BP Ultimate Diesel - specification changed????

[bluey]

BP Ultimate Diesel's product sheet, as currently available from BP website (Issued : 21st February 2008 ) claims a cetane number of min 50, typically 55.
http://www.bp.com/liveassets/bp_inte...o_25022008.pdf

BP Ultimate Diesel's product specification (called product information sheet on the originating web page BP Ultimate Diesel | BP Retail Australia , as currently available from BP website (Issued : 1st May 2010) claims a cetane index of min 46, typically 52.
http://www.bp.com/liveassets/bp_inte...ate_Diesel.pdf

Now I'm confused. Is this the difference between a cetane number and a cetane index or did they change the product specification along the way??

[Diesel_vert]

Cetane number (CN) is a measurement of a fuel's ignition delay.

Cetane index (CI) is a calculated approximation of a fuel's CN. Most sources tend to agree that it correlates well with CN, but since the calculation is based on the fuel's characteristics, there is debate on whether it also reflects the effects of cetane improvers (additives added at the refinery).

So for example, say you have untreated fuel (no additives) with a 'baseline' CN of 46. A calculation of the fuel's CI might also net you a result of 46. Once the refinery adds cetane improvers, that might raise the CN by, say, 4 points, so you end up with a final and true CN of 50. However, the CI doesn't change if the calculation doesn't take the effect of additives into account (depending on which study you believe).

That explains in my example above, why the same fuel has a CN of 50 and a CI of 46.

BTW, there is no such thing as a 'cetane rating'.

[bluey]

I asked BP, who advised me that BP Ultimate Diesel no longer contains a cetane improver. It used to but it no longer does.

The current specification for BP Ultimate Diesel is for a minimum cetane of 46, though the typical value is usually around the 52 mark. The BP Ultimate Diesel contains both detergent and antifoam additives but in previous formulations it also contained a cetane improver which it no longer does. The reference to a 50 minimum would have referred to this earlier product formulation and is not current.

So there, there are no premium diesel products on the market in Australia and nothing that meets the 51CN VAG/EN590 specification for DPF-equipped vehicles.

[Diesel_vert]

The European (EN590) and Australian standard for diesel specifies a minimum CI of 46. So the 'natural' or 'baseline' CN of untreated fuel (i.e. prior to additives being mixed at the refinery stage) must be at least 46.

However, EN590 also specifies a minimum CN of 51 - the Australian standard does not (except for diesel containing biodiesel must have a minimum CN of 51). But there is nothing preventing refineries from producing diesel with a natural CN higher than 46. Given the other specifications listed in the standard, such as the maximum PAH limit of 11%, it may in fact be more cost effective to produce diesel with a naturally high CN. Hence why the typical CI tends to be higher than 46 in practice.

You will also find that most, if not all European manufacturers have always recommend (as opposed to require - the distinction is important) diesel fuel that conforms to EN590 - irrespective of whether it is equipped with a DPF. The performance of a DPF is significantly dependent on sulphur content, compared to the effect of diesel with a CN of 46 or lower.

And yes, the maximum sulphur content (10 ppm) is the same here as it is in Europe.

In any case, since the advent of computer controlled fuel injection, the potential variances in CN we are talking about here are easily compensated for, especially in modern engines where its FIE have grown ever more sophisticated.

So, there are no premium diesel products on the market in Australia and nothing that meets the 51CN VAG/EN590 specification for DPF-equipped vehicles.

Nup.

That said, if the Government suddenly introduced a minimum CN of 51, I suspect the refineries are in a much better position to meet that requirement today, compared to say 9 or 10 years ago.

[bluey]

According to a large manufacturer of 2-EHN Cetane Improver 2-EHN - EURENCO, nitro cetane improvers have significant benefits.

Furthermore, 2-EHN is not only used to improve the quality of diesel fuel, but also to enhance the performance of diesel engine, allowing:
- quicker cold startup,
- diminution of engine startup noise,
- reduction in engine knock and wear,
- production of lower pressures resulting in smoother performance,
- decrease or elimination of carbon build-up on injector nozzles,
- better fuel economy and engine life.

So why did BP remove the nitro cetane improver from Ultimate Diesel?????

[bluey]

The paper "Fuel additives and the environment" from the special task force of the ATC (the Technical Committee of Petroleum Additive Manufacturers in Europe) talks about benefits of cetane improvers:

(b) Purpose
Whilst cetane number is defined in terms of the ease with which a fuel ignites, cetane quality impacts directly on many aspects of engine performance. Engines operating on fuels with a low cetane number are difficult to start, especially in cold weather, noisy, emit high levels of white smoke and hydrocarbon pollutants at start up, produce less power and consume more fuel. High cetane numbers are therefore desirable. This has been recognised by the European legislators who have raised the minimum cetane number of EN 590 fuel to 51.
Aromatics conversion to naphthenes and paraffins through high pressure hydrotreating is a way to achieve higher natural cetane. However this process is very expensive and few European refineries have the necessary hardware to do this today. Cetane improver additives offer a more cost effective way to achieve higher cetane numbers. They can also help to improve refinery profitability by allowing more naphthenic crudes to be processed, and a higher percentage of low-value cracked components to be used in diesel blends.

www.atc-europe.org/showdoc.asp?doc_id=210

This PhD dissertation from 2009 talks about increased NOx emissions related to 2EHN. That might be what scared off BP. Should be not a problem in modern vehicles with NOx catalysts, but would be a problem in older vehicles. The research paper was problematic in that the study used singular 2EHN additive in a research engine with researcher-determined EGR rates and found evidence of injector fouling which has not been noted elsewhere in the literature, and which also made emissions worse.

FUEL PROPERTY IMPACT ON A PREMIXED DIESEL COMBUSTION MODE by Andrew M. Ickes
deepblue.lib.umich.edu/bitstream/2027.42/62369/1/aickes_1.pdf


Specifically, I was trying to find the results from the study "The Effect of 2-Ethylhexyl Nitrate Cetane Improver on Engine Durability" The Effect of 2-Ethylhexyl Nitrate Cetane Improver on Engine Durability. The Ickes paper mentions the durabilty study finding reduced combustion surface deposits and reduced injector fouling, but that in an old engine without EGR. It is expected than reduced engine noise would be associated with reduced mechanical loadings and therefore some less engine wear.