Re: Synthetic Oil

["Kirbert" <palmk@mailer.gadcomm.net>]

Cosmo <simond@london.informix.com>:
> Interesting theory.  I tried the new Mobil 1 0w-40 oil recently in my SIII
> XJ6 and also got leaky rocker gaskets.  Haven't needed to remove them so I
> don't know if they are clean inside.  A number of other minor drips appeared
> on the floor but I had to cut short my experimentation due to the terrible
> oil consumption.  I was burning oil like James Bond's Aston Martin.  Quite
> embarassing.  Seemed to lessen greatly after 800 miles but by now that oh so
> wonderful oil had turned to the kind of sludge you see at 5,000 miles.

Another theory I'm working on -- the synthetic oil also may break loose stuck 
piston rings after a while.  Stuck piston rings are apparently a real 
problem, they seem to be often at fault when an engine is overhauled for oil 
burning.  Perhaps removing all the varnish allowed your rings to leak badly, 
and after a while the rings broke loose from the piston and started sealing 
again.

I am currently adding a bit of two-cycle oil to my gasoline.  I am hoping 
this may also help things like sticking rings.

Or, the oil may have washed the varnish off the valve stems, causing them to 
leak.

The sludge might be all that varnish, washed off and collecting in the pan!

> I guess the lighter components of the oil just found it's way through the
> more worn parts of the engine and away to freedom.

My suspicion is that synthetic oil HAS no lighter components to speak of!  
That's one of the reasons it seems to last so long.  On the other hand, it 
doesn't seem to have any heavy components either -- another possible reason 
it runs through some leaks so readily.  I think synthetic oil is, like, 100% 
medium components.

> I rang Mobil and spoke to their technical department and a "specialist" told
> me that (contrary to all their advertising) an engine over 100,000 miles
> will get no benefit from synthetic oil.  I've written a letter of complaint
> to them and I'll keep you informed.

I've also heard that synthetic oil doesn't do anything for engines that 
weren't designed for it.  Hogwash.  Better lubrication is better lubrication; 
the only question is whether or not your engine will benefit from better 
lubrication.  If it's a Pontiac with 100,000 miles, maybe not, but a Jag can 
always use it!

By the way, my problem with the oil light coming on dropping to idle seems to 
have gone away.  One possible explanation: the zero pressure was caused by 
the relief valve hanging open, either due to scoring or varnish.  The 
synthetic oil cleared it up, relief valve closes promptly as it should, no 
more oil light.

> I could easily afford a number of regular 20W-50 oil changes compared to
> synthetic.

I think one advantage of synthetics is that there apparently are no K-Mart 
synthetics.  The differences between one regular motor oil and another may be 
extreme indeed, but how do you tell which one is acceptable and which isn't?  
If you stick with synthetics, apparently they are all very good.  If, on the 
other hand, you find a regular oil that is truly good, changing it twice as 
often as the recommended interval is probably BETTER than synthetic oil at 
recommended intervals, because you are draining the dirt and contaminants 
twice as often.

>  Or should I stick to semi-synthetic and try to get the best of
> both worlds...

I am not sold on the idea of semi-synthetics.  I suspect you may get the 
WORST of both worlds -- more money than regular oil, but doesn't last any 
longer.

> Re-jigging the oil
> service interval seems a sensible thing to do but the choice of oil and when
> to change the filter will make an impact.  

One of the original claims of synthetic oil was that you could double the 
change interval.  OTOH, it appears to be popular wisdom that you should cut 
the recommended interval in half if you really want the car to last.  
Recommended intervals of 6000-7500 miles are common, but perhaps the carmaker 
doesn't want the car to last too long -- he wants to sell you a new one!  
Recommendations from other sources seem to like 3000 mile intervals, but 
perhaps they are selling oil/service.  Altogether, why I decided on using 
synthetic oil at recommended intervals -- that's cutting it in half, then 
doubling it again.

 -- Kirbert      |     If anything is to be accomplished,
                 |     some rules must be broken.
                 |          - Palm's Postulate

---

References:

• Re: Synthetic Oil
• From: Cosmo <simond@london.informix.com>

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