Chuck;
A lot depends on the type of
oil you used.....I use Shell Rotella 15/40 in everything from the lawn mower on up....It turns black in less than a thousand miles on every vehicle I have ever put it in,it is a diesel grade
oil and will do it on any vehicle,regardless of mileage......Offers great engine protection though,my last company car had 250,000+ miles and my present one has 170,000+ miles and neither ever used a drop of
oil and have never even had the valve cover off............
Also a good idea to cut open the oil filter and check it out,not a bad idea to do it at the next oil change also....
David