If the oil was that low after just checking it then someone is not looking well enough either for the leak or if it is burning it. Run your finger in the inside of the tailpipe and then look and smell your finger for oil. If it is there, it is burning it, but that does not also mean there is not a leak. Check all around, up and down, side to side of that engine for a leak.
Running the oil that low can be dangerous bit if the oil light never came on then you may have gotten lucky and not damaged anything.
I would not run it for five hundred miles then bring it back to them. Check the oil level constantly, at first every day, then afterward at least every other day and as soon as you lose one pint, take it back.
Monday, February 12th, 2018 AT 7:16 AM