Your mechanical questions, answered!

Qualified mechanic Adam Adler has spent half his life under the bonnet of a 4WD and has worked for some of the top accessory companies and workshops. He knows what it takes to get your vehicle out there and back home in one piece. He runs the online aftermarket store


Hey Adam,

I have fitted a catch can to my 4WD. I drain it every 5000kms but have been thinking that if it was plumbed back into the engine sump it would self-drain. Is there a reason why I couldn’t drain it back into the sump?

Thank you,

Keith Hildebrand, Orange, NSW


Hi Keith,

The catch can really is an oil separator and probably should be called that, not a catch can.

It’s quite common to not only see oil in the drain of the catch can but also water and moisture, depending on the climates and use of the 4WD. Personally I would continue to drain it and dispose of the waste.

I don’t think it’s a good idea to drain it back into the engine sump.



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