Sounds like a syntax error.
Nitro percentage is usually listed, it's expensive and considered the power additive. Sport engines usually work fine with 5 to 15% nitro, though you don't really get to high performance fuel until the 30 or 40% nitro fuels and they go all the way up to 70% nitro.
The oil percentage for typical glow engines is in the 16 to about 20% range, but on the extremes are very low oil fuels 8 to 12% for car motors (very high rpm, low torque) or a very few large Super Tigre (2300, 3000, 3200 series). The other end of the oil for fuel would be for control line (low rpm, high torque) and some really old piston/sleeve metal designs with steel or sintered pistons, they need oil percentages into the mid to high 20's (23 to 29%).
Most likely a synthetic castor blend means that both synthetic oil and castor are used. Typically any label lists the ingredients in the order that they are present, so there is more synthetic than caster in the fuel. But if the label was full disclosure, then it would list methanol, synthetic oil, nitro methane, caster oil, and dye.
The late Don Nix sold a lot of fuel, having produced Power Master for many years. Most of his fuels used a blend of oils to get properties of each. A slightly lean run does less damage to an engine with a bit of castor oil in the oil used. But you can also build up a bit of varnish with castor (which is what it does when over heated). Easy to clean with the crock pot method.
Last edited by HighPlains; 03-15-2014 at 07:09 AM.