Dark Engine oil

[marks737]

Hello. Have twin qsb 5.9 engines. Engine oil is black. I’ve read that this is normal for diesels? I change oil at end of Every season. Is it ok to refresh oil by draining a gal and replacing with fresh oil until end of season full oil change?

Topic

[Francis Valerio]

You are totally OK. The oil gets black very quickly and is NORMAL. 60-75 hrs is no problem and no need to change the oil except the one time for the season in your case…

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marks737

[marks737]

Thanks. I change oil prior to layup at the end of the season and usually average about 60-75 hrs a season. Just wasn’t sure if the oil was supposed to be black and if that meant it had degraded or not.

[John]

As long as you changed it already, you’re fine. It will always be black. It’s ok to drain a gallon (i.e. you won’t hurt anything) but I’m not sure most would bother swapping out 1 gal. to keep fresh. Either it needs an oil change due to hours or time or it doesn’t.

If you’re unsure of history and you just changed for first time yourself, maybe shorten the interval to the second change and change sooner, but after that follow normal service (hours / time) interval for oil changes.

Good luck

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marks737

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