I have a 2010 Hyundai i30cw. It's the FD, 2.0L Petrol Engine variant, Automatic Transmission.

Around five or six months ago I took it to the dealer for a service - they didn't call out any issues, but since I got it back I've already had to refill the oil about four months after the service (their sticker doesn't advise an oil change until 1 year has passed, or 10,000km and I'd only done about 5000km).

I also noticed that where I warm it up on my driveway, it has left a sooty black mark where the exhaust points down at the ground. It's hard to say for sure, but perhaps the mileage has gotten very slightly worse (averaging 9.1L per KM where it used to be 8.9-9.0, however it's possible my foot has been heavier in recent months).

The other day, I left the car idling for literally less than two minutes in a shopping centre car park while I was rearranging goods in the trunk and I saw that was enough time to deposit noticeable soot on the ground. The soot appears dry, not wet with water, and the exhaust otherwise looks normal, minimal, and white.

The car recently passed 300,000kms, I've owned it nearly a year and have put around 15,000kms on it in that time. Before the most recent service, it was not depositing soot.

Is this something I need to worry about and/or investigate further, or is it no big deal? The car otherwise performs just fine, no noticeable loss of power or performance.

  • Which engine is in the vehicle?
    – HandyHowie
    Aug 26, 2020 at 7:46
  • Welcome to Motor Vehicle Maintenance & Repair! Aug 26, 2020 at 17:27
  • thanks @HandyHowie, I added engine details to the question.
    – James D
    Aug 26, 2020 at 23:18

1 Answer 1


Is it actually soot or is it oil? If it is oil and you didn't notice this behavior prior to the oil change, I'd suggest one of two things has happened: Either the shop didn't tighten the drain plug tight enough, or they over tightened it and stripped the threads. If it's loose, you should be able to tighten it without too much of a hassle. If it's stripped, it means a new pan. The vehicle could very easily be left either way by the shop.

  • It's soot... the deposit on the ground is dry and "dusty", and distinctly black. If I swipe my finger through it, my finger picks it up.The exhaust on this model is curved down at the ground and the deposit occurs precisely where the exhaust gasses hit the ground, not in a drip line beneath the output of the exhaust.
    – James D
    Aug 26, 2020 at 23:13
  • 1
    @JamesDecker - No worries. Thanks for the clarification. Soot is usually an indication of running rich, but not from oil. Oil will leave a greasy film. Oil will also clog the catalytic converter pretty darn quickly, at least at the amount you're talking about. Aug 27, 2020 at 0:40

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