A 2024 Isuzu NPR-HD gasoline 6.6L box truck has white exhaust vapor after overnight startup, a slight coolant loss, and no external leaks. Block-test fluid changes color only after a loaded road test. Compression is within 8 percent, and the cooling system holds pressure for 20 minutes cold. The driver also mentions a recent tire rotation, but no chassis vibration is felt on the road test. What is the best interpretation?
