Kreen and Schaeffer's 131 Neutra, are two great cleaners. However; they are additives, not oil. Mobil 0W40 (was 20.00 on amazon and Walmart) is a great cleaning oil with a lot of calcium. Kreen is the stronger of the two. MMO is another great cleaner.
If you think about, all machines; including humans, get dirty inside and sometimes need a good cleaning.
I'm currently running Kreen and Mobil 0W40 in my Montero to clean a little bit of varnish. Running it for a 1000 miles.
Respectfully,
Pajero!