William;
I agree that a straight 40, or especially
50, would be heavy for break-in. But there are a couple of considerations
that are different for aircraft. One is that you don’t just get in
and go. The other is the lubrication requirements of the geared re-drive. My
guideline using the 20/50 (or now 15/50 synthetic) is no high power operation
until the oil temp is 140+F. I don’t find that restrictive. By
the time I fire-up, check a few things, (talk to tower), taxi, do moderate
power run-up checks, and get on the runway; it’s higher than that. But
then, so far I haven’t flown with OAT less than about 40F.
And as in my case (and common) we’re
not starting with a new engine.
Al
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of William Wilson
Sent: Sunday, June 28, 2009 10:51
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Startup
Oil
Straight
40 or 50 is WAY too thick for engine oil. Your engine will have to get
almost all the way to operating temperature before it would get any significant
lubrication at all. Typical break in oils are thinner than usual, not
thicker. When the parts are still seating in on a new engine it is harder
for the oil to get in there so you need a thinner oil to make sure everything
gets lubricated.
When starting up, you always want the thinnest oil you can get, because the
most important . Even in hot weather, on startup, 10 weight is about as
thick as you want. The only reason we don't use 0W50 for everything is
because nobody can make it.
There is nothing really wrong with 20W50 in hot weather, but in cool climates,
it's just too thick. When I used mineral oil* I used 10W30 in spring and
fall, 15W40 in summer, and 5W30 in winter. With synthetic now I just use
5W40 all the time, and now I put zinc in it as well (despite my general
opposition to oil additives, the zinc is just putting it back the way it's
supposed to be).
* disclaimer: in cars, but a rotary engine is a rotary engine
On Sun, Jun 28, 2009 at 7:16 PM, Al Gietzen <ALVentures@cox.net> wrote:
Earlier this weekend the recomendation for a startuo
oil was for a mineral oil, 40W minimum. Is a multi viscosity like a
convetional 20W50 OK? or should it be a straight 40W or 50W?
Thanks,
Joe
Joe;
Are you pre-mixing
2-cycle oil? I think the only advantage of a straight weight oil would be
if you use the metering pump injection as a straight weight may burn a bit
cleaner.
I used Castrol 20/50
for about the first 60 hours with the injection system; then converted to
pre-mix and synthetic. The Castrol 20/50 is an excellent lubricant and
served well. It may be that the seals have seated in more since going to premix
as I seemed to have picked up over 100 rpm static over the last 80 hours.
But I think it’s common to get a peak in power somewhere past the
100 hr mark.
Looking forward to
hearing about your first runs.
Al