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first oil change, synthetic or standard

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I use 15W-40 T4 in my coach, I use 5W-40 T6 in my diesel powered personal vehicles that sit outside in Minnesota winters and need to start! Just my opinion. 
 I used T4 in my Peterbilt’s for over 2 million miles.

 I agree with Robert U ‘s opinion on the Synthetic oil use!

Edited by Jdw12345
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I have another opinion. I run synthetic in my coach because I like the stability of the viscosity of the oil through many many temperature cycles. I do the same thing with the generator and as most people do here I run synthetic in the transmission for all of the same reason.

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1 hour ago, Knight 40 PLQ said:

First oil change for new to us Cummings 8.3 with 36,000.  Debating T6 or T4 Rotella with Baldwin filters, Did the transmission last year cost was about $250 and I did the work, any comments are appreciated.


Tractor Supply sells the Vavoline “Blue” which is the recommended or preferred lubricant bu Cummins.  I have run the Shell.  My late FIL, a farmer who maintained all his tractors and loaders, swore by the Shell.  BTW, he was moved from being a “line flight engineer” on several “B” series bombers during WWII, and then taught flight engineers as his planes had the most “up time” of his squadron…. So, l always respected his advice.

I do not see the need or value of a synthetic for our use….and many of the Cummins tech support personnel express the same opinion.

That’s my take and I averaged 6K per year for a 10 year period, so the rig did not sit ariund. I run the Vavoline in the Onan genny…

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If possible find out what oil has been used by the previous owners and then continue using that.  I run the Rotella T4 in all my diesel motors and swear by it as i change the oil on the proper intervals.  If you don't want to change the oil and just change the filter then run the synthetic...otherwise I agree with the others that synthetic is a waste of money.  

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14 hours ago, Tom Cherry said:

Tractor Supply sells the Vavoline “Blue” which is the recommended or preferred lubricant bu Cummins. 


I look for sales on Valvoline Blue, usually between Tractor Supply and Autozone I can accumulate enough oil for an oil change and keep enough on hand.  Tractor Supply recently had a sale on if for $12.99/gallon and I bought all they had on the shelf. 

I know this will get a lot of push back but I started changing my oil every 2 years BUT I do oil sampling and have had no issues, the results come back good.   When I was working we'd do oil changes every 200 hours (~2 weeks of run time) on equipment that was run hard but we did oil sampling.  The one thing I looked at on the reports were any signs of silica which was an indication of air filtering system issue. 

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Want to start a thread war?  Mention Rotella on a motorcycle forum! 

I use Rotella T4 (only comes in 15W40) in our Cummins ISC and dirt bike motorcycle transmission, and use Mobil 1 full synthetic in the 4-Runner and Mini Cooper (Euro formula) gas engines.  Not necessarily the BEST oils on the market but IMO in the upper 10%.  When combined with availability and cost they work for me. 

The way the Cummins reps described it (visited our 2022 gathering) diesel engines have a much greater tolerance between bearings than gas engines and didn't need the smaller molecules or consistency of synthetic oils.  Bottom line, they came up short of saying synthetic was a waste of oil in diesels.  They also mentioned 15,000 miles between changes wasn't a problem, but I don't recall a time limit . . . . yearly? 

That was Cummins reps.  Want to read waaayyyy more than you ever wanted to know?  https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/

- bob

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Decades ago I asked a big engine rebuilder which oil. He said Delo 400 were the cleanest followed by Rotella T4 having a slight buildup. Since I had engines that sat a fair amount went with T4… Sam’s $300 for a 55 gallon barrel.

Currently need to take a sample and see how much longer before changing… at 10,000 miles and 2 years. Last time I went to 15K (could have gone longer) but was leaving on a long trip. If you change every year, I’d like to recycle your oil.


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Years ago I had a coach with a CAT 3126 that exhibited a low oil pressure issue at idle after the engine had been run hard and was hot.  My diesel mechanic BIL recommended switching to synthetic oil to get a better viscosity profile when the oil was hot.  Years later I had an engine that exhibited a high oil pressure issue (over 100 psi) when the engine and oil were cold.  BIL again recommended synthetic oil because it flows better at low temperatures.  If you have either of these issues, then synthetic oil is probably worth the extra cost.  Otherwise standard 15W40 is probably fine.  Whichever you use, I strongly recommend you have the oil laboratory tested every year and keep the test results for future comparison.  I use Blackstone Labs for testing and follow their recommendations as to when I should change the oil, or of it has adequate additives and is clean enough to run longer.


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7 hours ago, Tdkkart said:

Any name brand off the shelf oil in the proper viscosity range will be fine. Oil companies are not in the business of making crappy products, they stand to lose MUCH more if the public starts having proven oil related failures.


There's more to oil than viscosity.
Your oil needs to be rated for compression ignition engines, which accumulate much more soot which the oil needs to keep in suspension.
Using gasoline rated oil can sludge up your engine quickly.

The only time I buy conventional oil is for first startup and break-in of freshly built engines, or when replacing a camshaft in a flat-tappet engine.

I run Rotella T6 in all my diesels. The 5-40 viscosity range gives good cold-start performance, and maintains a good oil film at all engine temperatures.

As far as my street gasoline vehicles, it's been Mobil-1 in whatever viscosity is appropriate for bearing clearances and temperatures.

Engines and transmissions are expensive, synthetic oil is cheap insurance.😉

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Opinions are like....well, you know the saying. If you want cold, hard facts, check out "Project Farm" on YouTube. This guy has tested all sorts of oils, pays for everything himself, and he isn't sponsored by anyone. His videos are the most objective I've seen.

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I'd put a good stiction cleaner in there with the new oil, I use the Secret Hotshots and their FR3 on the future oil changes W/O stiction cleaner.   I also use their Diesel Extreme every 6K miles in the fuel and I use their Everyday diesel on each fill up.  Many brands to choose from.  FWIW I run full synthetic Amsoil in the motor and Genny, I use to run the Rotella T5.  Congrats on the rig! 

Safe travels

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56 minutes ago, Les Hurdle said:

My garage mechanic keeps plugging Amsoil.......




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I am by no means a mechanic, however, growing up around heavy machinery, operating them, servicing them and listening to the experience that came before me has kept me out of unwanted trouble.

I have been told, if its a new machine, use either, but whatever you use when starting out, keep using it, don't change. If you have a used machine that has had non-synthetic oil and then suddenly you use synthetic,,, can cause some issues. One is that synthetic oil does clean the deposits and grime that has built up through time from regular diesel oil. The grime that has built up through time actually helps seal and eliminates leaking. With a sudden change to synthetic could create some leaking. I use  shell Rotella 15/40 diesel oil. I travel from Calgary, Alberta to Puerto Vallarta Mexico every year now for 10 years. I change my own oil and all filters fuel/oil every year at the same time in Mexico. I probably could get more miles but I would rather know my engine is running on clean oil and fuel. Round trip is about 5500 miles.

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From Shell Oil.  FYI.


Synthetic oil allows all parts of your engine to work together and protect it from damage and failure. There are several preconceived notions about engine oil that are not correct, Shell Rotella is here to help you separate fact from fiction.

1. You can’t switch back to mineral oil after using a synthetic oil

Switching back to conventional oil from synthetic is absolutely safe. You can change from the 5W-40 synthetic oil you used in the winter to a 15W-40 conventional oil in the spring. We offer Shell Rotella T4 15W-40 conventional oil and Shell Rotella T6 15W-40 full synthetic if you want the added benefits of synthetic oil technology.

“During colder months, it's a good idea to switch to a lower viscosity oil – in this case, synthetic oil – to provide improvements in engine stability,” explains Karin Haumann, OEM Technical Manager for Shell Lubricants.

Haumann adds: “Because a synthetic oil can meet the same OEM specification as a conventional oil, the question is, are you willing to relinquish the inherent benefits a full synthetic product can give you?” With the proven benefits of synthetic, you can use it in your engine all the time.

2. Synthetic oil is too expensive

While synthetic blend and full synthetic oils may cost more upfront, the benefits they provide make them worth the investment. “The benefits Shell Rotella® synthetic motor oil provides in terms of engine protection, longer oil drain intervals, and equipment durability over the lifetime of the engine easily outweigh the cost,” said Haumann.

Shell Rotella® T6 Full Synthetic engine oils provide protection that can save money with enhanced fuel economy capability, without compromising engine protection or durability.

Key performance and fuel economy benefits of synthetic include:

  • Lower oil consumption to help reduce maintenance costs 
  • Increased protection against oxidation for increased fuel economy 
  • Excellent corrosion control to help protect key engine parts 
  • Low Ash formulation for emissions system compatibility

3. Only newer engines need synthetic oils

Synthetic engine oils are designed to provide improved protection for a range of extreme working conditions in new and older engines. Whether you’re stop-and-go driving or working in freezing cold or desert heat, synthetic engine oils are designed to:

  • Improved engine protection 
  • Promote engine cleanliness 
  • Keep operating temperatures cooler 
  • Lubricate the engine quickly when starting in cold weather

If your engine is designed for higher performance that will put higher stress on the engine and the oil. It’s best to have a synthetic oil that's better at withstanding that stress.

“It’s well known that synthetic products can protect engines better than conventional oils,” says Haumann. “Most new vehicles require a XW-40 or lower synthetic blend type oil because it improves startability in heavy-duty engines and offers real advantages in fuel economy.”    

4. You can't change brands of engine oil

As long as the specifications and approvals of the new oil meet what is required by your engine’s manufacturer, you can switch between brands with no issues. Though several brands of oil may meet the same industry and OEM specifications, they often have different performance levels.

Shell Rotella® offers a complete portfolio of synthetic and synthetic blend heavy duty engine oils that are suitable for virtually all modern low-emission heavy duty engines and older hard working diesel engines. With its wide range of specifications, and approvals from many of the world’s leading engine makers, the oils are an excellent choice for on-highway fleets, general haul, construction, agriculture, public-transport operators and diesel pick-up trucks.

Drain the oil and you can change brands. Shell Rotella meets or exceeds current CK-4 and other standards

5. High viscosity oil is best

With Shell Rotella T5 10W-30 synthetic blend, you get the strong wear protection of a 15W-40 with the added benefit of fuel savings.1

In addition, Shell Lubricants has introduced Shell Rotella® T6 10W-30 full synthetic heavy duty engine oil, which provides the benefits of a full synthetic engine oil in the fastest growing viscosity grade for diesel-powered vehicles. The versatile oil offers fuel economy benefits and excellent engine protection for hard working trucks.

Shell Rotella® T6 full synthetic engine oils provide protection that can save money with enhanced fuel economy capability, without compromising engine protection or durability. The oils also perform extremely well in heavy duty diesel engines even in extreme temperatures, meeting and exceeding industry performance standards.

Shell Rotella® T6 15W-40 Full Synthetic is for diesel engine drivers that prefer the higher-viscosity but still want the benefits of synthetic technology.

See Shell Rotella Products



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  • 1 month later...

I realize this post is a little old, but I wanted to give my input.

I purchased my 2012 Diplomat with a Maxxforce 10 in December 2017. It had 21,000 miles on it.  In August of 2018 I was in Camping World and they had an oil sample kit on the clearance rack.  I did a sample and the result indicated that the aluminum was high and I should change the oil.  
I changed the oil and put it Rotella T6 synthetic.  The coach had 27,000 miles on it then.  Since then, I’ve submitted samples and everything is good.  They say to drive 2500 miles and submit another sample.  After the last sample, they said to drive it 1,000 miles and submit a sample.  I decided that was long enough on the oil and filter - 6 years and 16,000 miles, so I changed it even though it was still testing good.  I used Rotella T6 again, since I had enough of it in the garage.  

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