On Mon, 7 Nov 1994, David Carment wrote:

> OK dumb question why don't we run diesel in our engines? If its is more
> efficient and cleaner then we should all do the diesel thing. (it is used
> to be a whole lot cheaper too). Or is gas somehow designed to be an
> optimal fuel for other (more conspiratorial) reasons.... -- 

No conspiracy.  First off, diesel is definitely NOT cleaner, as any of the
tailgaters in the recent thread can tell you.  In addition, while BTU/lb 
is very important, a factor called "flash point" is also vital.  Alcohols,
despite (or perhaps because of) their lower BTU value evaporate and burn
at even lower temps/pressures than gasoline.  Diesel fuel doesn't.  Your
standard gas engine is actually a high precision instrument that mixes
fuel, air, and spark in very precise amounts at very precise times.  The
standard vacuum on a carb won't even pull diesel, it's too thick.  While a
fuel injector might force it into a cylinder, it won't evaporate fast
enough to be a good fuel/air mix when the spark goes off.  So, no go on
running diesel fuel thru your gas engine (except as a cleaner and even
then it looks like you forgot to install your piston rings because the
fuel/air mix is AFU). The high compression in a diesel engine not only
raises the temp in the cylinder high enough to ignite the diesel/air mix,
it raises the temp high enough (previous to the ignition point) to
evaporate the (relatively thick) diesel fuel in the combustion air. 
Anyone who wants the gorey details, I can supply them, but in essence: 

	Gas works best in cars designed for gas.
	(use the lowest octane rated gas you can, as all 
	gasoline has the same BTU/lb)

	but oxygenated fuels {w/ethanol/MBTE/etc.} *may*
	reduce the amount of pollutants your car spews

	Diesel works only for diesel (or cleaning your engine)

The full bore/no pollution/low cost/high mileage solution is to convert 
your engine to LPG  (run your engine off your reefer), but initial 
cost/fuel availability is a real problem.  LPG has a high BTU/lb ratio, 
burns very cleanly, and you can generally avoid the road taxes on 
automotive fuels.  On the other hand, conversion can cost 1-2 thousand 
US$, and fueling at 3AM is a real problem (try to find an open camp 
ground/hardware store, in January, in Canada). 

					H Steven Dolan
					dworkin@netcom.com