Performance of a full carboxylate coolant has been demonstrated in engine bench cavitation testing, fleet testing, and post fleet testing coolant corrosion tests. Performance in the proposed ASTM “Heavy Duty Cavitation Test” was established and found to satisfactorily exceed performance limits. Fleet testing of a full carboxylate coolant technology in Class 8 trucks, using Caterpillar C-12 engines demonstrated minimal inhibitor depletion to 400 000 miles under controlled zero coolant top-off conditions with no refortification. In a second fleet, vehicles accumulated high mileages under real world conditions. In this test, Caterpillar 3406E engines were torn down and inspected demonstrating extended corrosion protection and superior component durability to beyond 700 000 miles, without the addition of supplemental coolant additives or extenders. Coolants from these vehicles were removed and tested in the laboratory to verify their extended life properties.