Oil changer

An oil changer, comprising:

• first and second oil reservoirs for containing unused and used oil, respectively;
• piping extending from said first and second oil reservoirs to an oil use location such that used oil can be drained from said oil use location to said second reservoir and unused oil can be delivered to the oil use location from said first reservoir;
• an oil pump disposed along said piping for pumping oil from the oil use location to said second oil reservoir through said piping and from said first oil reservoir to the oil use location through said piping, and at least one switching valve disposed along said piping;
• a flow rate meter disposed along said piping for measuring the flow rate of oil through said piping and outputting a flow rate signal;
• and
• at least one air sensor disposed along said piping for detecting the presence of air in the used or unused oil flowing through said piping, said at least one air sensor comprising a switch switchable between an open state and a closed state, and outputting a predetermined signal when said switch is in one of said open state and said closed state, and a float movable between a first position in which said float causes said switch to be in said open state and a second position in which said float causes said switch to be in said closed state, said float having the properties of being floated by oil and not being floated by air, and said predetermined signal corresponding to said float not being floated and the presence of air in the oil;
• and
• a control section for receiving said predetermined signal from said at least one air sensor and said flow rate signal from said flow rate meter, counting a number of flow rate signals from said flow rate meter when said predetermined signal is not output from said at least one air sensor and is not received by said control section, and not counting the number of flow rate signals when said predetermined signal is output from said at least one air sensor and received by said control section.