1.8T sludge problem - similar datapoint?

[Mark R]

Mike,
Full rebuild for a 231 is (off the top of my head) what?  About
$30,000?  Our PA-28R-200 (Piper Arrow 200) engine was close to
$20,000.  Thermal rates of expansion/contraction are critical to
engine longevity, especially when air cooled as most aircraft engines
are.

That said, 2 points I'd like to add to your excellent post.  First,
general aviation (GA) engines are much different in construction and
packaging than automotive power plants.  Second, synthetic oil has
come a long way since the first (disastrous) GA applications.  Beyond
that, leaded aircraft fuels contribute more combustion byproducts
(deposits) than unleaded fuels.  These byproducts to the combustion
process become suspended solids in the oil.

I've read the SAE reports on engine performance and longevity using
*modern* full synthetic oiling versus "conventional" oils.  I think
you'll be convinced (like I am) that if you plan on keeping an engine
long term, they are definitely "the way to go" in automotive usage. 
In all of the SAE tests back a few years, wear was reduced, bearing
temperatures (indicative of friction) was reduced, and power was
slightly elevated (due to the above, no doubt).  If I recall
correctly, the original problem with first generation synthetics was
that they tended not to "bond with" (or coat) the substrate (bearings,
etc.).  These issues have disappeared with modern oils from what I
understand.

Your point about proper ramp-up and cool down (thermal stability)
shouldn't be lost here.  For long engine life, it's best to properly
(gradually) warm up the engine and do the reverse for cooling.

Lastly, for your suggestions don't forget engine after-run timers. 
They're quite effective although there is a tendency for carbon
deposits to form at idle in the combustion chamber.  That said, this
shouldn't prove to be a problem with an aggressively driven car..

Best,
Mark Rosenkrantz (SEL, MEL, Instrument Airplane)

On 8/3/05, Mike Arman <armanmik at earthlink.net> wrote:
serve capacity.
> 
> In addition, a cool-down period is needed for turbo engines - Mooney says
> to run the engine at a fast idle for five minutes before shut-down (and if
> you have any idea what an engine for a Mooney 231 costs, let me tell you,
> your hair might be on fire, but you'll wait the FULL five minutes!!).
>