Generally, it is not a good idea to let an engine reach high RPMs when it is cold. The potential issues with a cold engine under full throttle are well documented.

I have a Fusion Energi and the car works in EV mode until the battery is depleted enough, but it can use the gasoline engine when it needs more power. What I notice happening is I drive for several miles until I reach a significant incline and the gas engine kicks in to help it up the hill. Since it has a sudden need for power, it turns on and immediately revs high. Given the electric motor has a separate cooling system, I do not believe the gas motor has a chance to warm up at all, not to mention having operating temperature oil, when it has been off up to that point in the drive. Unfortunately, this happens basically every day on my commute, it is not rare.

Can this damage the engine or reduce its life significantly?

I could let the car drop by about 10 miles per hour on the incline by staying in EV mode, but I risk causing a small case of road rage behind me.

  • 1
    I am sure the engineers took that in consideration when designing the engine.
    – Moab
    Commented Sep 30, 2020 at 18:51
  • @Moab, I am sure they did as well, similar to how they engineer it to stop/start frequently through starter motor trickery. If someone knows what measures they took to allow the engine to rev so high right from a "cold" start, I would be interested to hear it. One possibility is that the coolant is warmed and circulated, even when the engine is off, through electric heating. I only was able to find information about electric heating for the cabin though. Even that would not help the oil temperature though, I would assume. Commented Sep 30, 2020 at 19:09
  • The best way to warm up a normal cold engine is to run it under moderate load, not to sit there revving it. There is no reason I know why the engine in a hybrid should be any different. If the systems are automatic, why care? As always, don't work a cold vehicle hard, just give it a regular load. I had an Audi automatic once, it would refuse to change into the highest ratio until the engine had warmed up, i.e. it was revving higher than usual. I am sure the engineers know their job. Commented Sep 30, 2020 at 19:58
  • @PoissonFish Probably 0w20 oil spec.
    – Moab
    Commented Sep 30, 2020 at 19:58
  • 1
    @GdD, agreed, but I would rather the engine rev lower for longer than max out for the duration of the hill. Commented Oct 1, 2020 at 15:07


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