I have a 2002 discovery that I recently purchased for a good price- it has 133k miles on it- today I was about 2 hours away from home and the oil light came on and the truck started making a ticking / tapping noise - I was doing 75mph and was in heavy traffic and slowed down to 55 and pulled off to a gas station- the light was only on for about 20 seconds and the light shut off once I got down to about 55- the noise went away as well. I checked my oil and it was a liitle over full actually but looked clean and fine -
Any ideas what happened? After I got home I am now noticing a oil smell from the engine -
Not sure if it means anything or not but I have noticed that there is a black grime around the tip of my exhaust pipe as well-
I'm a newbie and not too knowledgeable on the rovers yet- any thought are appreciated!!! Thanks!!!

 

Did you notice if the temperature gauge was rising into the red when your were driving at 75?

 

I think you are going to low your engine of you keep on driving it. Get it towed to a shop and get your oil pressure measured. You probably need to change out the oil pump gear.

 

was the truck misfiring at all? Seen alot of people think the oil light is the problem but the vehicle misfires so badly the rpms drop and the oil light comes on briefly.

 

Engine sludge, the oil cannot return to the oil pan fast enough to supply a adequate amount of oil to the engine.
The oil pumps from the bottom up and then drains back to the oil pan and starts all over again.
If it is all inside the valve covers there will in effect be no oil in the crank case thus the oil light coming on.
Slow down and the rpms drop and the demand for oil slows and then it can drain back into the sump fast enough to supply the oil pump.
The burning smell is the oil leaking out of the valve covers, they are not meant to actually hold oil, just retain it.
Its like a water proof watch and a water resistant watch, you can take one into the hot tub but only wash your hands with the other.
After you stopped and shut the engine off enough oil had drained back into the oil pan to give you a good reading on the dip stick.

You have several options.
Change the oil and use a high detergent oil like diesel oil or full synthetic.
Go get a professional engine flush.
Try and clean the sludge yourself with a off the shelf engine flush.