My dad's '69 318 at 140k got its first change of mobil 1 in 1978 and
promptly burned 3 exhaust valves. About all I can figure is the oil was
thinner and did not conduct heat from the valve stems to the guides as well
or something ... things might be altogether different now, though.
Some people say if you have leaks, the synthetic will leak even more. Maybe
it's because it doesn't have to be so thick at room temperature to be just
right viscosity at operating temperature - it's thin all the time!
I've run synthetic more recently in a 455 Pontiac engine with no issues
noted.
Mike
-----Original Message-----
From: owner-dakota-truck@bent.twistedbits.net
[mailto:owner-dakota-truck@bent.twistedbits.net] On Behalf Of Matt Beazer
Sent: Sunday, May 24, 2009 3:49 PM
To: dakota-truck-moderator@bent.twistedbits.net
Subject: DML: 134k - To Synthetic or not to synthetic?
What's the general consensus on how well the 318 handles being
switched to synthetic oil at 100k+ miles? My '94 has 134k on it, no
real leaks, no oil being burned, excellent oil pressure, at least as
far as you can trust the stock gauge. The only thing approaching a
leak is a slow leeching from the valve cover gaskets that will be
fixed shortly, but it's barely enough to make the top rail of the
heads damp. It's just the standard hardening of the rubber gaskets
from hundreds of heat cycles, which I'll fix when I get around to
buying new gaskets.
Yes, I know that synthetic oil doesn't cause leaks, it just uncovers
ones that already existed but were plugged by crud that gets eaten out
by the detergents in the oil. Still, no leaks right now makes me
happy, heh.
I don't mind replacing a leaking oil pressure sending unit or
something small like that, but if the rear main seal or something
that's a pain to get to like that is going to spring a leak I'll just
have to live with a decent dino juice oil, 3k oil changes, brown
stained engine internals and a smell that makes me want to gag
whenever I take something apart. :)
Thanks,
MattB
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