What might excessively worn valve guides lead to?

Excessively worn valve guides can result in significant engine issues, one of which is increased oil consumption. When valve guides wear down, the clearance between the valve stem and the guide widens. This excess clearance allows oil, which normally lubricates the valve system, to flow into the combustion chamber, leading to burning oil and increased consumption.

The options of replacement and reaming to oversize are also valid considerations in maintenance and repair practices. Valve guides may be replaced if they are removable and the wear is beyond acceptable limits. Alternatively, if the wear isn't excessive, they may be reamed to an oversize to restore the correct clearance with the valve stem.

Considering the implications of worn valve guides—both in terms of functionality and necessary corrective actions—it's accurate to say that all these factors collectively highlight the consequences and possible solutions related to worn valve guides. Thus, recognizing that oil consumption is a critical issue linked to this wear makes it clear why one would conclude that all the provided statements are true.