As regards the comment that there’s no oil in your driveway therefore it cannot be leaking, that is a common erroneous assumption. First of all, there are paths for oil to leak that only become active when the engine is running, such as the rubber seals for the ends of the crankshaft. These typically only leak when the shaft inside them is spinning, and the crank seals only when there’s pressure from the crankcase, normal in an operating engine due to normal blowby and expansion of the fluid due to turbulence when operating, both normal conditions. Crankcase pressure is such a normal part of an engine operation that all engines have a Positive Crankcase Ventilation (PCV) system to allow the pressure from the crankcase to be relieved in a manner that won’t allow unwanted hydrocarbon vapors to escape into the atmosphere.
The true cause is probably going to end up being too long a time period between checking the oil level combined with some form of slow leakage. Most manufacturers consider a quart of oil usage every 1000 miles to be acceptable even on a new engine, some allow even more. In 3,000 miles that means you could have used 3 quarts of oil, leaving one quart left. When you start the engine, enough of that oil goes up onto the engine to allow the level in the oil pan to drop below the oil pump’s “pickup tube”, which draws the oil from about 1/4" to 3/8" above the pan’s bottom.
The way the system works is that the oil “pan” is just that, a metal pan from which the oil pump draws oil. The pump does so through a “pickup tube”, which is just a metal straw with a larger surface area flat disc with a screen on the end to reduce the chance of getting plugged by gump. The pump then forces the oil through the engine and into the spaces between the wear surfaces. The oil then just drips back into the pan. If the oil drops below the straw, the oil pump draws air and the oil pressure disappears, triggering the warning light.
IMHO, and with no disrespect intended, I think the negligence is 100% yours. You need to learn to regularly check your oil level and keep it above the “FILL” line.
Some will argue that a quart every 1000 miles is excessive, but that’s a totally academic argument that we engage in occasionally about exactly what’s normal. The bottom line here is that you don’t check your oil.
On the “good” side, you took it in immediately when the light illuminated. You may have saved your engine from total destruction. I’d recommend that you have them do a complete oil change (in case there’s a minor leak in the filter gasket or the pan plug), monitor your oil from there, and hope no damage has ensued. If it has, IMHO you’ll just have to assess the value of getting it fixed and, if you do, consider the cost as tuition in the school of proper maintenance.
