High-Quality Biodiesel and Engine Life
To a large extent, the longevity of diesel engines is a result of the lubricity of diesel fuel. Prior to the early 1990s diesel fuel had adequate lubricity to ensure minimal wear on crucial, close-tolerance engine parts. Since about 1993, however, in order to clean up the sulfur and aromatic hydrocarbons in diesel emissions, many of the compounds responsible for diesel’s lubricating properties have been removed.
In March, 2000, Quality Management Systems Manager for Stanadyne Automotive Corporation, (Stanadyne makes diesel injection components for Detroit, International, John Deere, and other domestic companies), Paul Henderson stated the following to the Chairman of the Kansas House Environment Committee:
There have been numerous examples from the field where lack of lubricity in the fuel has caused premature equipment breakdowns and in some cases, catastrophic failures. This problem will be more dramatic as EPA moves to further reduce the sulfur levels in petrodiesel fuel.
–NBB
Biodiesel has far superior lubricating properties to the diesel fuel that is in use today. The table below shows how a very small amount (1-2%) of biodiesel blended with conventional diesel fuel #1 and diesel fuel #2, is effective in significantly adding lubrication and reducing wear. The test performed is known as ‘HFRR’ which stands for ‘High Frequency Reciprocating Rig,’ and is the test used by fuel injection equipment manufacturers.
Frequently asked questions
Does using biodiesel make a diesel engine last longer?
High-quality biodiesel can help extend diesel engine life, mainly through its lubricity. Diesel engine longevity depends heavily on fuel lubricity to protect close-tolerance parts such as injection pumps and injectors, and biodiesel lubricates far better than today's low-sulfur diesel.
Biodiesel also has a higher cetane rating, which makes starting easier and reduces ignition delay. The benefit depends on fuel quality: off-spec fuel, especially fuel high in soap, can do the opposite.
How much biodiesel do I need to blend with diesel to improve lubricity?
A very small amount. Blending just 1 to 2% biodiesel into No. 1 or No. 2 diesel significantly increases lubrication and reduces wear, as measured by the High Frequency Reciprocating Rig (HFRR) test that fuel injection equipment manufacturers use.
Biodiesel mixes with petroleum diesel in any ratio, so higher blends such as B5, B20, or B100 also provide the lubricity benefit, as long as the biodiesel meets quality standards.
Why does ultra-low sulfur diesel cause more engine wear?
Refining out sulfur and aromatic compounds to cut diesel emissions also removed many of the compounds that gave diesel fuel its natural lubricity. Before the early 1990s, diesel lubricated close-tolerance engine parts well enough to keep wear minimal; since about 1993, that has no longer been reliably true.
Diesel injection component manufacturers have reported premature breakdowns and even catastrophic failures linked to low-lubricity fuel. Adding a small percentage of biodiesel is an effective way to restore lubricity.
Will switching to biodiesel clog my fuel filter or damage fuel lines?
It may clog the filter briefly at first. Biodiesel is a mild solvent and can scour out deposits left in a fuel system by years of petroleum diesel, which then collect in the fuel filter, so change the filter after the first couple of tanks.
Over months or years, high biodiesel blends can also degrade natural rubber fuel lines, which may swell and weep. Replacing them with Viton or other synthetic materials, as used in most diesel vehicles from 1993 on, resolves this permanently.
Can poor-quality homemade biodiesel harm a diesel engine?
Yes. The engine-life benefits apply to high-quality fuel. Excess soap is likely the most common cause of permanent engine damage blamed on biodiesel, because it forms ash that fouls engine parts. Leftover catalyst and incomplete reactions can raise viscosity, form deposits, and hurt combustion.
Fuel that meets the ASTM D6751 standard runs properly in diesel engines. Home producers should check each batch for clarity and use simple screening tests such as the pHlip and 27/3 tests.
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