I got a 2000 Ford Windstar 3.8 I built a building up north and in my obsession with that I hauled an incredibly large load of lumber with the van low on oil.
When I finaly found out.....weeks later?, I was 3 - 4 quarts down! I always figured I broke a piston ring....
The van uses a LOT of oil in city driving now, and less on the road. It was developing very rough "fluttering" shaking at start up of acceleration. I got 120,000 on it now and the shaking was getting bad... I had plugs and wires put in new by at home mechanic.
Runs better .....start up shudder is gone pretty much, but now at idle coming to a stop it studders and gets worse as we sit. I sat for a while the other day....and it shuddered and the oil indicator light even came on. A quick rev eliminated that. For a stop light we might put it in neutral.
There is some clickking noise in the engine at time early in start up, but no big knocking. NOW TODAY, starting this morning....when we start it, many of the starts include a big blue cloud on start up.
I got to get some more miles out of this.... $$ real bad for us right now. Been limping along with the problem from the original miss use last year. Few quarts every week or so in the city, and not that much over the road.
Now it is getting worse of course.... I'm guessing I should use the motor honey thickener to buy me more time... Any certain brand? Any other ideas?

 

blue smoke or white smoke?

 

Sounds like you may have damaged bearings as well when you ran low on oil, and this is why you have low oil pressure.

 

check also the head gasket, it could be the problem.