Last week I was stuck in peak hour traffic on a highway when my oil light came on.. then went off.. then came on.. and did that a few times until it stayed on. I couldn't get out of the jam, there was nowhere to move and I had to sit there for several minutes until the traffic started moving, but by then the light had gone off again and had stayed off for a bit.

I figured by that point damage had already been done, and the light was now off so I may aswell drive it home. On the way I noticed that the oil light came back on if the car dropped to 40km/hr or below, and disappeared off above that speed.

Temp gauge wasn't moving, couldn't hear a rattle or change in the engine sound, by now catastrophic damage was supposed to have occurred but it hadn't. My drive home was at 100km/hr and at that speed the light wasn't coming on so I thought perhaps it was just the pressure switch that had failed.

When I got home I did an oil change, changed the filter and put a new oil pressure switch in it but the oil pressure light was on when I started the car. So I turned it off and had it towed to a mechanic, figuring now that I've dumped the old oil and the pumps in this model don't self-prime, I'm not game to turn it back on. Basic maintenance is the extent of my skillset but changing oil pumps is not.

The mechanic said it had no oil pressure - which I already knew - but then said he can't work on it until next year.

I had it towed back to my house today as I've found another mechanic who has time to look at it in a few days, but the engine bay now has a cooked engine smell to it.

When I dumped the oil I couldn't see shavings in the pan or filter, but admittedly I've never seen them in person so I'm not sure what they would look like.

It's a 3.2L 2012 ford ranger diesel with 260'000km on the clock. This model uses a variable flow oil pump which is apparently prone to spontaneous failure. I wish I'd known beforehand.

The new mechanic is going to put an old-style fixed flow oil pump in it but I guess I'm wondering what my chances are of the engine being too far gone? 

I have surgery in a few weeks and this is my only form of transport in a new town where I know noone, so I really need it patched up for now. If it does need a rebuild, can it be driven with the new pump until that time or will doing so continue to damage the engine?

Any input would be appreciated, thankyou.

What are the chances of needing a new engine/rebuild after loss of oil pressure?