The 1/4 Fuel Tank Rule, a popular but not widely recognized tip, suggests that drivers should never let their fuel tank dip below the ¼ level, which could cause harm to their car's engine and fuel system. This rule can significantly reduce the chance of stranded drivers and potentially save them significant repairs. However, driving on empty can cause issues that could result in a significant repair bill. The rule is particularly useful if you drive a vehicle with a diesel engine, as restarting the engine requires a complex process involving bleeding the fuel system of air and manually bleeding the system.