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re: Synths, remove deposits and cause oil use - NOT!
Phil Rose said:
>>THINK ABOUT IT! Synths main selling point is ability to resist THERMAL
>>BREAKDOWN. That means they don't change chemical and molecular makeup when
>>the sh*t hits the frying pan (so to speak). That's positively wonderful
>>for bearings and wear surfaces (like turbos eh!) in a hot engine. It sucks
>>for the combusion chamber 'cause the stuff isn't going to burn and blow out
>>the exhaust, its just gonna get sticky and hang around (deposits).
>Is this your conjecture, or is it really established that synthetic oils
>are not combustible during gas engine combustion cycles?
It's based on what I've seen on a friends Porsche 944s with a new 3 angle
valve job which used so much oil under hard use that it filled the piston
tops with goop. There was no oil smoke coming from the engine (it wasn't
"burning") and there were no leaks. Changing to Castrol dino immediately
brought the consumption within normal Porsche parameters (1/2q in 3500 or
so) regardles of driving style where the synths could go out the exhaust as
fast as 1q in 200 miles and was very dependant on driving enthusiasm.
Similar evidence on a "cry slur" mini van used for towing a large boat
(don't ask) which had terrible knock and lack of power which ended up being
caused by excessive compression due to the buildup of synthetic crap in the
combustion chambers and subsequent ignition retard. "Top end cleaner" and
a steady diet of dino saved that owner an engine rebuild (what the dealer,
of course, wanted to do).
>The fact that
>synth oil has high(er) resistance to thermal breakdown (decomposition) at
>high engine-operating temperatures does not in necessarily imply its
>non-combustibility (to say nothing of plain ol' vaporization.) Synthetic
>oil _could_ burn in the cylinders--even while resisting (better than dino
>oil) "thermal breakdown" elsewhere in the engine. Does it? I don't know.
I don't know either. What I do know is that I have never had any trouble
with any engine running dino. With synths I have had leakage and excessive
oil use - in each case these were solved simply by returning to Dino.
Having said that - I suppose you are right. I also suppose we'll never
really answer all the questions.
So... everyone oughta just use what they want or what works for them.
Like I said before. If you motor "burns" oil at least be aware that others
have experienced problems with synths building deposits. If your motor
doesn't use oil then don't worry about it.
Changing the oil and filter often is way more important than which type of
oil you use.
FWIW - My CQ has always had synth or durablend and I have put 1q in the
2500 miles since I have owned the car. I'll be switching to dino and we'll
see what happens...
Manager, Optronics TAC
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