Technically speaking, the engines you are referring to are turbine (not jet). There are two types of turbine engines: turbojets and turboprops. The first ones p

Technically speaking, the engines you are referring to are turbine (not jet). There are two types of turbine engines: turbojets and turboprops. The first ones produce a significant portion of the thrust via jet exhaust (even though high bypass jets are close to prop engines). Even turboprops (like the popular Garrets and PT6's) produce about 10 percent of their thrust through jet exhaust. To be even more technical, the difference between turbine and piston engines is in the combustion chamber: open combustion in the case of a turbine and closed in the case of a piston. Finally, there are turbine engines that run just fine on LL100 (leaded avgas). Garrets, for example. One can even mix gas and jet-A in those. It is not recommended to run avgas for more than 1000 hours though due to potential issues with lead deposits. Some military jets engines are designed to run on almost anything combustible except maybe coal dust (I am exaggerating somewhat, of course).