Strathclyde, which has 1121 vehicles in its fleet, recorded 185 incidents of petrol being put in diesel vehicles or diesel put in petrol vehicles in five years.
All eight police forces in Scotland were asked to reveal how much the oversight had cost them.
In total £60,000 was spent dealing with the wrong fuel being used.
Lothian and Borders and Tayside forked out just over £5600 each but while Tayside recorded 26 incidents, Lothian and Borders had only seven.
Campaign group Taxpayer Scotland said such mistakes can cost police forces a fortune in cash and resources.
Spokesman Robert Oxley said: "Simple measures such as reminders on fuel caps would help ensure officers don't repeat this kind of avoidable error."