I have a 2004 Trailblazer. My daughter called and said the oil pressure dropped to nothing and it died and wouldn't start. My husband checked it and said she had hit something hard enough to rip the oil pan and it had probably dumped all the oil at that moment. Then she said she did hit something but not that hard and supposedly drove approximately 40 miles before it stopped. Would it go that far without oil?
Yes, it could go that far ... it really depends on the condition of the oil and the engine when the oil dropped, but yes it absolutely could go that far.
As a side note ... If she was able to get it 40 miles, that engine is completely toast and will require at a minimum, a complete rebuild. The easier bet here would be to just get a replacement engine from a reputable junk yard. A complete rebuild would cost too much for reconditioning parts. A new engine would be even more expensive.
Yes, that is possible, the residual oil in and around bearings can allow the engine to continue to run, but doing so is severely damaging the bearings and reducing the life.
One of the purposes of the oil is to remove heat so that is why the sump has such a large capacity.
I can confirm that an engine can go for a while after losing oil pressure. Years ago I had a Toyota Corolla that had one of its piston rods break and poked a 5" hole out the side of the engine block. Being I was on the freeway (southern CA) I was reluctant to abandon the car so I took an emergency U turn across the center median and headed back home. To keep the engine running I had to rev it up to max to smooth out the incredible shaking and vibration. Turned out I made it about 25 miles and the engine seized and stopped dead just as I started to turn into my driveway.
A 1973 Corolla was a very easy car to work on and I ended up getting a replacement engine from a junk yard for about $225 and changed it out myself in my garage. Took me about a day and after that I continued to drive that car for another two years until I could afford to purchase a brand new 1983 Toyota Celica.
The critical bearings in your car are plain bearings, because it's super hard to push a roller bearing over a crank eccentric. (Might be possible with camshafts).
Plain bearings are amazing, amazing things. They are nothing more than a polished, hardened steel surface spinning over a soft babbitt bearing material of matching shape.
For instance, railroad cars used plain bearings from 1825 up until about 20 years ago. Polished axle, babbitt bearing which shapes itself to match, under pressure. "Waste", essentially the stuff a mop is made of, wicks oil from a sump up to the bottom half of the bearing. The oil would stick to the bottom of the steel, be carried around to the babbitt, and then the entire railroad car would float on this cushion of oil. 7-20 tons on that axle (depending on dynamic forces in that instant) and it all worked and the industrial revolution was built on it.
In an automobile, because of the high revving and load and difficulty of maintaining a wick system, the oil is delivered under pressure to the bearing surfaces. The cushion is thicker, which helps durability, and doesn't require the bearing surface to shape itself to the steel (i.e. Normal manufacturing tolerances suffice).
First, the indication of an oil pressure light does not necessarily mean oil flow is entirely stopped. Oil is still being refreshed to the bearings, but it's no longer able to float the bearings with the large cushion, so the bearing is reverting a bit to "railroad style" and shaping itself to the steel. An engine could continue for quite some time with too-low pressure but still, oil is being refreshed, so the damage is being contained.
However, if oil pressure is removed entirely, as with a hole in the bottom of an oil pan, then the oil still at the bearing stays there, because it wants to. Now it's acting like a railroad bearing, but without being replenished by the waste. This will work for an indeterminate amount of time.
Eventually, the oil will just cease to be sufficient, and now you have a "hot bearing", and that degrades very quickly to destruction.
I had the engine in a VW Bug seize up, due to lost oil. I added oil and the engine freed up as it cooled. After that, it started and I ran it for a couple more years.
Course, that was back in a day when tolerances were lax, and pistons clattered around in the cylinders, relying on the rings to maintain compression. I concur that a modern engine is far less likely to survive such an event...
Unlikely but certainly possible.
If there was no oil at all getting pumped it would seem surprising.
But if there was a small proportion of the oil left but the pump was able to recirculate it in occasional spurts then it could happen.
To assess likelihood you'd need a fairly complex look at how much oil MAY have been left, where it sat relative to the pump input, how likely it was that the pump could pump what was there , ... .