Bill: I worked for both Shell and Esso hauling both Avgas and Mogas to
various locations throughout Canada. The only chemicals added to mogas are
the various additives that clean the internal engine components (fuel
injectors, carburetors and the like, also octane boosters) much the same as
motor oils (detergent or non). The lack of or amount of these cleaners is
the only difference between the various brands. Many times when one company
is out of a particular product they will get it from the other. Avgas on the
other hand is all 100 octane low lead, that is why the different smell while
burning mogas. Leaded fuels have a slightly sweet smell to them. Avgas is
also very dry if you will and burning straight avgas in an automotive engine
without proper modifications can lead to disastrous effects. In the racing
community it is common practice to cut avgas on a 50/50 ratio with mogas for
added performance. That is the odd smell you experience at most Stock Car
Races. There are engines which can burn straight avgas with no degree of ill
effects, one being the Harley Davidson motorcycle which I ran consistently
on straight avgas for many years with no problems whatsoever. The problem
arises since avgas is "low lead" and these leaded fuels are being done away
with in the near future due to environmental concerns and that is why the
FAA in particular is just now starting to take a long hard look at mogas as
a viable solution, hence the STC.
Doug Rupert
Simcoe Ontario.
