BF Exclusive: Is US Diesel Fuel Quality a Concern? BMW Responds

We were recently asked to comment on a 2009 common position statement (PDF) from the Diesel Fuel Injection Equipment Manufacturers targeting US diesel fuel standards. The manufacturers included are: BOSCH, CONTINENTAL, DELPHI, DENSO and STANADYNE. They all produce fuel injection systems for cars used in the US. BOSCH is of course the most notable for us BMW enthusiasts.

The paper discusses the use of bio-diesel, Ultra Low Sulfur Diesel in the US and other fuels throughout the world with diesel fuel injection systems.

The alarming piece of information that came out of this paper is that the lubricity of ULSD does not meet these manufacturers’ minimum requirements. So is the US fuel not up to par and did BMW over look this?

Lubricity is determined by a standardized procedure using a High Frequency Reciprocating Rig test. This test method measures the ability of a fluid to affect friction between, and wear to surfaces in relative motion under load. A ball bearing is rubbed on a metal plate and the scar is then measured.

In ULSD further hydroprocessing removes sulfur and significant amounts of polar and aromatic compounds that give conventional diesel fuel adequate lubricating capability. Low lubricity in diesel fuel can cause engine problems unless treated with additives.

The joint statement notes that their standard for lubricity of fuel is 460 microns (HFRR). The US maximum standard is 520 microns of lubricity for ULSD. Thus there is a possibility that the US ULSD would not be within the range recommended by the manufacturers. The paper notes that the use of additives without known negative side effects are recommended to meet these lubricity requirements but that any problems with the engine caused by
the use of an additive is the responsibility of the additive
manufacturer (Would this be an easy issue to prove?). They go onto say: “Refer to the vehicle manufacturers Limitation of Use documentation”; (Owner’s manual).

This posed the question: “What do I do?” to some diesel owner’s as this paper recommends one thing and the BMW owner’s manual says another.

This paper in the end defers to the vehicle manufacturer, BMW and so did we. We asked Dave Buchko, Advanced Powertrain guru at BMWNA corporate communication for an answer to this question.

“BMW, as the vehicle manufacturer, is responsible for certification, compliance, durability, and performance. We must certify the vehicle for at least 10 years and 120,000 miles. The fuel used for
diesel certification is EPA-regulated Tier 2 fuel and must meet certain minimum requirements. If there was a need for an additive, it would have shown itself during that process. Introduction of
additives (except our recommended diesel exhaust fluid) may cause problems with our catalysts, etc. and cause in-use problems.

We’ve been watching US fuel quality very closely for some time. In fact, we worked with fuel companies on the establishment of the top-tier fuel standard. Our monitoring of fuel quality has influenced many decisions, including the decision to bring clean diesel technology to the US.”

BMW does some of the most severe testing by a vehicle manufacturer. While to some consumers it sometimes does not appear that way, in this case they have done their due diligence and have extensive testing to support their recommendation of ULSD and not using additives.

With the complex emissions systems in these BMW Advanced Diesels there is no way of knowing how additives will effect them as they have not been tested by BMW or the additive manufacturer. These are not the diesels of the past using mechanical injection which some of these additives are designed for.

In the end the consumer has the final say but we highly recommend following BMWs recommendations on this one and just filling the tank with ULSD.