>
    > I?ve been running Castrol 20-50 in my 20B to this point (about 25
    > hours).  Now that it is about ?broken in?, I?m considering changing
    > to synthetic.
    > Everyone has their favorite oil, but I?m thinking the Idemitsu
    > racing oil;
    > ?specifically engineered to meet the unique requirements of a rotary
    > engine?. http://www.idemitsu-usa.com/page_211.htm, would make sense.
    >
    > It comes in 10-30 and 20-50.  Considering typical operation at high
    > power,about 5000 rpm, and at temps of 180 -210; I?m thinking stay
    > with 20-50.
    >
    > I use the stock oil metering pump for pan oil to the seals.
    >
    > Comments?
    >
    > Al
    >
    > That is what I use in my RX8. Mazda recommends 5 W 30 as I recall.
    > the lighter the weight the less friction and it cools better.
    > Mazdatrix stocks it.
    >
    > Paul Lamar ...No rotor no motor.
    >


   My 2005 RX8 Shinka's manual says 5-20.

   Scott Gettings

   My mistake. Yes  5 W 20.

   Paul Lamar ...No rotor no motor.

That's interesting.  5W 20 sees surprisingly thin..  I would guess,
however, that higher viscosity oils are used where bearing contact
pressure is highest or where a bearing design isn't as good.  In a
piston engine I would further guess that the highest pressure loads
might be in the valve train - where the lifter/tappet rides on the cam,
and where the end of the rocker arm slides across the stem of the
valve..  Anyone have any data on that?

If the above guesses are correct, I can see how the rotary definitely
has advantages.  The ideal case oil on the rotary could be significantly
different as compared to a piston engine.


Regards,

Matt-


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