Final answer:
Tech A is correct in looking for signs of mixing fluids in oil-to-water type coolers. Tech B is incorrect because oil-to-air coolers do not involve coolant, thus mixing of oil and coolant should not occur.
Step-by-step explanation:
When discussing oil coolers, Tech A is correct in stating that for oil-to-water type coolers, one should look for signs of mixing of the fluids, such as oil in the coolant and coolant in the oil. This can indicate a failure in the cooler's ability to separate the two fluids, leading to potential engine damage. Tech B, however, is incorrect in suggesting that for oil-to-air type coolers, one should look for oil in the coolant only. Since oil-to-air coolers do not typically involve direct contact between oil and coolant, there should be no coolant in the oil system. Their design relies on the passage of oil through a series of fins that provide a large surface area for heat exchange with air, hence the mixing of oil with the coolant should not occur in these systems.