I bought a small inverter generator, filled it with SAE10-30 oil that shipped with it, taking care to check with the dipstick several times so as not to overfill it (though it did take the full bottle), and then ran it for 5 hours, varying the load, per the manual's instructions. The jar in the photo shows the oil that came out afterwards. Is oil normally that dirty after the initial break-in of these inverter generators?

dirty oil after 5-hour break-in period

  • 4
    This will probably be better on mechanics.stackexchange.com It does seem dirty, but I usually don't drain after five hours. There is oil testing sites where they will test the oil for metal.
    – crip659
    Jan 28 at 15:56
  • Does your motor have an oil filter? If yes, consider changing it too.
    – Criggie
    Jan 29 at 20:10
  • No, it shouldn't do that. I think there are problems with that engine - probably pitting in the cylinder wall or other ring sealing troubles. But put some decent, clear oil in it and try again anyway. Also swill the oil with a bright light on it and see if there's much metal. If it looks like a pot of Storm Grey Metallic basecoat, not good.
    – Phil Sweet
    Jan 29 at 21:12
  • No oil filter on the model I bought.
    – mr blint
    Jan 29 at 21:13
  • @PhilSweet Not sure what Storm Grey Metallic basecoat looks like, but when I swirl it, it's not like it's full of glitter, though there may be a few tiny flecks floating around in it here and there. Not sure if they're tiny bubble. They are tiny, about the size of some fine-ground pepper, but very few and far between.
    – mr blint
    Jan 29 at 21:54

1 Answer 1



Many engines are lubricated with a "grease" or heavy oil which is designed to stick to the machined surfaces until they are properly run for the first time.

You followed the running-in process and this is designed to "flush" that original oil or grease and allow the parts to "bed-in" as well. Most times as bearings, rings etc wear-in there is metal residue that is caught by the filter as part of the running-in process.

So that oil you show looks about right. If you are really concerned then send a sample for testing and send further samples after every 10 or 50 hours of running. Chart the progress of the impurities.

  • Running a second test might show that the colour change is not repeated or as pronounced. Interesting idea, it would be a great way to get people to accept the change of the first oil by making it look dirty.
    – KalleMP
    Jan 29 at 13:07
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    To me, this suggests that you ought to do a really good job of draining this initial fill, before refilling
    – Chris H
    Jan 29 at 13:25
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    Most small 4-cycle engines will tell you to change the oil on initial use, usually after some ridiculously short period (often 10 hours or less)
    – Machavity
    Jan 29 at 14:23
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    @Machavity OP said the instructions in the manual said 5 hours...
    – Solar Mike
    Jan 29 at 14:24
  • 3
    @SolarMike Which is my point. This isn't some one-off requirement. Your answer is good at filling in why
    – Machavity
    Jan 29 at 14:27

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