Diesel fuels

The #3 on that list is equal to our #2.
As I believe it now goes Kero, #1, #2, #3 now?
ASTME website is a big help on deciphering this.

The diesel fuels were, and still are, divided up into numbers or grades according to the amount of refining done .. the ingredient content of the fuel or oil .. and its cetane rating.
#1 is the highest refined grade, and the bigger the number, the heavier, thicker, and less refined, the oil is.

Caterpillar, in the period from the 1930's to the late 1960's, were always big on promoting the fact that the Cat precom engines would burn nearly any grade of diesel fuel or fuel oil .. and would run happily on #2 diesel .. thus not requiring the more expensive and more highly refined, #1 diesel.
In the 30's and 40's, Cat also had the option of a "fuel oil" kit, which allowed for the burning of the heavier, less-refined fuel oils.
These kits comprised an increased number of filters, plus an oil heating arrangement to warm the heavier grades of oil, to allow them to flow, and be injected satisfactorily.

The ASTM set the parameter for fuel specifications, from the early 1930's, as many oil companies used some wild variations of parameters for fuels.
Up until about 1931, there was no specification for diesel fuel at all. Oil companies could sell you any oily hydrocarbon that flowed satisfactorily, and it was called diesel.

Many wells produced (or produce) light oil that is a highly satisfactory diesel, as it comes, straight from the ground. I recall a friend telling me, when he was working on rigs in Central Australia in the early 1980's, they were running the diesel 4WD's on straight, light, production hydrocarbons from the wells, without any refining.

The heavier oils left from refining gasoline and the diesel grades used to be sold as "bunker oil" or "fuel oil" to shipping companies, because the older ships engines would burn about anything.
Nowadays, the modern ships engines are nearly all diesel, and the demand for bunker and fuel oils has dropped alarmingly, thus creating an oversupply of them.
This is the current position for used engine oils, as they were refined and used as bunker oils in recent years .. but with the huge drop in demand for the heavy oils, there is a huge oversupply of used engine oil. Many furnace operations (brickworks, foundries and metal refineries) have gone over to gas, as well, thus eliminating a market for fuel and bunker oils.

Diesel grade specifications have altered substantially from the late 1940's, because of the changes to refining methods, by using "catalytic cracker" refineries, instead of just using "straight run" well production, crude oils.
Catalytic crackers enable precise specification manufacture, of base fuel and oil products, from any crude .. and then, the addition of selected additives, to improve the fuels specifications and performance.
The parameters for fuels and oils become narrower each decade, as higher performance is sought, and engines become highly technically engineered.

The ASTM definition of the test for diesel is outlined as follows .. "The requirements specified for diesel fuel oils shall be determined in accordance with the following test methods: flash point; cloud point; water and sediment; carbon residue; ash; distillation; viscosity; sulfur (content); copper corrosion; cetane number; cetane index; aromaticity; lubricity; and conductivity."

Sulfur content was, and still is, the biggest "division point" amongst the grades of diesel and fuel oil. Sulfur % in fuel has always been a problem, with high sulfur fuels being extremely corrosive to engine components, and destructive to lubricating oils. Even in the 1940's and 1950's, Cat warned about the need for more frequent oil changes with high sulfur fuels.
The second biggest division amongst fuel grades is its flowability.
The third next grading in the line, would be the diesel fuel cetane number.
There are still 7 grades of diesel and fuel oils specified in the ASTM tests .. but these current 7 grade specifications are vastly different to the ASTM specifications of the late 1940's.
The huge, low speed, ships engines can cope with the high sulfur oils better than the high performance, high speed tractor and automotive engines.

Well I have learned more from this site (i need all the help I can get)
I posted that thread because I was unsure as to what bunker oil was Now I know😄 Thanks drujinin,Ozdozer
One last ? Grandpa farmed with JDs (B,G,70 and a F20) He would fire the B on gas then switch to Distilate where does that fall into the scale?
Ok one more ?😮 The heavier the oil the more BTU/liter?

"Distillate" .. or "California Distillate", as it was probably more commonly known, is regarded as one of the kerosene-type "tractor fuels".
It is not regarded as a diesel fuel, as it had a octane number, and was recommended to be used in spark ignition engines.

These "tractor fuels" were termed "low volatility" fuels by Caterpillar, and the "Dotted Line" (Issue 52) of May 1931, went into great detail discussing, outlining, and supplying test results, for the various "low volatility" fuels, worldwide, that could be utilised in Cat spark ignition tractors.

These fuels comprised a range of descriptions such as .. "lamp oils" .. "general purpose kerosene" .. "lighting kerosene" .. "power kerosene" .. "gas oil" .. and "tractor distillate" ..
Some of these fuels were regarded as highly satisfactory .. others were regarded as marginal.
Those that were marginal, were the lower grades, with poor volatility and poor octane ratings .. and these were extremely difficult to ignite, and often had large amounts of crankcase oil dilution, due to unburned fuel.

Re your ? about, "the heavier the oil the more BTU/liter"? - the answer is, Yes ..

In reading about the disasterous typhoon that sank several ships in Admiral Halsey's fleet during WW II, there was some brief descriptive given about trying to relight a dead boiler. All of the ships ran on bunker oil, but to burn it, they used the steam generated by the boilers to heat the oil prior to combustion. If one boiler was producing steam, they were able to use it to pre-heat the oil feeding into another boiler via cross linked steam lines. All of the ships also carried a reserve of diesel, and could burn it in place of the bunker oil in case of emergency. Presumably, the diesel was used for cold starting a dead boiler.