Which of the following is NOT a likely source for determining the correct power steering fluid to be used in a vehicle?

The owner’s manual is the most authoritative source for determining the correct power steering fluid for a specific vehicle. It typically includes detailed information about specifications, including fluid types and capacities, ensuring that the user can find manufacturer-recommended products. Similarly, a service manual is another reliable source as it contains comprehensive technical data, including fluid specifications, maintenance procedures, and guidelines for service technicians.

Technical service bulletins are also valuable as they provide updates and recommendations that can change over time, especially if the manufacturer recognizes issues with previous fluid specifications or introduces new products.

In contrast, a parts and labor guide primarily assists in estimating costs for repairs and does not usually contain specific information about fluid types. The purpose of such a guide is focused more on pricing than detailing the technical requirements of various components, including fluids. Therefore, when determining the appropriate power steering fluid, this option is the least likely source of correct information compared to the others listed.