Ask A Scientist© Chemistry Archive

name        Fadi
status      student
age         20s

Question -  I know that Unleaded fuel and diesel do not mix together...
i just need some scientific facts. I looked over the Internet but i
could not find much. Could you help please.
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Fadi,

Indeed unleaded gasoline an diesel fuel do mix. Both are hydrocarbon compounds
They will dissolve quite nicely in each other. However any attempt to use such
a mixture as a motor fuel would  would be disastrous in either type of engine.

Regards,
ProfHoff
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Actually, they should be able to mix together just fine.  If you put them
into the same container, they will make a single liquid.

However, it is not a good idea to try to mix them together in an engine,
because the fuels are furmulated to different specifications.  Diesel fuels
are designed to easily ignite under conditions of high pressure at moderate
temperatures, because a diesel cylinder fires simply when compression heats
up the fuel-air mixture.  In a gasoline engine, on the other hand, the
fuel-air mixture is ignited by a spark.  If the mixture ignites
spontaneously from compression in the cylinder, it causes problems with
performance, such as engine "pinging" and "run-on."  So, you can imagine
that putting diesel fuel in a gasoline engine or gasoline an a diesel engine
would not be a good idea.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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