Much varying information about how to properly feed a four stroke engine exists. Cooper's understands both of the great debates regarding four stroke fuels (castor or no-castor and high-oil or low-oil). With a wide spectrum of blends to chose from for the unique operating environment of these engines, everybody will have their desires satisfied.

A little about the different oils for your four stroke

Cooper's has conducted exhaustive run testing on four stroke engines of every popular brand. We've learned that just a little bit of castor in a four stroke is extremely beneficial without any negative effects. What we mean by "a little bit" is 2% to 4% castor by volume. Properly tuned, our fuel with just 2% to 4% castor and the remaining being synthetic, provided clean crankcases with out rust on the bearings or crankshaft or any castor buildup. The valves were free and a golden brown without any buildup after nearly 100 gallons of runtime.

Extensive runtime with YS four strokes (not the 140 DZ) with 3% castor in the fuel revealed absolutely zero carbon buildup in the valves or castor gumming problems in the fuel regulating system. All internals remained clean and rust free.

What we did find through extensive testing was that castor oil quantities over 4% by volume used in four strokes did promote carbon buildup on the exhaust valve only after a significant amount of fuel was run through. YS engines did exhibit gumming of the regulating system when any more than 4% by volume castor fuel was used and when allowed to sit for extended periods. For this reason, Cooper's will only recommend fuels for your four stroke that contain less than 4% castor oil by volume or our all synthetic blends. 

... and about oil quantity

High oil or low oil in four strokes? Engine manufacturers have been bitten by warranty returns as a result of cheap oil or not enough oil in the fuel. The result is engine manufacturers recommending that high amounts of oil be used, regardless if it is good oil, cheap oil or excellent oil. The bottom line is: Fuel manufacturers, including Cooper's will not warranty your engines, only the engine manufacturer will provide the warranty and it is the user of the engine that must determine the suitability of what fuel is used. 

Cooper's makes an entire line of fuels that meets or exceeds every four stroke engine manufacturers recommendations for lubrication requirements.



Cooper's Four Stroke fuels

"Traditional Formulas" Our fuel for the modeler that wants 18% total oil and has enough castor to protect both the modern two and four stroke engines, but not enough to gum anything up. Our "Traditional Formula" contains 15% synthetics and 3% castor, which is more than enough for all the four strokes out there. They are available from 0% through 30% nitro.

"All Synthetic Formulas" blends from 10% nitro on up to 40% nitro. All these blends contain 18% total all synthetic lubricants to satisfy even the most demanding four stroke engine warranty. The 20% nitro formula contains 20% oil (YS- Saito 20/20 blend)

"Plus Formulas": These blends were developed for the demands of the high performance and competition flyers that wanted a lot more without sacrificing engine longevity. A unique and very special synthetic compound, found nowhere else in the industry, unlocks performance in your two or four stroke engines and exceeds engine manufacturers requirements. Runs cooler and produces more power than the competition. We initially designed the Plus formulas around the needs of helicopters and the YS-DZ engines. Available in 10%, 15%, 20% and 30% nitro contents. All Plus formulas are available with or without castor (Plus-C has a synthetic / castor blend).