(Continued from Part 1. This concludes the article.)
Fuel Restoration Techniques
These suggestions are appropriate as means of ‘last resort’ in an attempt improve a degraded fuel. Another advantage of storing Avgas is that we can blend it with other gasolines to bring up the octane level and to dilute the degraded automotive gas. Dilution is the solution. The combination of non-ethanol unleaded premium and Avgas 101LL can restore the depleted octane level of the automotive gasoline (Mogas) that has lost its octane rating over a one-year or much longer period of time. This blend can bring it back closer to a level that our chainsaw manufacturer recommends as the minimum needed to operate the saw without damaging it. For modern Stihl brand chainsaws, this minimum octane rating is 91. Older generators that are 4-cycle engines are designed to be low compression motors that can operate well on degraded stored gasoline with a reduced octane level.
Very old automotive gas could be blended in small proportions with fresher gasolines, or Avgas to extend our fuel reserves. A word of caution: Do not mix too much of this old gasoline that smells like turpentine in with too little fresh gas, or attempt to use it even if runs the engine after the engine is started with a fresher fuel, as it might cause lacquer to build up on the compression rings and ruin the motor.
If we are desperately low on gasoline, yet there happens to be a few gallons of white gas (Coleman fuel) and we need to run a small generator to charge batteries or a chainsaw, we can blend in:
3 parts 96 octane Avgas (Aviation gasoline) with one part white gas,
or,
4 parts fresh automotive gasoline with with one part white gas.
Fresh Avgas has an octane rating of 96. White gas, 55. As a estimate only, we can ballpark the octane level of this blend of fuels by a simple calculation that roughly gauges the octane level of our fuel blend. Where 1 part Avgas is, then use the number 96. And for 1 part of white gas, use the number 55. To find the average and the resulting octane level of a blend: 96+96+96+55 divided by 4 = 85.75, the approximate octane rating.
And if there is 75% or higher in concentration alcohol available, we can further improve the octane level, by adding enough until the motor ceases to ping, or knock. Because 4-cycle small motors are generally lower compression motors, this blend might be satisfactory. If not, then add a bit more Avgas, fresh automotive gas, alcohol, or toluene.
Instead of white gas, if we only have degraded automotive gasoline to extend our dwindling supply, the same approach can be taken. Of course, the octane level of the old fuel would be unknown and we would have to just do the best we can, and mix in only one part for every three parts of Avgas, or less. If the motor pings or knocks, then we can add alcohol or toluene to further increase the octane level. In the event that we must run this blend in a motor “as is”, only run the motor for short periods and lower speeds, so that it does not become too hot, and create the conditions where there is risk of melting a hole in the piston.Continue reading“Long-Term Storage of Gasoline Fuels – Part 2, by Tunnel Rabbit”
