What is the best indication of worn valve guides?

The indication of worn valve guides is best represented by high oil consumption. When valve guides wear out, they can allow oil to flow past the guides and into the combustion chamber. This results in an increase in oil being burned during the combustion process, leading to higher oil consumption. This excessive consumption can cause symptoms such as blue smoke from the exhaust and a noticeable increase in the frequency and volume of oil usage between changes.

While low compression readings, rough engine idle, and excessive engine noise can indicate various engine issues, they are not as directly associated with valve guide wear as high oil consumption. Low compression is more typically related to piston rings or cylinder wear, a rough idle may stem from ignition problems or fuel delivery issues, and excessive engine noise can arise from many sources including bearing wear or timing issues. Therefore, high oil consumption serves as the most effective marker for identifying worn valve guides.