Fuel Mixture Calculator

Many times I am unable to buy locally the specific fuel blend that I want and am either forced to mailorder or drive some distance to another hobby shop. However, my LHS does carry some blends that I can mix and add enough castor oil to suit my needs. The downside was that I spent some time calculating how much of each fuel to use and how much additional castor oil to add. Since I seldom mix up more than a quart at a time for 1/2A flying, I have put together a simple "What if" spreadsheet that allows you to enter varying amounts of two fuels (total must be less than 32 ounces), then gives the number of ounces of pure castor to add to yield one quart of fuel and also returns the percentages of nitro, total oil and castor oil.

Should you want to use only one fuel mix and find how adding castor oil will change the nitro/oil blend percentages, just the set the amount of Fuel B to zero.

If you have a bottle that is marked at the one quart level, add the castor, then enough fuel to bring it to a full 32 ozs. If you are mixing two blends, then you will need to use some other method -- I have a 250 ml. graduated cylinder that works nicely. The conversion is approximately 30 ml/oz.

The spreadsheet has some figures already added, but you may change any value in the light blue cells to match your needs. Two blends are represented: Fuel A is 25/18 with a synthetic/castor mix of 95/5; Fuel B is 15/16 with a synthetic/castor mix of 80/20. Enter a value in the Fuel (oz) cell and arrow out or hit Enter to invoke the change.

The link will launch Excel -- if you want to move the spreadsheet to your local machine, just choose FILE --> SAVE AS and save it wherever you please. It's not Rocket Science, but it may save you some time and give you a little better handle on what your fuel mix is -- and it's free.

Fuel Mixture Calculator