COLD FILTER PLUGGING POINT (CFPP)
Page 44
If you've noticed an error in this article please click here to report it so we can fix it.
British Standard –15°C Last year's average –15.22°C This year's average –18.9°C Failures none All makes easily passed the key test for the resistance of diesel to waxing and clogging of filters at low temperatures. Esso came top with –23°C, closely followed by Gulf (-22°C) and Q8 (-21°C). This is a marked improvement on last year where all the samples registered between –15°C and –15.5°C. Jet scored the lowest CFPP with –16°C, still within the British Standard of –15°C.
CLOUD POINT
British Standard none Industry recommendation –5°C Last year's average –6°C This year's average –5.1°C Cloud point measures the cold flow properties of diesel by indicating the point where crystals, which eventually form wax, begin to appear. The samples from Q8, BP, Gulf, Burmah and Fina failed to reach the industry recommended minimum — last year all brands made –5°C. This year's leaders were Elf and Mobil at –7°C, followed by Shell and Total, –6°C.
FROTH VOLUME
British Standard none Last year's average untested This year's average 525m1 Frothing is one of the worst characteristics of diesel. There is no industry recommendation or British Standard. However, our test, carried out by passing a set amount of air through a 190ml fuel sample for 10 minutes, then measuring the foam, did reveal some surprising differences. Top came Q8 which produced 360m1 of foam, closely followed by Esso and Gulf (400m1) and Texaco (420m1). A cluster of samples fell between 480 and 550m1. Gulf and Jet both registered 700; Fina came last with 800m1.
SULPHUR CONTENT
British Standard 0.30% Last year's average untested This year's average 0.27% Failures Mobil/BP With increasing concern over emissions, Commercial Motor decided to introduce this new test into our diesel survey. The British Standard limit is 0.30% of mass — but unlike petrol standards, this level is not legally enforceable. Mobil came bottom in the test with 0.33%. BP also failed to meet recommended levels with 0.31%, and Fina just made it at dead on the 0.30% limit. Best in the group was Burmah with 0.23% followed by Esso and Jet which both registered 0.24%. The remaining samples all contained between 0.25 and 0.26%. All fuel companies will be forced to reduce sulphur levels in diesel during the 1990s.
CETANE INDEX
British Standard Minimum 46 Last year's average 51.64 This year's average 49.33 Failures none The ease of ignition of dery is shown by the cetane index, calculated from the density and distillation of the diesel. The higher the cetane index, the more energy the fuel releases when burned. The cetane index average fell this year: in 1990 the lowest cetane index registered was 50 — this year less than half our samples reached that figure. The best were BP and Shell, which both scored 51. The worst was Mobil which registered an index of 47 — just ahead of the ETA and RHA's recommended minimum.
CONCLUSIONS
Although there has been an across-theboard improvement in the CFPP, it was offset by falls in cetane index and cloud point compared with last year's results. We were also concerned by the high levels of sulphur — some brands were above the recommended British Standard.
No "one-shot" survey of this nature can be definitive: but the 12 samples gathered from round the country were all bought from roadside filling stqlons and could have been used in any operators' vehicle.
The samples were all tested by fuel analyst Caleb Brett International.
We have come up with a league table using a points system. Each brand has been given marks according to its place in each category — the lower the number of points, the better its overall performance.
The top position goes to Esso. Although its diesel samples came fifth in the cloud point test, in every other category it was in the top three. It had the best cold filter plugging point and was second in the sulphur and foaming tests.
Second place goes to Elf — another brand which has improved its performance from previous surveys. Elf had the highest cloud point and came second in the foam test. Its worst performance was in the CFPP test where it came seventh.
Third-place Shell performed well, achieving the highest cetane index, but was let down by its sulphur content and foam content, in sixth and seventh places.
Fourth and fifth places go to Q8 and Total respectively. Q8 performed acceptably in all the tests, but was let down with a cloud point of just –4°C. Total took ninth place in the foam test.
Next came Texaco, which hovered round the middle of the table in all the tests. Burrnah, in seventh position, suffered from a cloud point of just –4°C.
Eighth place was a tie between BP and Gulf. BP also had a poor cloud point of –4°C and a high level of sulphur. Gulf, which had one of the best results in the CFPP test, suffered from high foaming.
Tenth place surprisingly went to Mobil — the winner of the 1990 and 1989 survey. Mobil turned in the worst sulphur result and was bottom in the cetane index table with 47. Eleventh-placed Jet met all the British Standards but did badly in the foaming test. Fina came twelfth; it was last in the cloud point and foaming tests.
For a dispassionate view on our results CM consulted Graham Montgornerie, the FTA's chief mechanical engineer.
He says that while it is nice to see that the oil companies are maintaining a cloud point of –5°, the survey raises two questions: "Why the substantial rise in sulphur content? And why are some fuels above the 0.3% maximum specified in BS2869?
"The present limit for sulphur as specified in BS2869 is 0.3%, but this will need to be brought down to 0.05% by the mid nineties." The average sulphur content for all 11 refineries in the UK has been around 0.2% between 1985-89 inclusive so I'm at a loss to explain the substantial rise in CM's test results. "The fact that the sulphur level is not yet being reduced is not the problem it might appear to be as there is little advantage to be gained (in emission terms) by using low sulphur fuels in older engines because they are not designed for it," he adds. "However, if the 1995/96 limits on particulates are confirmed, it is likely that they will require an oxidation catalyst and/or a particulate trap. In this case, low sulphur fuel will be essential if the catalyst materials are not to be degraded."