Just got the email. ALS is used by WIX, NAPA, and possibly others for UOA testing. They are now comparing used oil to virgin oil for fuel dilution. iirc, they used GC testing prior to this change. Here's the email report: " Fuel dilution is determined by comparing the properties of the in-service sample of oil taken from an engine to those of a â€˜new' unused sample of the same oil. To be able to make a quantitative determination of fuel dilution present in an oil sample, it is therefore imperative that accurate information regarding the oil in use is provided along with the oil sample. Manufacturer, Name and Grade on oil/fluid information is required. Grade is essential, without the grade it is possible that potential fuel dilution may not be able to be determined. In this case, the fuel dilution result will be reported as "- -" along with a comment in the diagnostic statement indicating the oil in use information is required. If a sample is received without fluid information, the fuel dilution result may be reported as "- -". If the missing fluid information is provided within one week after reporting, a request can be made to have your sample re-evaluated and re-reported. This change is being implemented so we can provide you with accurate data for your system. Contact your local laboratory for more details."