Yes, another oil-related thread. I'm running 15W-30 Rotella dino right now and I'm at 3,000 miles on this change. With a good filter (this is not a filter thread). I grew up a few decades ago when 3,000 mile intervals were the norm and that's what I've continued with dino oil. I go 5,000 miles with full-syn. What do you guys think? Not just the obsessed among us who always take the most conservative choice with our trucks, but particularly those with some technical expertise to offer. Is it okay to run the dino 4,000 miles with today's better filters? 5,000? No extreme duty here, just a combo of city and highway miles.

 

You really can't use a certain mile as a true guide to change oil,, all miles & all engines are not equal,, also length of time between oil changes is also a factor,,,
Lets forget about the type & brand of oil & (lets assume we are using best oil possible, so we can concentrate on other factors),,
First it has a lot to do with how tight piston rings & valve guides are, the better shape they are in, the less contamination will find its way into engine oil, so that itself will allow oil to keep its original properties for longer,,, (a worn engine needs shorter oil change intervals),,
After that, the most important thing is driving habits,,, an engine that is being driven in short distances, pollutes its oil a lot more (sometimes 3-4 times more) than an engine that after start goes a long distance,,, why,? Because every engine produces water in combustion chamber when it runs, (roughly about a gallon of water for each gallon of gas it burns,) & you can see it very clearly at cold weather when starting any engine, (steam from tailpipe),, some of that water (steam) passes the piston rings and gets inside engine ,, today's good engine oils are designed to hold the water with in themselves so it doesn't hurt metal parts, and when engine oil gets to its optimal operating temp which is between 225*f to 235*f, water evaporates slowly and goes away,,, also when engine coolant is at optimal operating temp, (between 175* to 195*f), piston rings have tighter seal to cylinder walls, allowing minimal blowby, so less pollutants including water (steam) goes inside,, when any given engine runs in short distance, & gets turned off it doesn't give the water that is mixed with oil enough time to boil off & evaporate, so some stays in oil, & when this cycle repeted over & over, oil becomes more & more contaminated with water & oil looses its properties,,,,,
Another factor is how many millions of engine RPM for a give distance, it's very obvious that a car traveling in a fwy on last gear for lets say 10 miles, will do much less than a fifth of RPM's of the same car being driven in a stop & go traffic for same 10 miles, so it will polute its oil 1/5th for same miles,,,,
Another important factor is how hot the oil gets,, most oils Thermal breakdown temp is around 250 to 260*f, around those temps they start breaking down, (it changes their molecular structure,) so how cool (right temp) an engine oil runs is also a big factor,, when an oil breaks down it actually becomes thicker not thinner,! So it looses its quality to flow,,
,,,,, time between changes is also big factor, because when oil becomes acidic with contaminants it also starts loosing its original chemistry as time passes even if the car sits without movement , so if everything same we can use an oil for more miles if driven in a shorter time frame,,,,
So really a given miles per oil change can not be set for every application,, sometimes an oil can loose its qualities in very short miles, sometimes it can keep its original chemistry for longer miles, depending how it was put to work,,,
I would say an engine driven in fwy for 5000 miles will have a much better oil compared to same one driven in stop & go traffic with short trips for 2500 miles,,,
But when comparing the cost of an oil/filter change with in lets say 3000 miles to cost of the gas we used in that period of miles,, there will be no cheaper or better maintenance than changing it sooner than later to save money in long run, saving a few dollars to run the oil longer will not really save a disco owner anything compare to the damage it might cause in long run,,,,,,, (the damn thing's burns so much gas,!! That long oil change intervals is the very last thing that will save us any money on a Disco),,,
(3000 miles or 1-year is when I change oil on mine, whichever comes first, & that's with synthetic),, but everyone is free to do it their way,,,

 

It really all comes down to personal preference. If you have your used oil tested, you'll see that you are changing your oil (both dino and synth) at probly around half of their lifetimes. Chemically, it seems like most dinos can run out 5-6k miles, and synths 7-15k (wide variance due to different qualities of oils and different vehicles). However, as posted above, the unique issues with your particular truck and driving style can significantly shorten the oil's lifetime.

So, the scientific way to answer your question is pay the $25 and have a couple of oil changes analyzed until you nail down how long you can run a particular oil in your particular truck.

However, common thought here is that cleaner is better, so folks (including me) change their oil earlier than science supports. As I recall, I had some Mobil 1 TDT 5w-40 from my Disco tested after about 6500 miles, and Blackstone suggested I run it for twice as long next time. But I don't drive that many miles and basically change it once a year.

 

I can't make it past 3500 max on the Rotella 15-40. sometimes even 3K is pushing it.

 

What are the indications you see?
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I actually use a combination of Lucas stabilizer and the Rotella, except the 1-2 changes I did over the winter with straight Rotella. When fresh, the engine sounds and feels super-smooth. After a period of time, it sounds different on cold starts and when driving before it is completely up to operating temp. Not to mention the color change, but really I go by the sound of the motor.

 

I had the same issue with Rotella T. Right off the bat it sounded worse than the dirty M1 I had just drained, and then sounded worse and worse until I couldn't stand it anymore and drained it around 3000 miles. I do not have that problem with T6 or M1 TDT, which I run for 6-7k before I change, and it never sounds as bad as clean Rotella T.

Lately I'm been adding engine prolong, and I can't believe how quiet and smooth it is.

 

FYI, looks like new name will be T4.Shell ROTELLA® T4 Triple Protection | Shell

No personal experience with the dino Rotella.
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Interesting. I wonder if they are actually changing the formula or just renaming it to match the rest of the line.

 

I met an older local gentleman who has owned and services LRs since he could drive. He is of the opinion that even 10-40wt oil is a little light for the Rover V8 and suggested using 50wt and a stiffener made by Bardahls. It's mostly to benefit the oil pump gears and function; his adamant that this is the Achilles' Heel. I have been to his place and he owns no less than 3 Discos, and another half-dozen that he is servicing at any time so I'm so nieve as to not trust his word/suggestions/opinions or take them seriously. I have yet to use Bardahl brand, but I have found that an addition of a thickener is definitely beneficial if not entirely necessary.

This engine makes a lot of noise. I have used only the Rotella and Lucas since I bought it so my experience is limited to this, although the difference between the engine operation on fresh fluids and then after they are beginning to break down is easily noticed.