What could a difference in compression between cylinders indicate?

A difference in compression between cylinders can indicate several underlying issues, and one of the most significant factors could involve the automatic compression release or the valve lash.

Compression readings that vary significantly between cylinders typically suggest that something is affecting the sealing ability of one or more cylinders. The automatic compression release mechanism is specifically designed to help with starting the engine and can occasionally lead to discrepancies in compression if it is malfunctioning. Similarly, improper valve lash can affect how well the valves seat, which is crucial for maintaining proper compression levels. If the valves are not opening or closing at the correct times or to the required degree, this will impact the overall compression in that cylinder.

While a difference in compression might indicate issues with piston rings or other components, stating that it always indicates a problem with piston rings does not account for all possible causes. Furthermore, focusing solely on low oil levels or suggesting that immediate replacement of the engine is necessary might lead to overlooking potentially simpler solutions or adjustments that could rectify the issue without such drastic measures. Thus, option B encompasses a broader understanding of engine operation, recognizing multiple influences on compression without assuming a singular cause.