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Was in Costco this morning and for the first time at our store I saw 15W-40 HD diesel oil. Says it meets API-CK4 specs for diesels. Anyone have experience wit this oil? $36 for 3 gallons is hella deal these days.

Bob
 

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I've seen this in my Costco for about a year now. I'm sure it's a quality oil but it's not synthetic and it's not 5w-40 which is recommended for our engine. If they had a Kirkland Signature Synthetic 5w-40 diesel oil I'd be willing to try it.
 

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Yeah that's cheap. Might be OK oil but, you can get 2.5 Gal of Mobil Delvac 1 ESP 5W-40 at Tractor Supply for $60 and there is normally a rebate. The recent rebate that ended May 31st was a $17.50 Visa card on a 2.5 gallon jug and $7 on a gallon jug.
 

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I have run and am currently running 15w40 synthetic with no issues. It was all I could find. Back several years ago GDE stated these engines were designed around 15w 40 so shouldn’t be an issue running it at all
 

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I have run and am currently running 15w40 synthetic with no issues. It was all I could find. Back several years ago GDE stated these engines were designed around 15w 40 so shouldn’t be an issue running it at all
Running thicker oil contributes to your less than stellar fuel economy. There may only be a 1% - 2% decrease in fuel economy, but that adds up with today's fuel prices!
 

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Running thicker oil contributes to your less than stellar fuel economy. There may only be a 1% - 2% decrease in fuel economy, but that adds up with today's fuel prices!
I ran 15w40 and 5w40 both with the old GDE and new GDE. The old tune just plane got about 2 mpg better. Between the two weights of oil I see no notable fuel mileage difference. I have realized a change in my driving habits as a big part of the fuel mileage and since reverted back to my old driving style. On the old GDE I averaged around 28-30 on the new I average 25-27 after pulling my toes out of the injection pump.
 

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I have run and am currently running 15w40 synthetic with no issues. It was all I could find. Back several years ago GDE stated these engines were designed around 15w 40 so shouldn’t be an issue running it at all
Ram had a good reason for changing from 15w-40 to 5w-40 Full Synthetic in Aug 2016 (Svc Bulletin 18-087-16 REV. A)
You won't see or experience any issues with 15w-40 until it grenades. That said, you may have a better assembled Eco and it may last forever. Hoping it's the latter.
 

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Ram had a good reason for changing from 15w-40 to 5w-40 Full Synthetic in Aug 2016 (Svc Bulletin 18-087-16 REV. A)
The service bulletin (18-087-16 REV. A) changed the recommendation from 5W-30 to 5W-40.
 

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Ram changed from 5w30 to 5w40?
Correct. When I bought my 2015, it had 5W-30 in it. Before I drove it off the lot, the dealer changed the oil to T6. The switch was made somewhere in midyear of 2016.
 

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The service bulletin (18-087-16 REV. A) changed the recommendation from 5W-30 to 5W-40.
You are correct. My error, got it backwards. Thanks for the heads up
 
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