@Bob Mazza, I agree with much of what others already posted here - oil stains on the carpet and globs of grease caking walls, stove, floors, etc. is NOT NORMAL WEAR AND TEAR.

Perhaps, relying on the credit reports may not be a great tool after all. time.com/4288093/john-oliver-credit-reports-last-week-tonight/?

Taft is a town of 10,000 oil/ag workers, but it also has a community college and a prison, about 1 hour from Bakersfield. 

For example, no rice, pasta, grease or oil, for these gum up the pipes terribly and bring most disposals to a grinding halt.

Is it the uncertainty of LNG or oil related?

Even the cleanest dogs have oils in their skin and hair, and all carpet will eventually smell of animals in houses that have animals, no matter if they have "accidents" or not. 

Considering I have bought gas, oil, a weed-eater, lawn tools, etc.?

I don't allow oil changes or mechanical work it is only for parking,  your setup is probably suited to something different but I would consider noise hours   If they are in the garage in the night you don't want them blasting the radio.

If the tenant is responsible for heating oil  / propane you have to account for that at move out.  

-slap some outdoor oil-based paint on it, but wait until the 2nd or 3rd time they mention it; again, the tenant accepted the property the way it was.Replace a leaky garden hose.