Chevy and GMC Duramax Diesel Forum banner

1 - 20 of 117 Posts

·
Registered
Joined
·
881 Posts
Discussion Starter #1
So I need to do an oil change. I have been taking my truck to places in the past simply due to the fact that I didn't have a catch pan big enough to catch the oil. So I finally bought one, and for my first oil change decided to run the Rotella T5 conventional/Synthetic blend. Now its time to do another change (I daily drive my truck 60miles a day minimum to work) and I'm wanting to switch to full synthetic to extend the change intervals.

Upon going to the parts store to get oil, the only weight of the synthetics (regardless of brand they carried) were all 5w-40 vs the 15w-40 they carry in traditional oils. Now I understand the difference between lighter and heavier weights in conventional oils, but don't know if that logic changes when running full synthetic.

I bought the Wix XP (or was it XD) oil filter that is designed for 10k mile intervals, and plan to change the oil between 7500-10k miles depending on use. Anyone see any issue with this?

Truck is a 2006 LBZ, with 106k miles on it. I tow a 10-11k 5th wheel 4-5 times a year, otherwise daily drive in a commute situation. I live in the Pacific NW, so generally mild weather - never too hot, or too cold. Thanks for the advice.
 

·
Registered
Joined
·
90 Posts
Been running 5W-40 syn since I bought my lml. I wouldn’t use it in a built engine but in a DD it’s good. AFAIK there is no such thing as a 15w-40 syn anymore. If there ever even was.
 

·
Registered
Joined
·
274 Posts
I have been running 5 w40 Mobil 1 since 125,000 on an Lly currently sitting at 160,000. My truck is used similar to yours.

You will find many are running 5w40 with no issues.
 

·
Registered
Joined
·
2,754 Posts
Amsoil has 15W40, at any rate 10k mile intervals should be fine, however, best way to know for sure is oil analysis....


:popcorn
 

·
Registered
Joined
·
90 Posts
Amsoil has 15W40, at any rate 10k mile intervals should be fine, however, best way to know for sure is oil analysis....





:popcorn


Amsoil isn’t real oil lol.

I’m changing mine around 2000 miles after the oil change notification comes on. Usually run Mobil or Chevron but if it’s from any of the big oil companies I feel you can’t go wrong.
 

·
Registered
Joined
·
125 Posts
Ive been using Delo 400 XSP Synthetic 5W-40 since I bought the truck (LBZ) at 84K miles, only had the truck for 4 mo thought. But I switch to 5w-40 on my Ford 7.3l, its spin over quicker cold and no difference in oil pressure. Synthetic oil is generally thinner on the first number.
 

·
Registered
Joined
·
881 Posts
Discussion Starter #7
Thanks guys. I figured it was ok just wanted to confirm.
 

·
Registered
Joined
·
2,662 Posts
The first number is the relative viscosity at 0 degrees and the second number is the relative viscosity at 212 degrees. Relative is the important word. All oil is thicker when cold than when hot. What really counts is the viscosity when warmed up and going down the road. The engine is designed to work with a certain viscosity under those conditions. All other conditions are a compromise that the engine can tolerate but doesn't prefer. If it could be arranged the oil would be the same viscosity all of the time. That is a dream though.

The closer we can get to constant viscosity the better so that the engine can be optimized for that condition. Our engines are designed to work with oil that is the viscosity of 40 weight oil at 212 degrees. 5W-40, 0W-40 and 15W-40 oils are all the same viscosity (more or less) at operating temperature. They are all thicker at cooler temperatures than they are at operating temperature. 0W-40 doesn't thicken up as much as it cools off as 15W-40 does. 5W-40 is between the other two when it is cold.

Synthetic oil has an inherently more stable viscosity profile than dino oil because the engineers chose and manufacture molecules that have better properties than nature makes. I don't believe you could find a synthetic oil that was a straight 30 weight. They just don't make it. I believe that the worst you could find would be something like 20W-40 and that would be pure base stock with no additives. By adding things to the oil base stock it becomes 5W-40 pretty easily. Since that is better for our engines than 15W-40 that is what they do.

15W-40 was never purely a viscosity based rating. It has always been more of a "diesel" oil designation. I don't believe anybody ever made gasoline engine oil with that rating. 15W-40 oil had more detergents and dispersants in it to handle diesel soot than gasoline engine oils and lacked some of the things gasoline engines needed. It has become a somewhat outdated spec.

In the viscosity rating scale there is some overlap. For instance, it is possible to make an oil that is both 10W-40 and 5W-40 at the same time. I think this is why there never was any call for 15W-40 gasoline engine oil. That viscosity range is covered by 10W-40 and 20W-40 which is more familiar to the public.

There is no harm in using an oil with a low first number. It will always be thicker when cold than would be ideal. It would just be less too thick than an oil with a higher first number. It is the second number that matters the most because it describes the normal condition of the oil when the engine is normally warmed up.

Before synthetics were popular (they have been around since the dawn of jet engines) refiners tried to extend the viscosity range of oils with lots of additives. In doing so they made the oil's quality very dependent on the additives. Since additives tend to go away quickly, relying too heavily on them makes the oil fragile. Earlier broad range oils tended to get very thick or very thin if not changed often. With today's synthetics there is less reliance on additives so the oil tends to be more stable and last much longer. Engine oil technology is a marvel of modern engineering.
 

·
Premium Member
Joined
·
4,416 Posts
So I need to do an oil change. I have been taking my truck to places in the past simply due to the fact that I didn't have a catch pan big enough to catch the oil. So I finally bought one, and for my first oil change decided to run the Rotella T5 conventional/Synthetic blend. Now its time to do another change (I daily drive my truck 60miles a day minimum to work) and I'm wanting to switch to full synthetic to extend the change intervals.

Upon going to the parts store to get oil, the only weight of the synthetics (regardless of brand they carried) were all 5w-40 vs the 15w-40 they carry in traditional oils. Now I understand the difference between lighter and heavier weights in conventional oils, but don't know if that logic changes when running full synthetic.

I bought the Wix XP (or was it XD) oil filter that is designed for 10k mile intervals, and plan to change the oil between 7500-10k miles depending on use. Anyone see any issue with this?

Truck is a 2006 LBZ, with 106k miles on it. I tow a 10-11k 5th wheel 4-5 times a year, otherwise daily drive in a commute situation. I live in the Pacific NW, so generally mild weather - never too hot, or too cold. Thanks for the advice.
Only problem I see is that Wix filter. Better a Baldwin B1441 or a Moblie M1-303.

Some on here have described problems they had with the Wix filters.
 

·
Registered
Joined
·
69 Posts
Amsoil isn’t real oil lol.
So I've been using fake oil for the past 60k miles? Wow that's crazy. Amazing it's still running lol
 

·
Registered
Joined
·
9 Posts
I just changed my oil today in my 08 LMM which I bought a month ago with only 60k miles on it. Don't know what was in it when I got it, but its last service was at the dealer. Anyway, I used Lucas 15w-40 full synthetic and a Mobil1 filter. I got 3 gallons of oil from Autoplicity for $70 including shipping and the filter for $19 from Amazon.
 

·
Registered
Joined
·
105 Posts
I've run nothing but Mobil 1 5W-40 Diesel oil in my 2005 3500 Dually, then my 2011 3500 Dually, and now my 2018 3500 Dually and tow Heavy
19 - 20K with no problems or issues.
 

·
Registered
Joined
·
2,662 Posts
So I've been using fake oil for the past 60k miles? Wow that's crazy. Amazing it's still running lol
Actually from a certain point of view Amzoil is fake oil. Most synthetic oils are made from petroleum feed stock that is broken up into small molecules that are then combined into desirable larger molecules. Amzoil starts life as an alcohol which is then combined to form desirable larger molecules. For that much then Amzoil is fake. It's a pretty good fake though.

If you want to insist that only oil that started out as a fossil is real then a lot of oils are fake. For example, corn oil, olive oil, canola oil and whale oil were never in the ground. No not even as minerals because they are hydrocarbons and the hydrogen comes from water while the carbon comes from CO2. Ok, the water was in the ground for a little while at least.

Actually, any substance that has an oily consistency and feel can rightly be called oil. What difference does it make though? As long as it does the job, use it.
 

·
Registered
Joined
·
9 Posts
So, after spending $19 for the Mobil1 filter on Amazon, I walk into my local O'Reilly store and see it on the shelf for $14. Live and learn I guess...
 

·
Registered
Joined
·
1,230 Posts
Add me to the list. I run Mobil Turbo Diesel Truck 5W40 (full synthetic) in my L5P and it hasn't complained. Granted, I don't have that many miles on it yet.
 

·
LHN...We ARE the Joneses
Joined
·
26,254 Posts
Amazoid is no longer a bargain source....for anything

So, after spending $19 for the Mobil1 filter on Amazon, I walk into my local O'Reilly store and see it on the shelf for $14. Live and learn I guess...
If ya don't wanna feel worse....don't stroll to the back corner next time you're at Wally's place.....and see it for $9.97 :nerd:
 
1 - 20 of 117 Posts
Top