Often, old trees need sympathy. If cars park near to the stem they cause compaction and add a health and safety concern. Provision of a low fence can prevent these problems. A fence can be a simple post and rail type, or large logs/stems, or even a hedge.
During the recent droughts, many trees have suffered. It is common practice to water newly planted trees. Last summer, I was inspired to water a very dry looking ancient oak. It is not always practicable, but every little helps.