What is diesel fuel?
Diesel fuel is made from hydrocarbons that are derived from crude oil (petroleum) through the refining process. There are hundreds of
hydrocarbons in petroleum. Hydrocarbons include any molecules
that just contain hydrogen and carbon, both of which are fuel molecules that can
be burnt (oxidized).
Petroleum is refined to break apart the complex mixture of hydrocarbons into
various products. To do so petroleum is separated into fractions whose
distinguishing feature is their different boiling points. Typical refinery
products include:
|
Product |
Boiling Range oFahrenheit |
| Liquid Petroleum Gas (LPG) |
-40 -31 |
| Gasoline |
80 - 400 |
| Kerosene, Jet Fuel & #1 Diesel Fuel |
340 - 515 |
| #2 Diesel Fuel & Furnace Oil |
350 - 650 |
| Lube Oils |
650 - 1000 |
| Residual Oil (Bunker C) |
650 - 1200 |
| Asphalt |
1000+ |
| Petroleum Coke |
Solid |
Diesel fuel is heavier than gasoline and contains more Btu
value:
| Product |
Weight Per Gallon |
Btu Value |
| Gasoline |
6.17 |
124,000 Btu/Gallon |
| #1 Diesel (Kerosene) |
6.76 |
135,000 Btu/Gallon |
| #2 Diesel |
7.05 |
140,000 Btu/Gallon |
What fuel should I use in my diesel engine?
When choosing the right fuel for your diesel engine you should refer
to your Operation Manual provided by the engine manufacturer. Generally
speaking, engine
manufacturers typically recommend No. 1 and No. 2 grade diesel fuel as described
in ASTM D 975, which are sometimes referred to as "preferred fuels."
These preferred fuels are distillate fuels and are commonly called diesel fuel,
furnace fuel, gas oil and kerosene. Another class of fuels, sometimes referred to as
"permissible fuels," include crude oils or blended fuels. Also,
biodiesel (ASTM D 6751) has been approved for use in most diesel
engines. Diesel engines will run better and have less maintenance problems
if run on higher grade diesel fuel, however for economic considerations the
end-user must weigh the higher cost of the fuel against the additional
maintenance costs involved. For this reason most diesel engines are run on
the lowest cost fuel available, which has been approved by the local, state and
federal government agencies involved.
Engine manufacturers recommend fuel based on effect on performance, safety in
storage and handling, maintenance considerations and possible harmful effects to
the engine. Engine manufacturers "do not" guarantee fuel, nor do fuel dealers guarantee engines. It is up to the end-user
to use the proper recommended fuel, which can vary greatly depending on
geographical location and government regulations. If in doubt ask your
fuel supplier for an analysis of the fuel you are buying or have one performed
by a competent laboratory. Note: analysis can vary considerably from day
to day as stored fuel tends to lose the lighter hydrocarbons, gain moisture and
form algae as well as undergo many other changes caused by a variety of reasons
mostly associated with atmospheric conditions. Typically, the following
properties are tested to insure the quality of the fuel:
| Property of Fuel |
ASTM Test Method |
Effect on Performance |
|
Flash Point
|
D 93 |
The Flash Point of fuel is not directly related to engine
performance. Flash Point is a measurement used to determine how to
safely handle and store the fuel. Flash Point is the lowest
temperature in which fuel can be ignited. Diesel fuel is typically
assigned a Flash Point of between 100 to 160o
Fahrenheit. Diesel fuel has the identification number NA 1993
(Combustible Liquid) when shipped in the U.S. and UN 1202 (Flammable
Liquid) when shipped outside the states. |
| Water & Sediment |
D 2709
D 1796 |
Water and Sediment can clog fuel filters and cause damage to
injectors. |
| Distillation Temperature (Volatility) |
D 86 |
A more volatile fuel allows the engine to start better and
produce less smoke. Volatility requirements depend on engine design
as well as size, load requirements, speed, starting and atmospheric
conditions. Heavier fuels provide best fuel economy because of
higher heat content. More volatile fuel, or lighter fuels, provide
better performance. |
| Viscosity |
D 445 |
Viscosity is a measure of a fluid’s
resistance to flow. The greater the viscosity, the less readily the
liquid flows. This measurement directly relates to the injection
pump and injector leakage. Viscosity affects fuel spray atomization
(turning the liquid fuel into as small droplets as possible before
combustion) and fuel system lubrication. |
| Ash |
D 482 |
Ash-forming materials can be present in diesel fuel in two
forms; (1) abrasive solids, and (2) soluble metallic soaps.
These solids can contribute to injector, fuel pump, piston and ring wear
as well as engine deposits. The soluble metallic soaps also
contribute to engine deposits, which eventually robe the engine of
efficiency. |
| Sulfur |
D2622
D 129 |
Sulfur content can affect emission control systems
performance, which in turn can increase particulate emissions. Fuel
sulfur is chemically changed during combustion to form sulfuric acids,
which attacks metal surfaces and causes corrosive wear. |
| Copper Strip Corrosion |
D 130 |
This test indicates potential difficulties with copper,
brass or bronze parts of the fuel system. |
| Cetane Number |
D 613
|
The Cetane number is a measure of the ignition quality of
the fuel. Cetane has a direct effect on combustion, but does not
materially improve engine performance. |
One of the following:
1. Cetane index, min
2. Aromaticity, % vol, max |
D 976
D 1319 |
For low sulfur diesel #1 and
#2. Determines the aromatic contents of the fuel. Increases in
aromatic content can have a negative impact on emissions. Limits
have been placed on aromatics to reduce particulate matter (PM) and oxide
of nitrogen (NOx) emissions. |
| Cloud Point |
D 2500 |
A measurement used to determine at what temperature a cloud
or haze of wax crystals appears in the fuel. Cloud point affects low
temperature operation of diesel equipment. The
actual values are determined by the
local climate. |
| Pour Point |
D 97 |
Pour point is
usually required to be 6 oC (10 oF) minimum below
ambient temperature. The fuel's pour point is a temperature below
the fuel's cloud point. Fuel stops flowing below the pour point. |
| Carbon Residue |
D 524 |
This test gives a measure of the carbon depositing
tendencies of a fuel oil and relates to engine deposits. |
| API Gravity |
D 287 |
A measurement taken to determine the quality of liquid
products. Higher API gravities have higher value. Recommended
diesel fuel usually has an API Gravity between 30 minimum and 45 maximum. |
| Gums and Resins |
D 381 |
Fuel instability results in the formation of gums, which can
lead to injector deposits or particulates that plug fuel filters or the
fuel injection system. |
Most of the above properties are covered under ASTM Standard D 975 - Detailed Requirements for Diesel Fuel Oils
last updated in 2002.
| Property |
ASTM Test Method |
Grade Low Sulfur
No. 1-D |
Grade Low Sulfur
No. 2-D |
Grade No. 1-D |
Grade No. 2-D |
Grade No. 4-D |
| Flash Point, o C. min. |
D 93 |
38 |
52 |
38 |
52 |
55 |
| Water
& Sediment, % vol, max |
D 2709 |
0.05 |
0.05 |
0.05 |
0.05 |
... |
| D 1796 |
... |
... |
... |
... |
0.50 |
Distillation
Temperature, o
C 90 % % vol Recovered
min
max |
D
86 |
...
288 |
282
338 |
...
288 |
282
338 |
...
... |
Kinematic
Viscosity, mm2/S at 40o
C
min
max |
D 445 |
|
|
|
|
|
|
1.3
2.4 |
1.9
4.1 |
1.3
2.4 |
1.9
4.1 |
5.5
24.0 |
| Ash %
mass, max |
D 482 |
0.01 |
0.01 |
0.01 |
0.01 |
0.10 |
| Sulfur,
% mass, max |
D 2622
D 129 |
0.05
... |
0.05
... |
...
0.50 |
...
0.50 |
0.10
... |
| Copper
strip corrosion rating max 3 h at 50o
C |
D 130 |
No. 3 |
No. 3 |
No.3 |
No. 3 |
... |
| Cetane
number, min |
D 613 |
40 |
40 |
40 |
40 |
30 |
One of
the following properties must be met:
(1) Cetane index, min
(2) Aromaticity, 5 vol. max |
D 976
D 1319 |
40
35 |
40
35 |
...
... |
...
... |
...
... |
Operability
Requirements
Cloud Point, oC,
max
or
LTFT/CFPP, oC,
max |
D 2500
D 4539/
D 6371
D 2500 |
A |
A |
A |
A |
A |
| Ramsbottom
carbon residue on 10% distillation residue, % mass, max |
D 524 |
0.15 |
0.35 |
0.15 |
0.35 |
... |
A Depends on ambient conditions
The primary characteristics that affect engine operation and performance
(especially in colder temperatures) are: Lubricity, Viscosity, Cetane Number,
Cloud Point, Pour Point and Moisture Content.
Lubricity - This describes the ability of the fluid to reduce the friction
between surfaces that are under load. This ability reduces the damage that
can be caused by friction. Lubricity is an important factor when using low
sulfur fuels. Lubricity can be enhanced with additives, but these
additives should be compatible with additives that can already be found in the
fuel.
Viscosity - The viscosity of the fuel is significant because the fuel
serves as a lubricant for the fuel system.
Cetane Number - The cetane number of the fuel has an effect on the ability of
the engine to start. Normally a cetane number above 40 will permit
acceptable engine starts in warmer outside temperatures. The cetane number
can be modified by using acceptable additives or blending the fuel with a fuel
that has a higher cetane rating.
Cloud Point - The cloud point is the temperature that allows some of
the heavier components in the wax of diesel fuel to solidify. This wax is
an important component as it enhances cetane value. No. 1 diesel is
formulated by removing the wax from No. 2 diesel fuel, which makes it a better
cold weather fuel, but more expensive.
Pour Point - Not to be confused with cloud point, the fuel's pour
point is a temperature below the fuel's cloud point. When this temperature
is reached the fuel can no longer be moved effectively with pumps. When
the flow of the fuel stops the engine will die. The fuel's pour point can
be increased by using the proper additives.
Moisture Content - Moisture takes three forms in the fuel:
dissolved, free floating and settled at the bottom of the tank. Most
diesel fuels contain dissolved moisture, but it can only hold in suspension so
much before the moisture becomes free and dispersed. In colder
temperatures free and dispersed moisture can form ice crystals and plug the fuel
filters. If allowed to settle this moisture will eventually find its way
to the bottom of the tank as water is heavier than diesel fuel. Water separators
and fuel filters are installed to contain this moisture. If water is
allowed to stay on the bottom of the tank movement or pumping action can cause
it to go back into suspension and again become free and dispersed. Proper
maintenance and frequent changes of filters is necessary to insure that moisture
does not become a problem to the diesel engine.
| Clean Fuel |
Water Dissolved In Fuel |
Free Floating Water In Fuel |
Settled - Fuel and Water Separate |
|
|
|
|
|
What do engine manufacturers warranties cover?
Engine manufacturers warranties typically cover defects caused by
"material and/or workmanship" for a limited amount of time. Fuel is
not warranted under any condition. The use of products such as diesel fuel
is at the discretion of the end-user. An engine manufacturer can refuse a
warranty claim based on the use of a fuel that is not recommended for use. If
fuel is thought to be the source of a problem it can be analyzed to be sure it falls within the ASTM D 975 standard. Again,
other considerations may need to be taken into account such as the ambient
temperature at which the engine will operate, elevation, etc. Also, local,
state and federal regulations vary from one area of the country to the
next. It is up to the end-user to use the proper fuel.
Will adding RxP to my diesel fuel void my engine
warranty?
No. RxP is added to fuel at the rate of 780 parts per
million (ppm) or .00078% of volume. RxP is made from hydrocarbons
found in petroleum and does not change the molecular structure of the fuel,
which is a design element of the manufacturing process used to protect the
ingredients and blending method. See http://www.rxp.com/ITS.htm
for a comparison of ASTM approved fuel with and without RxP.