Below is a part of the article pinned at the top of this forum, you may want to read it all, and modern synthetic oil is much better than castor.. unless you plan to run the engine over lean.
" Years ago, most fuels had only one oil ,castor. This is still a very good oil with many good but some bad points. Some of its good points; it carries heat out of the motor and gives a good plating action on all surfaces, especially when they’re hot. It also has tendencies to move toward hot surfaces, helping to protect them. A few of its bad points; it burns and sticks to the piston sides and the ring groove and all other parts that are hot enough, and will carbonize the chamber. It will stick rings in their grooves, freeze wrist pins and build up ridges on sleeves. This causes excess friction and heat and will ruin your motor in time.
The alternative to castor is synthetic oil and almost all fuels have these in them; the vast majority has all synthetic. Virtually all fuel manufactures use one type of synthetic; these are normally polyalkylene glycol based oils. They are mostly made up of alcohol started linear polymers , of oxypropylene groups. These are made by several companies and are available in a large range of molecular weights and viscosities.
This group of oils is the modern version of the old Ucon oils and also have good and bad points. Some of the goods points; they are very good lubes without containing any wax; they have outstanding load carrying capacity, film strength, anti-wear properties, are resistant to sludge formation, and will help keep your engine clean. The bad points are they give no rust protection by themselves, they don’t plate hot surfaces as well as castor and they burn at high heats.
As you can see, both oils have advantages and disadvantages to them; it’s for these reasons that they work much better blending together than they could ever work alone. Throughout many years of flying ,testing and other research have proven this to me beyond any doubt; plus you can see this for yourself. Recently, a friend of mine had a motor that would go into the pattern and lean out and act very inconsistently. The only change that was made was to substitute one tank of my fuel in the model. The results were drastically different; the motor now ran very smoothly, going into a two cycle instantly when the nose was raised and back into a four cycle instantly when the plane was leveled. This was tried back and forth both fuels; his and mine. The results were the same every time. I see this type of thing happen much too often, and it is extremely frustrating for Flyers to deal with. They often blame these fuel problems on cooling, cowlings, motors ,fuel filters, and unfortunately some don’t have a clue how to recognize or solve this problem. This is a frustration that you can live without!
I would like to tell you there is one Stunt fuel formula to run in all motors, I said I would like to tell you that…unfortunately this is not the case, and will never be as long as we have such a wide range of motors and running styles. What I will tell you is a good formula for the most common types of engines. Make sure you pick a fuel supplier who will give you consistent fuel day to day ,and will blend fuel for your motor needs or has fuel to match your needs. Stay away from any supplier who will not tell you the oil percentage, or who say one type works for all motors. I see this much to often also, It is unfortunate, but a lot of fuel manufactures will try to fool you about the oil and nitro percentage. One trick is to measure by weight and not volume. Doing so, they can claim that the fuel is for example 18 % oil , when in reality it is only 14.9 % oil content. Using weight for ingredient , they can put in a lot less oil and nitro . Other things are changing oil types, going to cheaper Nitro’s, and adding in other types of Nitro parrafins.
So what percentage do you try? For motors like Fox .35s, OS Max 35s or the old McCoy’s and K&B’s, use a fuel with 26 to 28% oil content; preferably half castor and half synthetic, up to 75% castor is OK. These motors have very small bearing surfaces, and are subject to much wear and heat, most are all plain bushing motors and most have unbushed rods. They need a lot of oil to help cool the engines. Since these motors run hot, they need extra oil to keep them lubed,clean, and to carry out heat . If you have one of these that is in very good shape but, is just starting to get some brown or black varnish plating on it, the synthetic mix will clean it up for you, resulting in increased life. Do not use the synthetic blend in an old motor that has a lot of time on it with all castor fuels; the synthetic will remove the castor varnish off the piston and sleeve and will in some cases, leave you with the worn-out motor that had to start with. Also always try to NOT use prop shaft extensions with these engine, as it adds a lot of wear on the crankshaft bearing. "
Topic: 36X BB Break in (Read 3579 times)