I have a 2006 hummer3, was wondering if there is a light that goes on if you need oil
Most likely no. The only thing that I'm aware of that would indicate a problem would be the oil pressure sending unit. It would throw a code and activate the "CEL" if there is low oil pressure, which would indicate a low oil level condition or oil pump failure. My recommendation would be to check the oil level on the dip stick as part of a monthly service routine and never let it get to that point.
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