Which Oil Please?
Discussion
I've heard lots of people blame oil leaks on synthetic oil.
What actually happens is over the miles there's a gradual build up of contamination inside the engine, which is usually due to over extended service intervals and the crappy, short lived additive package in the basic oil used by most garages as a cost cutting excercise.
One of these additives, Castrol call it a plasticlear, is designed to keep oil seals supple. Like most of the addatives in ordinary mineral oil plasticlear looses its effctiveness between oil changes,
The build up of glaze and contamination in the engine over time coats the rear of the seal which eventually prevents the plasticlear from protecting the seal. Repeated heat cycling and build up of combustion by-products in the oil then attack the seal causing it to become brittle. Once the seal has hardened it is no longer able to flex on the crank and instead begins to wear. Once this happens the existing build up of contaminants and glaze on the seal are the only thing preventing the seal from leaking. They can, in some circumstances do this extremely well for a long period.
Enter the new synthetic oil, with a much more effective detergent package than ordinary mineral oil, which strips the glaze and crap off the seal exposing the wear and suddenly there's the oil leak, hence the blame on synthetic oil.
The only real answer is to remove the engine and change the seal, which is a bit of a bugger on the V12. It might, as a tempoary fix, be worth checking all the breather hoses are clear, a blockage or restriction will pressurise the sump and make the leak worse, and trying the highest viscosity oil you can fill with.
One or two drips overnight is not bad - I've seen V12s leaking like a pissing horse.
There's just a chance if you stick with synthetic oil, the seal may regain some of it's flexibility and slow the rate of leak down. Avoiding full throttle and high revs will help too.
JS
What actually happens is over the miles there's a gradual build up of contamination inside the engine, which is usually due to over extended service intervals and the crappy, short lived additive package in the basic oil used by most garages as a cost cutting excercise.
One of these additives, Castrol call it a plasticlear, is designed to keep oil seals supple. Like most of the addatives in ordinary mineral oil plasticlear looses its effctiveness between oil changes,
The build up of glaze and contamination in the engine over time coats the rear of the seal which eventually prevents the plasticlear from protecting the seal. Repeated heat cycling and build up of combustion by-products in the oil then attack the seal causing it to become brittle. Once the seal has hardened it is no longer able to flex on the crank and instead begins to wear. Once this happens the existing build up of contaminants and glaze on the seal are the only thing preventing the seal from leaking. They can, in some circumstances do this extremely well for a long period.
Enter the new synthetic oil, with a much more effective detergent package than ordinary mineral oil, which strips the glaze and crap off the seal exposing the wear and suddenly there's the oil leak, hence the blame on synthetic oil.
The only real answer is to remove the engine and change the seal, which is a bit of a bugger on the V12. It might, as a tempoary fix, be worth checking all the breather hoses are clear, a blockage or restriction will pressurise the sump and make the leak worse, and trying the highest viscosity oil you can fill with.
One or two drips overnight is not bad - I've seen V12s leaking like a pissing horse.
There's just a chance if you stick with synthetic oil, the seal may regain some of it's flexibility and slow the rate of leak down. Avoiding full throttle and high revs will help too.
JS
.richard said:
Have same engine in 1996 XJ 6. Told to run it on fully synthetic. After changing oil to FS got an oil leak(one 2 two drops a night). Went back to semi and still had a leak. May be wrong but was this engine not designed before fully synthetic was even thought about.
I put in 20w50 Exxon Superflo. So far so good.
After going back to SS went back again to FS(Change myself) once a year. Don't use additives(Why should you?) and don't use any oil between changes. Sure this engine was not designed for FS considering age and manufacturing process at time. Tremendous engine. 90000 miles and 11 years. No problem.
.richard said:
After going back to SS went back again to FS(Change myself) once a year. Don't use additives(Why should you?) and don't use any oil between changes. Sure this engine was not designed for FS considering age and manufacturing process at time. Tremendous engine. 90000 miles and 11 years. No problem.
My seems to be purring at 87,000. I am going to have the plugs and fuel filter changed. No plug wires, that's good, but how does one go about testing each of the six mini-ignition coils for functionality? There is a slight miss on occassion with no discernable pattern. Hopefully the above actions will correct that; if not, I suppose a look at the injection is in order. I have done a couple of pour-in injector cleaner treatments. A little better, but still there.
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