ORIGINAL: tlojak38
hi. i got my plane together, got a new engine, went to the hobby shop and they gave me fuel with 15% nitro, and 20% oil. now that my engine is broken in, do i need to get different fuel to fly with, or can i use the rest of what i have? also, once its gone, can i change to lower percentages? thanks for any help.
Well You're secret on the engine, however I think you have an OS 40ax and an OS 46.
The fuel will do fine, especially since the engine is "broken in."
15% nitro is the main fuel because relatively new modelers are led to believe they need the high-priced spread so the dealers can SELL the high priced spread.
With today's common engines, mostly developed with a compression ratio for foreign markets where nitro is not availabel, 5% nitro does fine. Most Eurpean fliers find 80% methanol with 20% oil to do just fine. (Required in FAI competition)
One of the biggest fuel frauds that still exists is that the old Cox .049 - .099 need 20-30% nitro to run well. That is fine for competition Free Flight, CL Speed and Combat, however for sport models they do extremely well using 10% nitro and 25% oil with 1/2 castor oil. Small engines need OIL to cool them.
I keep a Fox 19 CL model, now over 25 years running, and 4 Cox .049 models, 10 t0 15 years old, to have fun with kids/grand kids every so often. Never burn a glo-plug, easy starting, and solid running.
In RC I run everything from .40 to 1.10 glow and larger gassers.
The point of all this is that toy airplane commercial markets spread a lot of rumors about what is REQUIRED. Many RC fliers follow the "in" gossip and really have no clue what it all means. Don't pay a lot of attention to such rumor mongering. When you become a hard-core competition flier then you are in another world, so follow what you think that world requires. BTDT too. Have fun!