Yes, the diesel oil has extra cleaning stuff, and properties to control soot in a diesel, which keep particles in suspension so the filter can trap them. So it does a better job of cleaning the engine. Diesels have a much higher compression than a gas engine, and demand a tougher oil.

Now as to your truck, we know that oil PSI dropped below 7 PSI while operating at high rpm. That turned on the light. Twice. The light turns off at 8 PSI or so. The normal 2500 rpm PSI should be 40. You don't know if your's is 12, 20, 31, 44, etc. Even after the oil flush ritual. So if you can spring for an oil PSI test, it won't hurt the truck.

 

The oil light also comes on where there is no oil in the oil pan for it to suck up and pump through the engine.
The only reasons for the oil light to come on at highway speeds are a catastrophic failure or lack of oil.
If the oil pump were bad or bearings to worn the oil light would come on/flicker at a hot idle.

 

If you are taking the pan off, you are very close where a manual gauge could be easily attached. If paying a shop, it won't be too much more labor.

The engine has two places where a couple of quarts of oil can sit, the oil pan (desired) and the valve covers. The sludged up passages in the heads to engine block to oil pan don't allow the oil to flow back quickly enough, as you mentioned, and oil starvation results, because not enough in the pan to slurp up.

A quick flush may help, but poking a rod or stiff wire down some of those vertical passages helps also (valve covers off). The oil is under pressure through the bearings and the rockers, but plain old gravity drain back to the pan. So it does not take much sludge to slow it down.

This is a good reason to run a jumbo oil filter, the extra capacity of the system reduces the times this sort of "drain back up" will occur and leave engine without oil. Including odd extreme angles on the trail.

 

So, I should be using diesel oil 15/40 in my 95? I have been running Maxlife. Where do you get the jumbo filter? I had my oil pan gasket replaced, but the shop didn't say anything about a filter....

 

Maxlife 10w-40 would be a suitable oil, it has extra cleaners and stuff in it but diesel oil is better and cheaper.
$12 for a gallon at Wal-Mart.
Dont worry about the jumbo oil filter, just dont use Fram unless it is the Extended Guard, that is a good one but still costs more than one from NAPA which is a better filter.
Use the NAPA middle if the road oil filter or a Purolator, the PureOne filter is rated as the best you can buy, but it is expensive and a waste of money unless you are doing 10,000+ mile oil changes.

I use Shell Rotella and NAPA oil filters and change my oil every 5,000 miles.

 

When at the store look at the Purolator L40316, like Spike says it is a good brand.

 

That Purolator L40316is actually manufactured by Mann which sell huge massive special purpose rigs primarily in Europe and they relabel it as a Purolator, it is oversize and cost like 6 bucks at Pep Boys and has an built on nut to install it and remove it with a wrench, which I really like. Best filter for the money.

I would second the motoion to remove valve covers for a visual and the sump for a visual, why risk a motor?

They also sludge up from years of running cheap gas. You could get a peek just by removing your oil filler cap and see the corner of the inside of the motor.

How many miles on it? Doing your own oil changes helps you begin to learn more about your Rover and you save a lot and do it right yoursekf better than the minimum wage idiots at a fast change place. It takes about 7 quarts of oil so get at leat two of the jugs of Rotella at Walmarts aand you might even see some trashy women while you're there, take pics of them if you do!

Buy three jugs of Rotella and you will have enough for two oil changes! You can get one of the change kits that has a catch basin, take your old oil in and they accept it for recycling or do what Spike does, change it over the drain at the 24 hour car wash stall at 2 am!~

 

Following Spike's diagnosis, if it is thick sludge causing slow drain back, engine flush might get all of it, or just some of it. We don't have x-ray vision and can't see how low the oil pool in the pan is getting at sustained 70 mph. Mechanical rod out (just a stiff wire or get fancy with a gun barrel cleaning brush) will give whatever combination of high cleaning oil and engine flush system an easier job of it. The big Purolator filter adds some capacity to the oil system, which will also help the issue of slow drain back. If under the valve covers look like this, could be an issue. Basically you can poke a wire down any hole found in the head that does not have a bolt or push rod in it. Note that each rocker tower has an oil port that pressurizes it and feeds part of the valve train. But the oil drains back by gravity thru just two ports I believe.

 

A larger oil filter will do nothing to help his problem.
Yes it will hold more dirt, but do you need to hold more dirt? Are you going 15,000+ miles between oil changes?
Lets not confuse "holding more dirt" with "filtering more dirt", they are two entirely different things.

 

Sorry to have an alternate opinion, but the jumbo oil filter holds more oil that is between the pickup and the point of the drain back restriction. The "blocked drain" continues to drain at the same slow rate, but there is additional oil to increase the time it takes the oil supply to be exhausted. I agree that filter media has nothing extra to do with this. Likewise, a custom oil pan that added another quart of capacity would do the same thing. I actually think that Spike has made a good case for using the large filter, just in case you start to get sludged up and don't know it.