The pump at like every station that has diesel says “diesel no. 2.” What is Diesel #2, and is there a Diesel #1 (or #3)?
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Kerosene, Jet-A, furnace oil, and diesel fuel are all “middle distillates” (longer chain/higher boiling point than gasoline, shorter chain/lower boiling point than motor oil), but there are a few differences.
Jet-A and #1 diesel are pretty much kerosene, except they’re less pure than what you’d buy for an oil lamp that would be used indoors. #2 diesel has longer chain aliphatic hydrocarbons (saturated fats) than #1, which gives it the following differences from #1 diesel:
– Better lubricity, so the high-pressure pump doesn’t wear as fast. Truckers frequently add a lubricity improver (one of the functions of a commercial product called Howe’s Diesel Treat) in winter. If you read about diesel aircraft engines, or “yellow gear” that burns Jet-A (one less fuel to stock), it’s common to add a lubricity improver.
– More energy per gallon (better fuel economy).
– Higher cetane rating (measure of a fuel’s tendency to reliably self-ignite when sprayed into air heated by compression), engines start easier.
– Higher cloud point (wax crystals start to precipitate out, making it cloudy), cold filter plugging point (wax crystals are big enough to clog fuel filters), and gel point (fuel turns from liquid to gel). This is the big drawback of #2 diesel, and the reason we don’t use it exclusively.
You may run into the term “reefer fuel”. This is diesel which has not had road excise tax paid, so it’s cheaper. It’s also illegal to use to power a vehicle driven on public roads, but it can legally be used to power refrigeration units on trailers/containers (those engines don’t move the vehicle), off-highway vehicles (such as farm tractors), or as furnace oil. It will usually be the same blend of #1 and #2 that is sold as motor fuel.
In winter, the blend a fuel point sells will have a cold filter plugging point that is slightly below the ambient temperatures expected in the area over the next week or so (the more “winterized” diesel is, the more it costs to make). This can be a problem for inexperienced truckers, since it’s not unusual for a semi to be able to travel 1500 miles between refuellings. Suppose it’s winter, andyou’re assigned to haul a load of oranges from Lotsasunshine Florida to Freezeyerbunsoff Minnesota. You fill up at the company yard, then head to the shipper. It’s about an 1800 mile trip, so you plan to fuel around Chicago a couple days from now. Not so fast! You’re going from warm to cold, so your fuel won’t be suitable for where you’re going. You should fuel every night before your 10 hour rest break (so you’ve got cold-weather fuel in the tanks), and add a good shot of Howe’s. Don’t forget to treat the fuel for the reefer/heater on the trailer – if that fuel clogs the filter, the unit stops, and your trailer is no longer temperature controlled. The consignee will reject your load of frozen oranges. Coming back isn’t a problem, since you’ll be going to areas that are warmer than where you last filled up.
There is also #3 diesel, but you probably won’t run into it. It’s used mainly in large marine diesels, and sometimes in railroad locomotives.
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