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ISO Specifications for fuel deliveries

ISO 4259:1992 provides for the systematic evaluation of the validity of a given result and assumes that the sample being analysed is a ‘’representative’’ sample of the product delivered/received. Clause 9 of ISO 4259:1992 further establishes a means for the technical & statistical interpretation of ISO test method results.

First, some ISO 4259 terminology. ISO 8217:1996 tables 1 and 2 specify maximum and minimum limits to the true value of a given property.

Reproducibility of test results

This is the closeness of agreement between individual (test) results obtained in the normal and correct operation of the same (test) method on identical test material but under different test conditions. It is the value where there is a 95% confidence that any good laboratory will report for a given sample value.

To apply the ISO requires knowledge of the precision statement of the test method used for analysing that parameter. If the test result is more than the specification limit plus 0.59 times the Reproducibility, then it is 95% certain that this fuel is off spec. In algebraic terms, the fuel fails specification when:

Test Result exceeds Max Specification plus (0.59 X the Reproducibility) If the specification is a lower limit such as Flash Point, the sign is changed to minus.

True Value

As defined by ISO 4259:1992, true value represents the average of an infinite number of single results obtained by an infinite number of laboratories. Therefore this true value can never be established exactly.

The following Tables are based on the above calculations and contain all ISO 8217:1996 fuel category quality parameters and ISO 4259:1992 interpretative values at 95% confidence level.