From: rod@sadtler.com (Rod Farlee)
Newsgroups: rec.aviation.owning
Subject: Fresh Overhaul & Mobil 1
Keywords: engine overhaul synthetic oil tiger
Date: 6 Nov 92 05:40:35 GMT
Organization: Sadtler Research Laboratories

In <greg.719774315@saltydog> greg@saltydog.dpsi.com (Gregory R. 
Travis) writes about oil for break-in after overhaul:
>You really want to use a straight-weight mineral oil, without any 
>additives (especially nothing with TCP!), for break in.  

Lycoming and Penn Yann recommend Shell 80 (a 40 weight mineral oil
in the red can) for the first 50 hours (or until oil consumption
stabilizes, usually 25 hours or less).  I used it for break-in of 
an O-320 with good results (oil consumption 1 qt/25 hrs for the 
last 300 hours, which if anything may be TOO low for minimum 
cylinder wear?).

But an engineer who runs a large engine overhaul shop disagrees, 
recommending Phillips type M multi-grade mineral oil (and adding
LW-16702 TCP additive in the Lycoming O-320-H) during break-in.

Detailed discussion from his book follows; press N to skip.

-----

"During the run-in period, we want mild adhesion wear to occur on
the surfaces.  Therefore, we desire a 'low quality' lubricant such
as mineral oil.
"Lighter viscosity oils allow more ring contact with the cylinder
wall.  You do not want a thick oil that may prevent contact.  We
recommend that you use a 50 weight oil only when temperatures are 
above 80 F.  This recommendation meets the requirements of Lycoming
Service Instruction 1014K.
"Phillips multi-grade mineral oil type M is the best oil for seating
rings.  Do not confuse it with Phillips multi-grade X/C oil that is
an additive (ashless dispersant) oil.  Quite a few engine shops use
Phillips type M.  A multi-grade mineral oil offers a wide viscosity
range which is important for ring seating since is adapts itself
more readily to the changing conditions that occur during ring
seating.  A multi-grade is thinner during engine start and warm-up.
Multi-grade does not thin out as much as a straight weight mineral
oil at the high temperatures which occur during ring seating.
"Continental and Lycoming recommend an aviation mineral grade oil
meeting MIL-L-6082.  Popular oils are Shell mineral oil (red can)
and Phillips type M.  Do not use these mineral oils in Lycoming
TO-360C-F, TIO-360-C,TIO and TIGO-540 series engines.  Use Lycoming
additive LW-16702 in O-320-H and the O/LO-360-E engines along with
the mineral oil."
- John Schwaner, "Sky Ranch Engineering Manual: Aircraft Piston
  Engines: Operation, Failure, Repair", 2nd edition, 1991, p. 155. 

"What about synthetic oil?  Just as petroleum-base oil replaced
castor oil, multi-grade oil will replace single grade oil.  Synthetic
oil will replace petroleum base oil where the advantages of long
oil drain intervals and oxidation stability are more important than
price.  The natural solvency that allows additives and contaminants
to stay mixed with the petroleum oil is not present in synthetics.
Lead deposit accumulation has been a traditional problem in synthetic
lubricants.  Early synthetic lubricants caused valve and ring 
sticking.  This lack of solvency is one reason we believe Shell
15W50 oil incorporates part synthetic and part petroleum oils.
Unfortunately, this oil leaves greater varnish deposits than does
straight-weight Shell oil and the Phillips X/C oil."  
- ibid, p. 255.

"Lycoming recommends thinner oils than Continental.  This is
generally assumed to be because of the placement of the camshaft
and cam followers high up where they are splash lubricated in
Lycoming engines...
"Continental uses 'full flow' lifters to pump oil to the valve
train.  Later engines use oil squirts on both the intake and
exhaust rocker arms.
"The top end of smaller Lycoming engines are not pressure lubricated.
There exists a lip on the crankcase where oil splash collects.  From
here it gravity flows down the push rod tubes to the rocker arms
where drain tubes return the oil to the crankcase.  Now imagine
starting on 50 weight oil on a cold day.  You may have oil pressure
but that does nothing for the rocker bushings.  The oil must splash
onto the lip.  From here it must flow down the pushrod tubes.  If
you have ever tried to drain 50 weight oil out of a can on a cold
day you know that it takes forever to flow out of the can.  It's
going to take just as long to flow down those pushrod tubes.  To
make matters worse, the push rod tubes are on top of the engine
exposed to all the cooling air flow entering the engine compartment.
"With the wrong grade of oil you might be clear of the traffic
pattern before your top end gets any oil.  Despite what your oil
pressure gauge is telling you."  
- ibid, p. 282.

After the engine fully warms up, the crankcase is filled with oil
mist, much of it from the piston squirts.  This probably provides
most of the top-end lube in Lycomings.  Cold 50W oil does not mist!

-----

Opinion on:  

- Mobil-1 is a waste of money.  
It might last 200 hours, but you want to change oil every 50 hours 
to remove acid, water, and dispersed particles and replenish the 
supply of EP extreme pressure and other additives.  

- Shell 15W50 is a waste of money.
Why pay $8/qt for Mobil or even $3/qt for Shell?  At $1.34/qt from 
my local Phillips distributor I get better lubrication of that 
sensitive Lycoming overhead camshaft, and less cylinder wall varnish. 

- Use Phillips X/C 20W50 in your O-360, or any other non-turbo'd
Lycoming.  It's best.  It's cheapest.  What more could you want?  

Opinion off.
-- 
Rod Farlee, rod@sadtler.com, (215) 382-7800
Bio-Rad, Sadtler Div., 3316 Spring Garden St., Philadelphia PA 19104