On my 96 Disco SE the oil light comes on after about an hour of driving. It only happens while I am stopped at idle speed in gear. If I shift to park and the idle comes up slightly or if I accelerate the light goes off. I checked the oil level and it is not low. Yes the truck has high miles, 203k Any thoughts? Spike, Mike ?

 

put a gauge on the motor and check oil pressure, 2 options i can think of, mains and big ends getting down, oil pump worn, cam bearings possibly, if it uses no oil and makes no noises you can do the mains and big ends in place.
you will have to plastigauge the bearins to make sure the crank is not worn, earlier you get on to it the cheaper it will be.



Cheers

 

I had an oil light issue - similar to your issue -
I had heard that the oil pressure/send unit was known to fail - so I spent $20 for a new sender - Installed it and the problem still existed -
I contacted the PO and he stated that when he got the oil done, they put in 5w30. I read here that this could cause the problem I (and maybe you) was having. I put in Royal Purple 15w40 - and the oil pressure light hasn't come on since.

Seems that the Disco V8 requires a thicker oil then "standard" car engines -

In Peace and Agape,
Trav..

 

What oil are you using?
5w-30 is way to thin for these things, especially in the summer you need to use at the very minimum 10w-40, 15w-40 is best for the summer and 5w-40 for the winter where you live.

 

I was having a similar problem. I think I was using 5w-30 or 10w-30 mobil 1. When the truck was on all day during an offroad trip or I would drive for more than an hour on a really hot day, the oil light would flicker or come on when idleing. I switched to Rotella 15w-40 and have not had a problem since, about a year now.

 

Since the oil switch operates when pressure drops to between 3 and 6 PSI, and 2500 rpm should bring 40 PSI, light on at any rpm when running is not good.

 

First, he needs to stop driving that Disco and have the oil pressure tested, cold at idle and at 2000 RPM's and warm at idle and 2000 RPMs.
Most likely the pump has failed and there is a possibility of bearing damage at that point.
For all you 5 and 10W/30, quit using it except in the middle of winter at 20 below, stay with a 10W/40 or higher oil so you can protect your engine.

 

I had the exact same issue, pressure was fine - switched to 10w40 - GONE!