How can a mechanic tell if sugar was added to the fuel tank?

Question

In King Pin (1996), during the first scenes we see the protagonist having trouble with his car, so he takes it to a mechanic.

The mechanic wastes no time spotting the problem. He even dips his finger in the fuel (from the fuel pump or another part of the engine that had fuel) and puts it into the mouth of the protagonist for him to taste the sugar.

It is later revealed that Bill Murray's character poured a bag of sugar into the fuel tank.

The question is: How did the mechanic reach the conclusion that sugar was added to the fuel? If it was sand, it could have been possible to detect because, unlike sugar, sand does not dissolve into liquid.

Was it a common tactic for saboteurs to mix sugar with fuel?

Answer 1

Sugar does not dissolve in petrol (gasolene) and prevent the engine firing. That is an urban myth debunked quite eloquently at Snopes. There are other similar sites saying the same thing.

The presence of particles in the fuel can clog the fuel filter, but sugar is no different to any other substance here, sand for example. As the sugar will not have dissolved, it would not be tasted.

The use of sugar in the scene is just playing on the audience. Playing to an assumed belief in the myth.

Answer 2

There is no question that granulated sugar has no worse damage to an engine than any other granular solid, but there are those who say that dissolved sugar (syrup) will get past the fuel filter and do everything bad that people think powdered sugar will do. I am also somewhat skeptical of this claim as well as sugar burns and only dissolves in water and water does not mix with gasoline either.