I own a Ford Ecosport Diesel Turbo 1.5 TDCI. Every morning when I start the car, I put it on neutral and rev it up to 5000 RPM for 3 seconds then bring it back to normal idling without revving and start my normal drive. The intention is to clear any carbon deposits inside the engine and exhaust.

Is that a bad practice? My car is new and just reached 14000 KM. When I started to do this, my car engine noise became less.

  • 49
    This is probably really annoying for your neighbours, especially if you leave early in the morning. Oct 20, 2018 at 19:30
  • 29
    Wait, you do this to a cold engine? Why would you do that to an engine? Is it a lease? Oct 20, 2018 at 20:05
  • 57
    Yes it's a bad practice, your car is at serious risk of being irreparably damaged by your long suffering neighbours. Oct 21, 2018 at 1:36
  • 8
    That's specifically bad for turbos, even after the engine heats up.
    – jpaugh
    Oct 21, 2018 at 16:59
  • 7
    Do not do this, especially for a trubo diesel engine. The engine block and the oil is supposed to be at operating temperature. The turbo is supposed to be warm. I wouldn't be surprised if this habit over time creates pinhole oil leaks from top gasket or turbo, or cause excessive wear of the turbo. I'd rather let it run on idle for 5 minutes before putting it in gear. Do your revving before you park the car. I actually think revving up above work area on a cold engine block causes carbon deposits because of the cold surfaces.
    – Stian
    Oct 22, 2018 at 10:05

4 Answers 4


Yes, this may be bad. The oil is not yet at the operating temperature, and the same is true for engine parts as well. I wouldn't redline a cold engine with cold oil.

Your intention to clear carbon deposits is justified. But why don't you do this during a drive? That way, the engine and oil have had a chance to heat up to operating temperature.

By the way, are you sure the 6K RPM is the redline for your engine? Sounds a bit high for a diesel.

  • You are correct regarding the rev redline, it is 5, not 6. Thank you for responding. Oct 20, 2018 at 16:31
  • Even 5k sounds like more towards the end of redline and not the start of redline for a diesel engine. Oct 23, 2018 at 6:42

If your engine even has a problem carboning up, you don't clear it at cold start. Nor do you clear it by spinning the engine to redline. "Revving" isn't meaningful to diesel engine performance the way it is to sport gas engines and it doesn't help remove carbon. It's just a rationalization.

To remove carbon, you want the engine working hard for 10-20 seconds. Rack position (think: throttle position) is what is relevant, not RPMs. Do it at normal and sane cruise RPMs, where RPMs are enough for the oiling system to be working well, since you will be putting max load on bearings which float in oil. Idle is the wrong speed for this but high revs is also wrong, since the fire won't be in the cylinder long enough.

I do it on the freeway in top gear, and just go to wide open throttle and hold it until unable/unsafe/illegal to continue. A good place (remember engine must be fully at operating temperature) is one of those curvy entrance ramps where you must accelerate from 30 mph to freeway speed. Start that in the highest gear you can without the engine lugging, and move the gears upward as needed to keep RPM in cruise range and acceleration poor. Poor acceleration equals longer time accelerating, which is what we want to maintain full rack for as long as possible.

Obviously lift off the throttle before you press the clutch to shift. I am assuming stick, if automatic you will find the auto downshifts to help you accelerate harder which is not what you want, and you will find it difficult to keep the RPMs low enough for this to work properly. With an automatic, your better choice is a nice steep mountain grade that demands the engine's all.

We have the same problem in locomotives: the electric transmission is infinitely variable so it's hard to hold full rack in any but maximum power (also max RPM). Fortunately locomotive diesels are built so the published redline (~1000 RPM) is analogous to an automobile's cruise, and they can run there for weeks, i.e. In stationary generator applications. So a nice grade does the trick just fine, and "nice grade" for a RR is is 1 or 2 feet rise per 100' run, barely noticeable to anyone but bicyclists. Grades like that are all over.

  • That was new for me. I thought of clearing carbon by revving which as you mentioned, sounds incorrect. Oct 21, 2018 at 1:59

Please no; don't do that. Use something like "Shell Rotella" with the proper detergents and let the oil do the work - over a long drive.

I'm not sure what oil your owner's manual specifies, but use those oils and drive normally.

3 seconds of revving on a cold start isn't going to "remove" much carbon. You would be much better off with frequent oil changes with an OEM approved oil.

  • I see such similar advise from all comments here... So, I stopped revving on cold start and instead I do a high speed ride everyday to remove carbon... Hope that is fine. Nov 3, 2018 at 7:31
  • @EthicalGamer I think that should be the right approach. I would suggest it's less about the "high speed" and more about the "long time at normal operating temperature". Whatever you decide, revving on cold start is insane.
    – SteveRacer
    Nov 3, 2018 at 7:40

yes, most of the wear occurs the first few seconds of start up.

secondly, your hurting your head gasket. the engine is like a pressure cooker made from a cookie sheet. if you heat the cookie sheet up real fast it warps... warping is bad, let it run for 10 minutes before you floor it speed racer

-racer x

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