That is a new theory Ron. Conventional wisdom has it the motor oil is

breaking

down at the 500 degree F the apex seal operates at WOT. Take another

look

at the chart I just uploaded. 260 C is 500 F. Here is the chart yet

again.

My test on motor oil where I cooked it in the oven for 1/2 hour and

Idemitsu's

test confirmed this fact. The other data is we have at least a 1000

hours on

an engine in aircraft service with mixed 2 cycle oil and the rotors and

slots

are slick as a whistle. If you would like to confirm this test it is

easy to do.

Put one teaspoon of oil in a used cat food can and set your oven for 500

F.

Don't take my word for it :)

BTW Mazdatrix now carries Idemitsu oil specifically designed for use
in the rotary. I picked up a case of 10W-30 and replaced the garbage
the dealer put in my RX8 when I got the 15,000 mile service.

Paul Lamar

It just occurred to me that not everyone on here has seen the inside
of a used rotary engine. It is a wonder the seals don't stick long before

they

actually do. The major two day job overhauling a rotary is cleaning the

rotors.

Every body has their own way of doing it and just about every chemical
has been tried. Some will eat the rotor bearings. Here is a picture of
a couple of typical rotors. Here too is the temp distribution on
the face of the rotor. 200 C is about 372 F well above the coking

temperature

of most motor oils.

Paul Lamar

Paul,

Like I said, I'm probably wrong, but I started wondering about this because
in taking apart an engine with less than 50,000 miles I was amazed at how
thick the carbon buildup was.
I happened to know this car was driven mostly in rush hour back and forth to
work with lots of starts and stops.
Another engine I dismantled was owned by a salesperson who was on the road
alot ,mostly freeways. This motor had relativly very little carbon at
130,000 miles. If it had not suffered the classic O-ring water jacket crack
in the center housing, it would have made it well over 200k, I'm sure.
Maybe as simple as just a good vs cheap oil. I don't know.
I haven't tested any motor oils but many baked/cooked on things are cleaned
off by raising the temp. I don't think I'm ready to try a torch on my rotors
though. ;-)

Ron Freier

If one engine used synthetic oil and the other ordinary motor oil that would
account for the difference. Mobile One came out tops in my test except for $10
a quart turbine oil. However Mobile One is not optimized for the rotary
so I have high regard for Idemitsu which is.

Paul Lamar
 
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