In this paper, new test results in the use of electrochemical techniques to measure corrosion in extended life engine coolants are presented. Corrosion protection performance of the engine coolants (including both fresh coolants and simulated used coolants) for typical cooling system metals under heat rejecting surface and heat accepting surface corrosion conditions for both general corrosion and localized corrosion are measured under conditions similar to the ones encountered in vehicle engine cooling systems as a function of immersion time. Fleet test of the coolants were also conducted. They are used to provide technical support on the electrochemical test methodologies adopted. The effective use of electrochemical techniques to aid the development of the next generation of extended life coolant technologies with improved corrosion protection performance and a longer service life will be demonstrated and discussed.