Costco Kirkland brand diesel oil. Anyone know anything about it?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Gr8bawana

Senior Member
Joined
Dec 7, 2015
Posts
1,274
Reaction score
1,059
Ram Year
2017
Engine
6.7 CTD
I've used the Costco brand 15w/40 for the last 2 oil changes. I believe it was less than $38 for the 3 gallon box. It meets Cummins spec so there is no reason to spend any unnecessary $$ for name brand or synthetic oil.
Most people use synthetic oil simply because they believe it's "better" than dino oil and not because they live where the truck will be used in below 0° temps.
 

06 Dodge

Senior Member
Joined
Jan 4, 2022
Posts
1,900
Reaction score
1,781
Location
Forest Grove, Oregon
Ram Year
2022
Engine
6.7L CTD
I've used the Costco brand 15w/40 for the last 2 oil changes. I believe it was less than $38 for the 3 gallon box. It meets Cummins spec so there is no reason to spend any unnecessary $$ for name brand or synthetic oil.
Most people use synthetic oil simply because they believe it's "better" than dino oil and not because they live where the truck will be used in below 0° temps.
I lived where winter temps would see temps below zero, the selling dealer told me no reason to use 5w40 because the engine had a block heater o_O my UOA showed that Rotella T6 held up better then Delvac Dino oil in my truck, so my opinion is based on science and not belief...
 

BossHogg

Senior Member
Joined
Feb 23, 2014
Posts
1,932
Reaction score
2,443
Location
Oakland Township, Michigan
Ram Year
2015
Engine
6.7L Cummins
I lived where winter temps would see temps below zero, the selling dealer told me no reason to use 5w40 because the engine had a block heater o_O my UOA showed that Rotella T6 held up better then Delvac Dino oil in my truck, so my opinion is based on science and not belief...
What I am trying to understand is exactly what held up better between T6 and the Delvac? I'm assuming you followed the maintenance schedule.

I've run T6, and conventional my 2015 Cummins, I follow the scheduled maintenance for oil and filter changes. I've had UOAs done on both conventional and synthetic and there were no notable differences, both UOAs show the oil had a good deal of life available. I would get about 12 to 14 thousand miles before the oil life meter got down to under 15%, that is when I would change the oil and filter.

Excluding my 2022 ED, I run T6 5w-40 in the Cummins because of cold weather operation, I also run the same in my Kubota RTV since it plows snow in the winter. For the tractors and the diesel lawn mower, I run Kirkland 15w-40 since these machines run in the warmer months. These machines get an oil change about every other season or about 150 to 200 hours of operation. Kubota calls for an oil change after 400 hours of operation or yearly.
 

06 Dodge

Senior Member
Joined
Jan 4, 2022
Posts
1,900
Reaction score
1,781
Location
Forest Grove, Oregon
Ram Year
2022
Engine
6.7L CTD
What I am trying to understand is exactly what held up better between T6 and the Delvac? I'm assuming you followed the maintenance schedule.

I've run T6, and conventional my 2015 Cummins, I follow the scheduled maintenance for oil and filter changes. I've had UOAs done on both conventional and synthetic and there were no notable differences, both UOAs show the oil had a good deal of life available. I would get about 12 to 14 thousand miles before the oil life meter got down to under 15%, that is when I would change the oil and filter.

Excluding my 2022 ED, I run T6 5w-40 in the Cummins because of cold weather operation, I also run the same in my Kubota RTV since it plows snow in the winter. For the tractors and the diesel lawn mower, I run Kirkland 15w-40 since these machines run in the warmer months. These machines get an oil change about every other season or about 150 to 200 hours of operation. Kubota calls for an oil change after 400 hours of operation or yearly.
Thought I was answer this before I head out of town. At 6 months the Dino oil had a TBN of 3.x on T6 the lowest TBN I had was 3.x that was after 12 months of usage that alone is enough proof that Dino oil does not hold up as well as synthetic oil in my old 06 CTD and the small extra cost for synthetic was still less then what I would of paid for 2 Dino oil changes.
 
OP
OP
Oliver Closehauf

Oliver Closehauf

Senior Member
Joined
Nov 21, 2020
Posts
718
Reaction score
457
Location
Cincinnati
Ram Year
2005 Laramie
Engine
Cummins 5.9
So the point of my original post was I will drive my truck at most 1000 miles a year. If I drive it more than that I drove the **** out of it. I work from home, all major home improvement stores are under 20 miles away with Home Depot and Lowes being 5-7 miles. I don't have an RV or boat and I don't tow anything (But I can if I ever need to). I used the Cummins recommended Valvoline dino in it last year and ordered it again this year.

Because of the expected low milage, I was more concerned about time being limiting factor. How the Kirkland holds up over time, not mileage. Did I really need to spend extra for 1000 miles a year. But as I said, I did go ahead pay the extra for the Valvoline. It's what the guys before me used and at 275K I figured that's success I probably shouldn't mess with.
 

BossHogg

Senior Member
Joined
Feb 23, 2014
Posts
1,932
Reaction score
2,443
Location
Oakland Township, Michigan
Ram Year
2015
Engine
6.7L Cummins
So the point of my original post was I will drive my truck at most 1000 miles a year. If I drive it more than that I drove the **** out of it. I work from home, all major home improvement stores are under 20 miles away with Home Depot and Lowes being 5-7 miles. I don't have an RV or boat and I don't tow anything (But I can if I ever need to). I used the Cummins recommended Valvoline dino in it last year and ordered it again this year.

Because of the expected low milage, I was more concerned about time being limiting factor. How the Kirkland holds up over time, not mileage. Did I really need to spend extra for 1000 miles a year. But as I said, I did go ahead pay the extra for the Valvoline. It's what the guys before me used and at 275K I figured that's success I probably shouldn't mess with.
There is no direct answer to your question. Oil is a refined product and various companies make oil additives. A brand will pick and choose the additives and additive amounts to the oil they buy from the refineries.

All anyone can do is share their experiences with the various brands. Oil is likely one of the most debated topics on any forum that talks about engine oils. Currently, I run 1 gasoline car, 2 gasoline marine engines, 2 diesel trucks, and three diesel land management machines. I used the recommended oil specifications (not the brand names) and follow the recommended maintenance schedules. I buy the oil I can find and if on sale even better.

In the end, the machine I put oil in will be long gone and replaced well before any difference is detected from the oil brand name.
 
Last edited:

BossHogg

Senior Member
Joined
Feb 23, 2014
Posts
1,932
Reaction score
2,443
Location
Oakland Township, Michigan
Ram Year
2015
Engine
6.7L Cummins
Thought I was answer this before I head out of town. At 6 months the Dino oil had a TBN of 3.x on T6 the lowest TBN I had was 3.x that was after 12 months of usage that alone is enough proof that Dino oil does not hold up as well as synthetic oil in my old 06 CTD and the small extra cost for synthetic was still less then what I would of paid for 2 Dino oil changes.
Before we switched over to ultra-low sulfur diesel fuel, TBN was used to neutralize the high-sulfur fuels which generated significant amounts of sulfuric acid in the engine oil. Now with ultra-low sulfur fuels, TBNs are much lower in UOAs. I don't think, from what I've read and understood, TBN has much value in Tier 4 final engines which yours isn't. In my case, TBNs are not the focus instead the oil analysis is focused on wear, oxidation, viscosity, TAC (total acid number).
 
Top