I have a Nissan VK45DE engine with some oil consumption issues that I think are leaking valve seals.

What harm will come to an engine if used long term with leaking valve seals other than the increase in oil consumption?

  • Eventually it will destroy the catalytic converter and possibly the 02 sensors, not cheap.
    – Moab
    Feb 11, 2019 at 0:18
  • 1
    Well, cats already fell out, so it looks like that already happen, how does it damage the O2 sensors?,
    – Rob
    Feb 11, 2019 at 0:29
  • excessive carbon deposits on the sensor
    – Moab
    Feb 11, 2019 at 20:23

1 Answer 1


If you mean the seals on the valve stems, basically the only factor is burning oil. I had a 1994 GMC Sonoma with the Vortec V 6 engine. Cheap rubber "O" rings on the valve stems failed at 50 K miles . I sold the truck when it had about 100 K miles and I know the subsequent owner drove many more miles without replacing the valve seals. Oil consumption was not much , but there was a big puff of blue smoke on each start caused by the oil that ran down the stems when the engine was off.

  • Ok, I don't have oil smoke at start unless I have been pushing hard and high rpm engine braking then stopping the engine and leaving it for a couple of hours. And smoke when I back off the throttle after accelerating hard (like at a strip)
    – Rob
    Feb 10, 2019 at 22:07
  • Can't this also damage the catalytic converter and oxygen sensors? Mar 2, 2021 at 3:39

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