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Tussle over lube mark

28th November 1996
Page 14
Page 14, 28th November 1996 — Tussle over lube mark
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by Charles Young • Oil companies and engine manufacturers are arguing over an agreed standard for the lubricity of the new low-sulphur diesel, following concerns that it might be causing premature wear to fuel pumps and injectors.

From 1 October 1996 the statutory maximum sulphur content in diesel was cut from 0.2% to 0.05% This was to reduce particulate emissions but it also affects fuel's ability to lubricate injection systems—pumps and injectors do not have a separate lubricant supply.

The CEC Auto Oil Programme, which includes representatives from major oil and engine companies, is trying to come up with a standard for lubricity although both parties are keen to play down the problem—wary of admitting any fault with their product.

Lubricity is measured by the High Frequency Reciprocating Rig test (HFRR). This produces a wear scar which can be measured. The lower the wear scar the higher the fuel's lubricity. The oil companies are pushing for a figure of 450 microns whereas engine manufacturers want 400 microns. As yet there is no conclusive answer as to which figure is sufficient to protect the fuel pump and injectors.

The first concerns over low-sulphur diesels arose five years ago when lowsulphur fuels went on sale in Sweden. It soon became clear that the low lubricity was causing terminal fuel pump damage. And although the Euro-2 diesel is different, tests run by Esso show that the current low sulphur fuel without additives could cause a vehicle to fail the MoT smoke emission in as little as 84,000km (53,000 miles). Most oil companies are currently using additives to bring the lubricity to around 450 microns. But there are variations. In a recent test of 21 German diesels—Germany has had low-sulphur diesel since 1995—nine had lubricity below the norm for 0.2% sulphur fuels.

Of the operators CM spoke to, none reported problems with Euro-2 diesel although most were aware that there could be a problem.

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