What is the purpose of an oil cooler bypass valve?

• A. To bypass the oil cooler when oil temperature is high
• B. To always keep oil cooler offline
• C. To filter oil before cooling
• D. To bypass the oil cooler when oil temperature is within normal limits, preventing overcooling and assisting warm-up

Answer: (D)

Oil temperature control is the goal here. An oil cooler bypass valve lets oil either go through the cooler or bypass it, so you don’t overcool the oil during warm-up and normal operation. When the oil temperature is within safe limits, bypassing the cooler helps prevent excessive cooling and aids the warm-up process, letting the oil reach and stay in the optimal range more quickly. If the oil were kept always in the cooler path, warm-up would be slower and the oil could become too cool; if the oil were never bypassed, cooling could be excessive. Filtration and always keeping the cooler offline aren’t the functions of this valve.