Fuel grades for piston and turbine aircraft and who supplies them

01 What separates avgas from jet fuel

Avgas is a gasoline. It burns in a spark-ignition piston engine, the kind that turns a propeller through a crankshaft, and its defining number is an octane rating that describes how the fuel resists detonation under compression. Jet fuel is closer to kerosene. It burns in a turbine, where the flame is continuous rather than cycled, and its defining properties are about energy per unit of mass and how it behaves at cold altitude.

You can tell them apart at a glance at the label and by smell, but the reason they are kept apart is mechanical. A piston engine fed jet fuel will not run long. A turbine fed avgas can suffer from lead deposits and lubrication problems. The separation starts at the delivery, not at the aircraft.

02 Which avgas grades are actually sold

For piston aircraft, the grade found at almost every United States fuel point is 100LL, a low-lead avgas rated at 100 octane. Older airframes and engines were designed around 80 octane and 100 octane grades, and those grades survive in small pockets of the market. The letters and numbers are not decoration: the octane rating tells you what compression the engine can tolerate without knocking, and the second part of the name tells you how much lead the blend carries.

The lead is the awkward part. It lubricates valves in engines designed for it, and it comes out of the exhaust as a fine particulate. That is why you see "LL" on the pump rather than a straight 100. The exact share of the piston fleet still needing lead, and the pace at which unleaded replacements are certified, is not something a single page settles. What matters at the ramp is that you match the grade to the engine, not to convenience.

The table ranks nothing. The engine decides which line applies to the aircraft in front of you.

03 Jet fuel grades and what the numbers mean

Turbine fuel comes in a few names. Jet A and Jet A-1 are the kerosene grades, distinguished mainly by freeze point, which decides how cold the fuel can get before wax crystals start to form and block a filter. Jet B is a wider-cut blend with a lower freeze point and a higher vapour pressure, used in very cold operations. In the United States, Jet A is the common grade; the differences between A and A-1 matter at the flight-planning stage, not usually at the truck.

For military and some special operations there is a separate naming scheme, but the physical product overlaps heavily. The practical rule for a line technician or a pilot is that the fuel grade, the additive package and the truck that delivers it are declared before transfer, and the declaration is what you record.

04 How does fuel physically reach the aircraft?

At a large airport, the fuel arrives by pipeline or by tanker truck and goes into bulk storage on the field. From there it moves by hydrant system, a network of underground pipes with access points at the apron, or by refueller truck that carries its own supply. At a smaller field, the truck and the storage tank are often the same piece of infrastructure, and the fuel may arrive by road every few days.

Whichever route it takes, the last step is the same: a hose connects to the aircraft, the quantity and grade are confirmed against the order, and the transfer is logged. The piece of the system that decides what is allowed to be stored, moved and sold at an airport is the airport's own operating rules and the certification it holds, which is why fuel infrastructure is tied to how an airport is run rather than to the aircraft alone.

05 What the airport side of fuel looks like

The federal page that describes airport programmes groups fuel infrastructure inside a much wider set of responsibilities: financial assistance, planning and environmental review, engineering and design standards, safety and operations, and compliance. Fuel storage and delivery sit inside that last group and inside the standards group, because a fuel farm is both an operational and a design question.

The airport programmes page lists the assistance streams and the regional offices that administer them, from the Alaskan region through the Western-Pacific region and headquarters in Washington. If you want to know which office covers a given state, the page names the states in each region, and that is the fastest way to find the right desk.

06 Do you need a different grade at altitude?

Cold is the variable that changes the answer. Kerosene grades thicken as they cool, and above a certain altitude the fuel in the tanks can approach the temperature at which wax begins to separate. That is the reason Jet A-1 exists and the reason flight planning includes a fuel freeze point check on long sectors. For piston aircraft, the concern is different: avgas does not have the same wax problem, but vapour pressure and detonation margins still respond to temperature and altitude.

In both cases, the grade you load is a decision made well before the aircraft is at the pump. What the ramp does is deliver the declared grade correctly and record it. What the pilot does is decide whether the declared grade is the right one for the flight.

07 Who actually controls the fuel farm on a field?

Ownership varies. A fuel farm may belong to the airport, to an FBO, to a fuel distributor or to a cooperative arrangement between operators. The arrangement determines who maintains the tanks, who tests the product and who is accountable when a sample fails. That structure is not visible from the pump, but it shapes how quickly a problem gets fixed.

The operational layer that sits on top is the airport's certification and its surface rules. Fuel trucks and refuelling vehicles move on aprons and taxiways, which means their drivers fall under the airport's surface operating requirements, the same set that governs anyone moving on the movement area. A fuel spill or a mis-fuelling is therefore both a fuel problem and an airport operations problem.

08 What the pump label does not tell you

The label tells you the grade. It does not tell you the additive package, the batch date, the test history or the freeze point margin for the coming flight. Those come from the delivery documentation, the fuel quality control records and the operator's own procedures. If you are making a decision that depends on any of those, the label is the beginning of the question, not the answer.

09 Where to go for the airport-level rules

Fuel is one thread inside a much larger system of airport standards, funding and safety oversight. If your question is about which office administers a programme, which assistance stream applies or which region covers your state, the airport programmes page carries that map. Start there, then work down to the airport's own operating documents for anything specific to the field you are standing on, because the grade on the pump is only the last step of a chain that begins long before the hose comes out.

Entity note

The Federal Aviation Administration Airports page is the agency's hub for airport programmes in the United States. It gathers financial assistance streams such as the Airport Improvement Program, planning and environmental topics, engineering and design standards, safety and operations including Part 139 certification and wildlife hazard mitigation, and compliance functions. It also lists the regional airports offices, each covering named states, and links current airport news and resource documents.

10 Where to continue

The pages below take fuel grades for piston and turbine aircraft and who supplies them a step further inside operations and upkeep, beginning with What a Part 135 operator is and how it is structured, then move on to the next trade. Each one names the agency that holds the rule it describes.