dirty oil cap on 1997 Lexus ES300

I removed my oil cap and it is dirty inside valve cover and cap. What is the cause of this is it going to cause damage?

Asked by for the 1997 Lexus ES300
Lexus changed/shortened the recommended oil change intervals due to a build up of sludge in these engines. Initially the oil change intervals were too long, great engine, change the oil every 3000 miles and should be all right.
1 more answer
This is usually oil sludge and just keep having your oil and filter changed regularly and it should be fine