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rws
10-22-2017, 06:06 PM
I respect the opinions of the folks here. I have a Dodge Cummins diesel with 102K miles. Since new, I have used Rotella T 15/40. Since obviously it doesn't get driven that much, I was thinking going synthetic. I have used nothing but Mobil 1 in my Chevy gas truck, with no issues. Any opinions?

flylo
10-22-2017, 07:06 PM
I have one of the last 12 valve 5.9 Cummins in the flatbed & have 115K. I've always used Rotella T 15/40. Both mineral & synthetic has good points so I'd like to find & use a semi synthetic, best of both worlds when engines sit. Here's an aircraft oil that works well when planes sit alot http://www.brownaircraft.com/product-p/shell15w50.htm.

nickel-city-fab
10-22-2017, 07:30 PM
That Rotella T oil is good stuff, I use it in everything just for the detergent package. Even in the lawnmower. I think they make a full synthetic version called T6.

My experience is that the synthetic stuff doesn't break down as fast -- it keeps its viscosity about 2x as long even when its completely black. Its also a lot easier starting when cold, we had a month-long run of -20F days here a few yrs back and yes the synthetics did a lot better in that weather.

Only drawback is that the good stuff ain't cheap.

Michael Edwards
10-22-2017, 07:51 PM
I think they make a full synthetic version called T6.

Only drawback is that the good stuff ain't cheap.

I use Rotella T6 in my sport bike. It's every bit as good as the $15/ liter eni oil I was using, but it is only $21.36 a gallon delivered to my door from Amazon. To me, that's pretty reasonable for a top tier oil.

tom_d
10-22-2017, 08:34 PM
The synthetic oil would be a great choice if you were in a much colder climate, with sub-zero temperatures throughout a long winter. Otherwise, you can't do much better than your current oil. If you are concerned about problems stemming from the engine sitting for extended periods of time then maybe shorten the drain intervals so the engine sits with the freshest oil possible.

A.K. Boomer
10-22-2017, 09:10 PM
Willy's the man to talk to on this and im sure once he see's "oil" in the OP he will chime in,

here's my two cents for what it's worth,,, synthetics are superior protection, whilst the engine is running that is, it's actually not very good when engines sit for long periods of time and have to deal with humidity/oxidation,,,
for that conventionals rule the roost, so actually what flylo suggest might not be a bad compromise and yeah Rotella has got the covered too...

vpt
10-23-2017, 07:33 AM
Heres the trick.

Motors don't break down from bad oil.

As long as you change it when its time it doesn't matter what you use the motor will outlast the vehicle.

We run all our trucks till 500K miles and then retire them. The diesels ran on Rotella, the gassers ran on all kinds of stuff. Never an oil related problem.

MattiJ
10-23-2017, 08:08 AM
Heres the trick.

Motors don't break down from bad oil.

As long as you change it when its time it doesn't matter what you use the motor will outlast the vehicle.


I'd say that well engineered motor won't break down from "bad" oil. But plenty of badly engineered engines out there:
VW pumpeduse camshafts
Saab 2.0 and 2.3 Turbo engines around year 2000 with oil sludge
Half of the Citroens and Peugeots puking oil at winter.


BTW: intresting to see how the new Ford Transit diesels are doing with the 50 000km or 31 000 miles! oil exchance interval.

Doozer
10-23-2017, 08:30 AM
Why should it be obvious to us that it doesn't get driven that much?

-D

rws
10-23-2017, 11:31 AM
Why should it be obvious to us that it doesn't get driven that much?

-D

8K per year aint much.

Willy
10-23-2017, 12:53 PM
Synthetic oils are undeniably a better lubricant than conventional oil for various reasons which are well documented elsewhere. The qualifications of full synthetic lubricants go well beyond the scope of a simple answer to the question of should I switch.

One has to factor in the cost effectiveness and viability of the decision. The Cummins engine in your truck can easily achieve 500,000 miles before any major internal work is required, this with conventional oil. I know of two individuals that use their trucks in commercial highway delivery service that are coming close to the one million mile mark using conventional engine oil. These trucks operate under ideal conditions and are serviced regularly, but it does demonstrate clearly that the type of operation conditions the truck operates under are more important than the type of oil used.
At 8,000 miles annually it's going to take over 62 years to accumulate that kind of mileage! Will you still be driving that truck in another 50 years? I've got an older 12 valve Cummins as well and this is what I asked myself as well when contemplating a switch to synthetic oil.

Unless the engine sees severe service like short trips where the oil does not come up to temperature the engine will easily outlast both you and the truck. In cases where the engines does not come up to operational temps routinely, more frequent oil changes are required, so throwing out expensive oil is not a cost effective answer here either.

In many cases going to a full synthetic is more of a "feel-good" choice than an actual rational decision.

vpt
10-23-2017, 06:10 PM
I'd say that well engineered motor won't break down from "bad" oil. But plenty of badly engineered engines out there:
VW pumpeduse camshafts
Saab 2.0 and 2.3 Turbo engines around year 2000 with oil sludge
Half of the Citroens and Peugeots puking oil at winter.


BTW: intresting to see how the new Ford Transit diesels are doing with the 50 000km or 31 000 miles! oil exchance interval.


A persons got to expect troubles with those types of vehicles no matter what they do. :D

adatesman
10-23-2017, 07:00 PM
8K per year aint much.

While you gave the mileage in the OP, you neglected to give a year.

Tim Aldrich
10-23-2017, 09:19 PM
I work on big trucks. Some of our long time customers have put 1,000,000 on their engines with plain 'ol petroleum 15w40. Change the oil and filter regularly, use decent parts and you'll be fine. As long as you're on top of the maintenance, the truck will probably rot out from under the engine before the engine fails.

michigan doug
10-23-2017, 09:41 PM
A persons got to expect troubles with those types of vehicles no matter what they do. :D

It's a testament to how good cars and engines are that we would look at 100,000 miles as poorly engineered.

Even the risky ones, my 2004 VW pump deuse turbodiesel tdi is getting very close to a quarter of a million miles. Doesn't burn oil, starts right up. Routinely give 46 mpg and I tow a trailer with 1,000 pounds or a little more at least once a month. No complaints from me. 10,000 mile oil changes. VW did spec a very very specific oil and there was a warning in the owner's manual that if you used anything else, you could have catastrophic engine failure and die.

I had to tune up the parts guy at the VW dealership more than once when they tried to sell me the wrong oil.

danlb
10-23-2017, 11:28 PM
Several posts speak to the extreme longevity, but fail to note that the OP is not driving much any more. It seems the formula for getting a long life from a diesel is to drive it regularly and service it regularly.

When you start to drive infrequently the "every 10,000 miles" service becomes every year or two, and that's not always good for the oil due to detergent breakdown based on age.

I don't drive a diesel, but I am not driving my car as much as I used to. A single service change once a year works fine with synthetic in my circumstances.

Dan

dave_r
10-24-2017, 01:21 AM
Pretty much all vehicles stay in good working condition longer if they are used regularly. Doesn't have to be lots, just regularly, so all the various oils get sloshed around on everything inside, seals get lubed and don't dry out, battery gets charged up, stuff like that.

And I know GM (at least for my truck) has a DIC which notifies my when to change oil, but also writes in their owners manual that if you don't drive much (so the DIC doesn't notify you), you should change your oil annually.

vpt
10-24-2017, 07:02 AM
My 7.3 diesel excursion only gets used for pulling trailers and camping in summer. Usual summer I may only put 2000 miles on it. This year I put on around 5K because we took it to Maine. I change oil on it once a year in spring. 15-40 dead dinosaurs always.