Hi, Matt; That symptom is very odd, I have to admit. Just opposite of normal. LOL. Only a guess, here, but could the thermostat be sticking open? If so, though, I would think that it would take a long time for the engine to reach normal operating temp?
Mazda 6 55 plate 140k miles full service history. On longer drives 80 miles+ towards end as I speed up 75+ engine temp gauge falls towards cold. Slow down 65-70 temp gauge rises back to normal, speed up drops again. Any ideas why it is doing this please?