what is distillate???????

: Distillate is simply the left over parts of crude oil after the more popular fractions have been distilled out! Hence the name.....
: : Basically, you'd take the crude oil and heat it in a still. The different hyrdocarbons in the crude mix will distill out in order of their complexity.
: : Methane (one), Butane (two), Propane (three), etc. All come out in order as gas and are sent to storage facilities at the well sites (usually). The crude oil is a mix of all of the liquid (at normal temperatures) HC chains. If you heat it up, the liquids turn into gas, with the lighter ones boiling off first, followed in succession by the heavier ones. The crude oil in the still will settle out at temperature points, which tells you what fraction is boiling off currently.
: : Now, since you want reasonably pure Gasolene, Kerosene, diesel, etc. you have a point where the liquid in the still is ramping to the next temperature point; you need to dump the output during the ramping into a different container. Once the temp. stabilizes at the next point, you switch the output to the pipes leading to the specific storage tanks (gas, kero, etc.)
: : So, when you're done with this process you have a number of tanks containing specific grades of fuels, and an extra tank containing a mixture of all of the fuels. This extra mixed fuel was referred to as distillate!
: : Now, you wonder where you can get it today? You can't! It hasn't existed since 1943! you see, the oil refining process was forever changed as a result of the Second World War!
: : A process for making a barrel of crude oil into a barrel of gasolene was needed to fuel the war effort. The distillation process was replaced by the cracking process.
: : Cracking involves a catalytic process whereby all of the HC chains in the crude are split in to single HC molecules. Then, these molecules are recombined into the required HC chains necessary to produce a specific fuel (Gasolene, Kerosene, Diesel, etc).

All tractor fuels are "distilled" or burned off from crude oil. The lighter stuff with fewer carbon molecules, like paint thinner, comes off first. Then you get gasolines with 6,7,8,9 carbon atoms per molecule. Then comes the heavier fuels like kerosene (a.k.a. distillate) with 11 to 14 carbons atoms per molecule. Then come heavier fuels like Diesel and heating oil. Then the heavy stuff like motor oil, and asphalt are last in line.

When that distillate tractor was built, there was more demand for gasoline in cars than there was for kerosene - so it was a lot cheaper then than gas. Now that we have turbine jets that burn kerosene, the price has gone up. There's little savings in burning kerosene anymore.

When distillate did mean fuel cost savings, you had to modify the engine to burn kerosene. First it is easier to start on gas than kero, so you see two tank and a switchover valve on the kero engine. Second kero has more carbons per molecule than gasoline - so you have to change the carb / intake to add heat so it stays as a mist and doesn't fall out as a liquid when it's cold - so you had to add ducts to heat the carb/intake manifold. Next and last, kero has more hydrogen atoms per molecule than gas - so it makes a bigger explosion when it does fire. The engine is basically an air pump. So if the amount of explosion is greater, you have to make less pressure in the air pump (called compression ratio in an engine) to compensate.

They used to say better living through chemistry - that may not be true - but different engines from different chemistry surely is.