So, I'm researching getting a Ford C-Max Energi. It fits well with my commute range (approximately 20 miles a day). I understand that after the battery is depleted, a conventional motor kicks on and drive me the rest of the way. Based on my commute times, The conventional motor will only kick on for about 5-10% of my daily driving. Somehow I doubt this means that I will be able to get away with extending my regular oil change interval by 10-20 times it's regular length, as a 30,000 mile oil change interval seems unrealistic in the best circumstances.

So, can someone who knows how this is calculated explain it?

  • This is interesting. I wonder if the engine has an "hour meter" like a piece of industrial equipment since "miles" is no longer a good indicator of the engine usage? Also, I would imagine that the oil change interval is something like "once a year regardless of miles", but I'm interested in seeing some informed answers.
    – JPhi1618
    Commented Mar 29, 2016 at 18:03
  • Yes, the car keeps track of the time the engine has run. It then turns on the idiot light if its time to change it.
    – race fever
    Commented Mar 29, 2016 at 19:01
  • race fever is correct most modern cars keep track of minutes/hours driven in addition to miles driven. Some even keep track of the month like you would see in a BMW.
    – Ben
    Commented Mar 29, 2016 at 21:10

1 Answer 1


As race fever indicated, many modern cars, and all hybrids, will record how many hours the ICE (internal combustion engine) has been running.

It appears the Ford C-max, along with most other hybrids, pass this clock into an 'oil life indicator' (should have called it Oil Indicator of Life, or OIL for short!), which calculates and displays an alert for when you should change the oil.

The indicator is based on factors such as ICE run time, and time since last oil change (meaning it would still recommend oil changes if the ICE is never started, because oil will degrade over time).

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