Dripping Oil Can Warning Icon: What's Most likely Cause, Please ?

Oil is low or the [pressure sensor thinks the] oil pump's pressure is too low. Turned out for me, when the oil icon appeared, that the pressure sensor was bad.

When you checked the oil level, had the car been sitting for a long time, or did you check right after driving and turning off the engine? When you check the dipstick, did you remove, wipe, put back in for a few seconds, remove, and recheck the oil level? I usually check with the engine cold and warm to get an idea of how the level fluctuates.

A dirty oil filter would block the oil flow. Some oil changes don't include an oil filter. Check with the shop if they include an oil filter in their standard oil change. Where was the oil change done? At a car shop or some flunky quickie lube joint?

Did he ever put the stuff that gunks up in the oil to seal leaks?

A car shop should know if they put in a new oil filter, and they can check. They can also measure the oil pressure to know if the pump or sensor are bad. Since they'll be removing the sending unit (sensor) to attache their oil pressure guage, might as well ask if they'll have a replacement sending unit on hand, so you don't get charged twice for removing and inserting the sending unit.

Yeah, you could do it yourself. For the cost of buying an oil pressure gauge, I found it only a few bucks more to have the car shop do the work. The sending unit is cheap, like about $10 to $20 for your son's car, so you might as well have one on hand when the shop does the pressure testing. If they don't find a problem with the sending unit, take it back for a refund; else, they've already done the work, and if they find the sending unit is bad then they'll have another to put in without you having to come back to redo all the work or having to leave your car there all day until their runner gets a replacement.

When I see the oil light, I'm far more concerned than, say, if I get a check engine code that points at the evaporator system. Lack of oil is lethal. Some fuel vapor leaking out isn't. I've been seeing the code for an evaporator leak for months and will get to it when I've got some spare cash. When I saw the oil light, I got an appointment as soon as possible.

Don't know what is you or your son's budget. To have the shop check the pressure and put in a new sensor was not much more than me getting an oil pressure gauge and buying a new sending unit. Depends on the rapport you have with the car shop and their reputation. If you used a quick-lube joint, don't go back there to have them fix the problem (as they won't since they just replace lube). I've found my local shop to be no more expensive for oil changes than the quickie-lube joint, and they often send out flyers or have online coupons for discounts.