Petroleum Generators Don't Get Tuned Up.
Steps to Reproduce
1. Build a room that is considered as a "power plant" with a petroleum generator in it alongside some others (I was using 1 gas and 3 coal in the same room) 2. Hire someone to Tune up the generators 3. Let them Do their Job 4. You will see that Petroleum Generators never get tuned up
This issue has not been confirmed by a developer yet.