Castor Mix

Adding about 3 to 4 ounces of castor will bring the oil content up to

Journal bearing ("bushed") engines like more oil, ball bearing engines like less.

Run the engine too hot and synthetic oil breaks down and doesn't work, potentially damaging the engine. Castor, on the other hand, forms a lubricating varnish.

That nifty lubricating varnish that castor forms is a pain and a half to get off an engine -- the fact that the synthetic oil breaks down with heat means that it burns up during combustion and doesn't get your model greasy.

So: castor is safer & dirtier, and if your engine doesn't have ball bearings you need more oil.

IMHO castor isn't going to make a lot of difference until your oil is half castor and half synthetic -- but I'm no fuel whiz.

(and castor smells better).

The ONLY stipulation I would like to add to Tim's comment is that most four strokes can do better with less castor as it tends to gum up the valve stems.

Exactly what I was going to write. That is exactly what I do, ( I go with 4 oz) and one of my engines is a Fox that is supposed to have castor; so it works for me. None of my other engines have a problem with the extra oil, but they are all two strokes. You can not have too much oil, in reason, of course.

Jim in NC

So you can have too much oil if you have too much ?

Really old style (iron piston in a steel sleeve, check with a magnet) need up to 29% oil (Fox Super Fuel from the 50's and 60's had 29% oil). I have a Veco 29 that has been run for hundreds of hours on high castor fuel since I bought it in 1969 and it still has compression like new, with no noticible connecting rod or bearing wear. If you are running the old engines (or simply want to do all you can to preserve your engine from wear) I would add 16 oz of castor knowing that you will have a smoke trail that looks like an aerobatic plane doing their thing.... but as someone else said 3 or 4 oz will help protect the motor even on current engine designs. Do not worry too much about engine varnish with 3 or 4 oz in the mix as the synthetic tends to keep things cleaner. Also varnish build up is worst with lean engine runs and most of us are not racing so do not lean engines out all the way. Bob

Wow, really? I never would have thought that an engine would run with that much oil in it.

I think I will take a pint of fuel and add an amount of oil in the proportion that 16 oz. would be, just to see how it works. I won't have time for a month or so, so if I remember to do it, I'll get back here with the results.

Thanks to all for your assistance.

Howard