seal in your hand, you'll never install an OEM rubber valve stem seal again. They clearly will seal, period. The OEM seals are used on the intake valves only -- the exhaust valves get no seals -- but with the Teflon seals you can put seals on both intake and exhaust and eliminate any loss of oil via the valve stems.

My advice to others is simple: if your engine leaks oil, don't blame the oil; fix the leaks. And sometimes just putting the parts back together the way the repair manual says to is not good enough; you need to think about how the oil on the inside is kept separate from the great outdoors and make sure that separation is secure.

 

My Daytona has run Mobil 1 synthetic since the engine was rebuilt 18 years ago. In that time and 20K miles or so, no leaks. The PO drove the car a couple of times a month, but for just enough miles to warm it up fully. He did however change the oil every 6 months even if only 300 miles had been covered.

The only first hand experiences or stories I have heard about synthetic causing leaks is when a car was run on dino oil for many years and then switched to synthetic.



Terry

 

Like I said earlier, you guys should seriously read some back issues of the STAR magazine, the official Mercedes Benz club magazine. I would stack MB engine and gasket design and technology against any car in the world, at least the stuff built up to 1990. And up to that point in time, MB had cars that were well known for accumulating hundreds of thousands of miles without major engine work on plain old dino oil. My god you guys, you know this is true, I don't get the argument here at all, this is all well known information. So now when you admit the cars leak oil on synthetic, instead of changing oil, you want us to R&R our engines and overhaul them?

Which one of you guys wants to yank the 7.3 diesel out of my truck for me and put all new gaskets and seals in it so I can run synthetic? It leaked like a sieve on synthetic, the oil it ran by the first owner for almost 180,000 miles, but now doesnt leak a drop. The reality is that I should get well beyond 400,000 miles on this engine without doing anything to it at all, why would I want to pay more for oil? Can someone show one statistic of synthetic getting higher miles out of an engine? Maybe Mobil should fix thier oil.

 

Actually, I have no argument with the contention that you can get an engine to run a half million miles or more on dino oil. If you change the dino oil often enough -- every 3000 miles is what's commonly recommended everywhere except in the owner's manuals -- any good quality dino oil should provide good service and good wear protection.

But I use synthetic oil for other reasons. First off, I don't like changing my oil every 3000 miles. I use synthetic oil and change it per the manufacturer's recommended intervals, which seems to be about 7500 miles on most modern cars. I do change the oil filter twice as often as I change the oil, though.

But the main reason I use synthetic oil is for the cleanliness of the internal parts. When an engine has been run on dino oil, the insides are usually all caked up with varnish. It's my suspicion that the varnish seals gasket leaks, which is why synthetic oil -- which dissolves the varnish -- causes leaks in many cars. This is especially true with older cars that still have sorry paper gaskets, since paper is inherently porous and oil will tend to soak through if it doesn't turn to varnish on the way.

When an engine has been run on synthetic oil, the insides are usually clean as a whistle. During an overhaul, you can pretty much just bolt parts back together -- no need and no point to having to scrub or soak or sandblast or whatever.

Does this make any difference? Perhaps not, especially in a beater where a rebuild simply isn't going to happen. But in the Jaguar V12, for example, the varnish buildup has been known to cause sticky valve tappets, which in turn causes nasty backfires through the intake system at idle. It also gums up things like the pressure relief valve. Since Jaguar (Ford) went to gortex gaskets around 1990 and the new gaskets fit the older engines, anytime the engine is apart for work the sorry paper gaskets should be replaced with the new gaskets which don't rely on varnish to prevent leaking. Then you can run synthetic oil without worrying about leaks, and the engine will stay clean inside and you don't have to worry about varnish buildup.

 

Previous post was about my 308...my 348 leaks nothing and has Mobil 1 synthetic in it.

 

I use mobil1 0W40 with no leaks. Do have a few drips with the purple in the tranny though.

 

I switched from Agip sint 2000 10-40 to castrol 20-50 and a leak i had vanished...

 

It makes sense that synthetic oil "could" leak where conventional oil wouldn't simply because synthetic is more fluid. If you put a conventional oil and synthetic in the freezer till about zero degrees, pour both out and you'll see a dramatic difference, but wouldn't you rather have a more fluid oil during start-up ?
(The difference at room temperature is less obvious but still there, that's why I like the freezer test)

 

My experience with Synth oil has not been good in three different engines. All three of thes engine were rebuilt with new seals and gaskets. The engine vintage ranged from 1959 - 1977. The problem area was the main seals on both the front and rear. The engines were run on dino oil for the first 3000-5000 miles then switched over to Red line 20W - 50W. In all three cases the engines used 2-4 quarts of oil per 1000 miles. When switched back to dino oil the leaks dried up in 100-200 miles. Why was I so persistant in trying to use Synth oil? I have read several independant studies by SAE that showed the significant advantage of Synth oil with regard to bearing loads and wear. I do run Synth oil in all of my cars made after 1980 with no problems. I know Redline makes excellent products and use them in gear boxes, differentials, and engines whereever I can. This includes a 1986 TR, and a 2000 dodge truck. In my 2005 Maserati I use the oil recommended by the factory to maintain the warrenty which is Agip Synth 5-50W.

I also just learned that the Dino oil made since 2001 has significantly reduced the zinc and Phosphorous. This was done to reduce emissions. These two ingredients are key to cam and cam follower wear. So if you can not run Synth oil because you have an old engine then you should run a dino racing oil or a diesel truck oil. Both of these maitain the higher loading of zinc and phosphorous. New engine design has reduced the size of the bearings in in most areas to reduce drag which give more power and better gas milage. I believe this is the reason most new high performance engines require Synth oil.

I certainly believe there are many Mercedes that have run 300000 miles or more without engine rebuild and with dino oil. But these engines do not run at high rpm for extended periods of time and most never run at high rpm at any time.

So for you non believers I urge you to do a little more research before you decide what kind of oil you use in an engine that can cost $25000 to rebuild.

 

Engine or Transaxle fluid?

There is a difference in applicability