Question Which oil for Cummins ISL 9 and ONAN 8K?

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Neal

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I went to Amazon to buy more oil after redoing the oil change in my ONAN and see there are different versions of the Duralec SAE 15W40. Before I order more which oil is the preferred for topping off the Cummins ISL 9 and also for the ONAN 8K?
 

Neal

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Neal

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redbaron

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I use Shell Rotella 15w40 on all my diesel engines. Usually the T4, but no problem using the T1. Whichever is on sale at the time.
 

Chuggs

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My Dodge 2500 was fed a consistent diet of Shell Rotella T 15W-40...using that in my Onan.

The engine...I’m sticking with Valvoline Premium Blue Heavy Duty Diesel 15W-40.

Not a petro-chemical pro by any means.
 

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Pineapple juice
 

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RUM...is this word association?
 

"EZ"

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I've been selling commercial diesel trucks for 30 years. I'm sold on Shell Rotella 15W40 after seeing the inside of an engine they put a million miles on at a show. It was so clean inside you wouldn't believe it. :) (y)
 

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I tend to like synthetic type oils. They adhere to metal and help prevent dry starts and they are slipperier then conventional oils reducing heat in the engine. With a very clean running engine it is great. Diesels/Aircraft engines are not that clean. Both are high compression and use a somewhat dirty fuel. Aircraft fuel still has lead in it and are high compression. With this dirty fuel will come contamination to the oil when deposits blow by the rings of the cylinder. The bad thing about synthetic oils is it does not suspend the contaminates in the oil very well. These contaminates will settle somewhere in the engine i.e. oil pan etc. Diesel specific oils are designed to suspend those contaminates to when you do oil changes they are flushed with the oil if not trapped by the filter. That is why a synthetic blend oil comes in handy. You get the contamination suspension you need and the benefits of the synthetic i.e dry starts etc. There is also synthetic additives you can add the your favorite oil like Rotella. "slick 50" for example.
 

Webz

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When I bought our DS, I called Gafney Freightliner and asked what oil came in the engine when new. I was told Rotella.
Got thinking about it and it is a Cummins engine.
Contacted Cummins and they said when the engine left their plant, it had Valvoline Blue conventional oil it.
I sent a sample to Blackstone lab. Told them it was either Valvoline or Rotella. They analyzed the oil and said it was Valvoline due to it having titanium in it.
While at Gaffney, I noticed they use Rotella.
Rotella is easier to find while traveling but I've only put Valvoline Blue in my engine. When I see it on sale, usually at ORieily's, I pick up 8 gallons.
Sometimes you have to ask the right person to get the correct answer.
 
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