2-stroke Engine Oil Content

[Mike Mc]

Getting ready to mix some more fuel and want some opinions on the minimum oil I can use. This is for several ringed engines in the .45 to .90 size. I have a Super Tigre .75 that gets the most flight time. I mix 12% nitro.

 

Just looking to reduce the cleanup. That ST 75 makes a big mess after flying all day with 18% oil.

 

[Peter Jenkins]

ST recommend 5% nitro Mike.  It's cheaper that way as well.  Are you using fully synthetic oil?  You could try asking Motors and Rotors for a recommendation on oil quantity.  Dave Wilshire's dad used to be the ST importer and Dave knows a lot about ST engines.

[Jon H]

Laser 5 with 15% oil should be fine Mike, but Motors and Rotors are the best port of call. 

[Paolo Di Marco]

Hi, 

Of course this is a very broad topic, and experiences may be different, so I am not saying these are "truths"

just my feedback, regurarly flying ST (40 years) since they are very popular here in Italy.

My current ST running on planes:

.60 ABC   with 0%nitro and 16% oil (half castor half synthetic).

on .06-.15 (g29-x11-G20/15)  use 20% oil (half&half) some nitro only on X11 (7% is absolute max, otherwise it will overheat).

 

If I were you I'd try lowering a bit oil content (15%-16% range) with some synthetic -castor blend, I would try an exhaust silicone deflector  to keep the plane cleaner.

Nitro is usually  useless on ST of this size if all rest is ok (tank position, carb setting, etc...), my .60 has a wonderful quick carb transition with 0% Nitro

15% Nitro could give overheat on some application. On ABC engine you can lower a 2% more the oil if you wish 

 

I always set the high speed needle a tad rich.

Regards,

 

Paolo

[Mike Mc]

Thanks,

I was looking for someone who had actual experience with using 14-15% oil. 

 

Do ringed engines need more or less oil. Probably the same. I expect that the rod bearing is the most critical. Have not had the backplate off my ST75 or 90. Do they have bushings on the rod or just aluminum?

 

 

[Engine Doctor]

ST engines have bronze bushed rods. They should run perfectly well on 15% oil .