Fuel sniffer is a portable fuel dilution meter that can be used in the laboratory or in the field to provide rapid and accurate measurements of fuel contamination in engine oils. It is small in size and ideal for field or laboratory use. It is rugged and easy to operate. It does not require any chemicals and consumables. It needs just over 60 seconds to perform each measurement. It employs a surface acoustic wave vapor microsensor to measure the concentration of fuel in used lubricating oil samples by sampling the headspace in the sample bottle.