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Fuel Info

Wrecker

The Oil Geek
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I'll address cetane first.

Diesel fuels are classified 1D, 2D, and 4D. Low speed, stationary units use 4D fuels. 4D fuel is not appropriate for most mobile equipment. On-highway and mobile equipment use 1D and 2D fuels. High speed diesel engines use either 1D or 2D fuels. Important characteristics of diesel fuels are its viscosity, pour point, and cetane number. The primary differences between 1D and 2D fuel are the pour point and the viscosity. As you may know, pour point is the lowest temperature at which a liquid will flow, and viscosity is the resistance of a liquid to flow. A 1D fuel is designed for cold weather operation; thus, it is less viscous and has a lower pour point. A 2D fuel is used in warmer weather because it has a higher viscosity and pour point. The higher viscosity provides better lubrication qualities for the moving parts of the fuel injection system. Because 2D fuels contain more Btu's (British thermal units - the amount of heat necessary to raise one (1) pound of water one (1) degree fahrenheit) per gallon, they are able to deliver more power per gallon. This is critical to diesel engine fuel economy. The higher the Btu rating a diesel fuel has, the greater power yield per gallon; thus, higher mpg will result. Cetane rating is the diesel equivalent to gasoline's octane rating. Unlike an octane rating, which rates gasoline's resistance to spontaneous ignition, the cetane rating number (usually 40 to 55 for medium to high speed engines) notes the relative ease with which diesel fuel ignites. The higher the cetane number, the easier the fuel ignites; the higher the octane number, the more resistant the fuel is to ignition. Each manufacturer usually specifies a minimum or maximum cetane rating and the suggested operating temperature for 1D and 2D fuels. A given fuel may meet 1D or 2D specifications, but if the Btu rating is too low, then decreased fuel mpg will result.

Cetane number should not be considered alone when evaluating diesel fuel quality. API gravity, BTU content, distillation range, sulfur content, stability and flash point are all very important. In colder weather, cloud point and low temperature filter plugging point may be critical factors.

Diesel fuels with cetane number lower than minimum engine requirements can cause rough engine operation. They are more difficult to start, expecially in cold weather or at high altitudes, and they accelerate lubricating oil sludge formation. Many low cetane fuels increase engine deposits resulting in more smoke, increased exhaust emissions and greater engine wear.

Increasing the cetane number alone is not a fix for poor quality fuel. Additionally, increasing the cetane number beyond the engine's requirements will not increase performance. However, the cetane number of diesel fuel is not always consistent and you may desire to use a cetane improver to ensure full performance of your engine. If such an additive is to be used, it must not contain alcohol or other water emulsifiers (per GM).

For those of you running aftermarket or custom tunes, it is difficult to say what your minimum cetane requirement is, it may take some trial and error.

More on (Moron:confused:) the other stuff later, I've almost bored myself to tears, I feel bad for you guys reading this.
 

Wrecker

The Oil Geek
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Next I'll blab about good reasons to use additives besides cetane.

As diesel engines are used, they become less efficient over time. Fuel injector deposits interrupt spray patterns, causing poor fuel atomization, incomplete combustion, excessive emissions and smoke. The net savings on fuel expense can result in no additional cost to vehicle operation.

Cleanliness refers to the absence of water and particulate contamination. This characteristic is important because dirt and water can plug fuel filters in your engine and cause severe damage to your fuel injection system because of the close tolerances within fuel pumps and injectors. All diesel engine manufacturers equip their engines with fuel filters to protect the fuel delivery system. Some manufacturers also provide filters with drain valves and recommend periodic draining of any water that may accumulate from condensation and careless handling in storage or vehicle tanks. It is important to note that there are emulsifiers (water absorbing) and demulsifiers (water separating), emulsifiers are not recommended for modern high pressure injection systems.

Stability is the term used to describe a fuel's resistance to the formation of gums and insoluble oxidation products. Fuels with poor oxidation stability contain insoluble particles that can plug fuel filters. This may lead to decreased engine performance or engine stalling from fuel starvation.

Lubricity is the characteristic that ensures protection against fuel pump and injector wear. Since 2005 the use of lubricity additives has become common for most quality fuel distributors, however this is a bulk add/batch test type of evolution. There are rumors and legends in the industry of lazy/hungover/in a hurry employees doing a poor job of this or skipping it entirely. Injectors and fuel pumps are expensive, protect them.

Using a quality fuel additive will help to mitigate fuel inconsistencies, and maximize your fuel mileage potential.

TBN maximization:
With high rates of exhaust gas recirculation (EGR) in modern diesel engines, acids from combustion are of particular concern. AMSOIL Diesel Concentrate neutralizes acids during combustion. It helps reduce acid caused cylinder wear and helps extend engine oil TBN, maintaining engine oil quality longer for better protection. I don't know if other products do this or not, I have not seen manufacturers claim that they do besides Amsoil. If you are extending your oil drain cycles and/or running a bypass filtration unit, this is a biggie. For those of you with blocked EGRs, not so much.
 

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