Esanger,

Glow fuel is nitro methane and oil, some are made with synthetic oils some are castor and synthetic blends ,and the original was all castor,

it is used because the only way that a glow engine lubricates is from the residual oil, much the same way as a chainsaw does with 4 stroke oil, or a boat motor that requires mixed fuel,

If you have ever been to the drags those cars burn nitro, it burns at a very fast rate when compressed , and that in a glow motor amounts to the high rpms that these little motors produce.

on the other hand gasoline burns at a much slower rate, and requires the spark from a magneto or battey to continue burning ,

and fuel being suppied in much larger quanities to produce a very significantly reduced power per cycle than does glow fuel.

the advantages of gas over glow fuel is cost ,,,,,, a much longer stroke in the engine , making it possible to swing a much bigger prop.

the advantages of glow fuel are , less weight both in fuel and engine , a much higher rpm range , and smaller engine size making it much more versatile in plane size.

Hope this helps a little .