The analysis method for crude petroleum contained in ASTM D96 or other approved analysis method and as determined by a Customs-accredited commercial laboratory shall be used for Customs purposes if the difference between the value found by the commercial laboratory and the value found by the Customs laboratory does not exceed 0.11 percent. If the difference exceeds this limit and the Customs-accredited commercial laboratory cannot establish that Customs is in error, then the Customs results shall be used.