Chevy and GMC Duramax Diesel Forum banner

1 - 20 of 33 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter #1
My 2020 Duramax asks for 15w 40 full synthetic, at my local auto parts store they only had rotella T6 in 5w 40. I bought 10 quarts of the 5w 40 and changed my oil, have I any need for concern because I did not run 15w40?
 

·
Registered
Joined
·
14 Posts
Discussion Starter #3
Thank you, I was concerned that it would not get the proper lubrication throughout the engine.
 

·
Premium Member
Joined
·
324 Posts
Manual says 15W-40 and 5W-40 @ zero f and below. See the bottom of the second page that emmitt attached.
 

·
Premium Member
Joined
·
4,545 Posts
the first number, (5 or 15) is the viscosity of the oil when cold. The secondnumber, 40 is the viscosity of the oil when it is warm. NO it does not thicken but it only thins down to what 40 weight oil would be at operating temps

Shell just introduced the 15W-40 oil, undoubtedly due to customer demand.

Even here in the hot south I run 5W40 all year long with no ill effects whatsoever. In fact, the thinner oil, at startup, is more easily moved through the engine to lubricate it. For that reason I believe the 5W-40 to be the better product
 

·
Registered
Joined
·
465 Posts
Just curious as to why you would first change the oil, then come here to ask if it was if it was going to cause issues? IDK, seems backwards to me:unsure:
 

·
Registered
Joined
·
14 Posts
Discussion Starter #7
yes it is backwards,
I thought it would be ok but just wanted to make sure. If it wasn’t I Don think I would have done a lot of damage in the short period of time I have had the new oil in the engine
 

·
Registered
Joined
·
86 Posts
Using 5W-40 it's perfectly acceptable and what I plan to switch to on my next oil change. I'll be using this year round.
 

·
Registered
Joined
·
9 Posts
I have noticed a slight mileage difference on the 5W40. I run AMZOIL 5W40 pretty much year round but do oil analysis with Blackstone at each change (5000 miles). In 60,000+ miles there seems to be a difference in the amount of iron, etc. in the oil if I go over 5,000 miles. I never exceed 6,000 miles regardless. A bit expensive but cheaper than an engine. I've done the long drain interval thing but not on the Duramax.
 

·
Registered
Joined
·
11 Posts
I have noticed a slight mileage difference on the 5W40. I run AMZOIL 5W40 pretty much year round but do oil analysis with Blackstone at each change (5000 miles). In 60,000+ miles there seems to be a difference in the amount of iron, etc. in the oil if I go over 5,000 miles. I never exceed 6,000 miles regardless. A bit expensive but cheaper than an engine. I've done the long drain interval thing but not on the Duramax.
I run theT-6 and get Blackstone oil samples every other change. I am currently going 25,000 miles between changes and have over 975,000 miles on my 2011. Blackstone keeps telling me to go farther between changes. The most I have went was 27,000 and it was still good to go farther according to them.
 

·
Registered
Joined
·
86 Posts
I have noticed a slight mileage difference on the 5W40. I run AMZOIL 5W40 pretty much year round but do oil analysis with Blackstone at each change (5000 miles). In 60,000+ miles there seems to be a difference in the amount of iron, etc. in the oil if I go over 5,000 miles. I never exceed 6,000 miles regardless. A bit expensive but cheaper than an engine. I've done the long drain interval thing but not on the Duramax.
Wear metals such as iron as measured on oil analysis will always increase with more miles. I believe the best way to manage this is to total the wear metals and divide that by the number of miles in thousands. By doing that you can start to get a feel for whether the rate of wear is actually increasing with higher mileage.
 

·
Registered
Joined
·
59 Posts
My 2020 Duramax asks for 15w 40 full synthetic, at my local auto parts store they only had rotella T6 in 5w 40. I bought 10 quarts of the 5w 40 and changed my oil, have I any need for concern because I did not run 15w40?
OEM will always test and specify the lowest quality oil so they can sell the engine around the world without problems with oil quality. In this case they will use oil that has a crude oil component which means it is limited as to what viscosity range can be blended. Bottom line is 5w40 will be fine if not better than 15w40.
 

·
Registered
Joined
·
59 Posts
I run theT-6 and get Blackstone oil samples every other change. I am currently going 25,000 miles between changes and have over 975,000 miles on my 2011. Blackstone keeps telling me to go farther between changes. The most I have went was 27,000 and it was still good to go farther according to them.
Most people over change their oil. Unless there is an issue oil does not change, just gets dirty, so a mid cycle oil filter change for high mileage is the normal practice. Still makes roll with laughter when I go to a dealer for an oil change and GM says 10,000 miles and the dealer plasters a label that says 3000 miles. When asked, they basically say GM does not have a clue and they know better, well they know how to make more money.
 

·
Registered
Joined
·
1,027 Posts
My 2020 Duramax asks for 15w 40 full synthetic, at my local auto parts store they only had rotella T6 in 5w 40. I bought 10 quarts of the 5w 40 and changed my oil, have I any need for concern because I did not run 15w40?
Are you kidding? You would use a lower viscosity oil in a diesel engine and then ask it this was a smart move. 2017 and later engines are designed to work with the API FA-4 motor oils that were formulated and tested extensively over a period of years. Why would someone spend $60,000 on a new truck and then not use the motor oil specified by the manufacturer?

Buy the correct motor oil and get the oil in the truck changed along with the fuel filter as soon as possible.

For more details see this web page: What is PC-11? What You Need to Know About PC-11, CK-4, and FA-4 Diesel Engine Oil
 

·
Registered
Joined
·
155 Posts
Are you kidding? You would use a lower viscosity oil in a diesel engine and then ask it this was a smart move. 2017 and later engines are designed to work with the API FA-4 motor oils that were formulated and tested extensively over a period of years. Why would someone spend $60,000 on a new truck and then not use the motor oil specified by the manufacturer?

Buy the correct motor oil and get the oil in the truck changed along with the fuel filter as soon as possible.

For more details see this web page: What is PC-11? What You Need to Know About PC-11, CK-4, and FA-4 Diesel Engine Oil
Seriously?
 

·
Registered
Joined
·
59 Posts
The only lower viscosity is at cold temp, so during cold starts you get faster oil pressure and less wear. At normal operating temps it is the same hence the 40 designation in both. All OEM's test with the lowest quality oil they can, so they can sell the engine literally all over the world, with many places not having access to high cost synthetic oil. 5w40 oil will be fine, it is not about viscosity it is about lubrication. In fact most new engines have load sensitive oil relief valves so at low load you run much less oil pressure as it saves on fuel economy.
 

·
Registered
Joined
·
155 Posts
Here’s a member with over a million miles using Rotella T6. Million Mile LB7 Journey

Read your manual; it’s usually found in the glove box. 5w40 will be fine. My opinion is to stop picking fly crap out of pepper. Drive more, worry less.
 

·
Registered
Joined
·
86 Posts
The T6 5W-40 is a great oil. Use it and sleep well. I just had my last free oil change today. The next oil that will be going in is T6.
 

·
Registered
Joined
·
59 Posts
T6 is the best diesel oil around. It is actually made by Lubrizol in Cleveland and they have extensive chemical labs and dynos to back up the quality of the product.
 
1 - 20 of 33 Posts
Top