Probably Overthinking

W

W9HDG

Joined
May 29, 2016
Messages
72
Location
WI
Ok so I'm doing it. I'm going to ask the question that has been on my mind for a while. I will even predict the answer to be "just run 5w40 year round, you'll be fine" but that won't actually be the answer to the question I am going to ask.

I recently purchased a 2016 Nissan Titan XD with the Cummins diesel in it. While reading the owners manual (we all RTFM right?) I noticed that for all temperatures above -10F the recommended oil is 10w30 CJ-4. For temperatures below -10F up to 68F they recommend a 5w40 for easier starting, etc.

Now to the question...(no it isn't what oil should I use but if you want to include that in your answer go for it)...Why? Why would a manufacturer recommend 10w30 for all temperatures above -10F and yet limit the heavier, thicker, oil to a max temperature of 68F? I'm sure I would be fine running 5w40 all year, but I am that sort of person that tries to understand things and the reasoning behind them and I just can't wrap my head around it.

My closest servicing dealership is over 100 miles away. I gave them a call, and the 1st thing they told me is they won't work on them because there isn't the demand and they don't have a diesel tech. Then the service guy went and talked to the tech and came back with the generic "follow the owners manual" answer.

Again, I'm not really looking for a recommendation of weight, brand, etc., more looking to understand the reasoning behind the recommendation as published by Nissan/Cummins.

Thanks,

~Travis

PS - I should add that this is my first diesel so I'm still learning in that regards so I will appreciate recommendations even if it isn't what I'm ultimately asking.
 
@W9HDG I would probably consider the 10w30 unless you use the truck for heavy towing or something like that. I experienced shearing in my truck when using 5w40. You could also consider a 10w40 if you tow heavy. I think you would want the 40 weight in the summer for better protection.

FWIW, I use 15w40 in my Cummins year round. I tow an 11k travel trailer and keep my truck in the garage. In the winter I won’t drive it if the daytime high is below 5F.

Being your first diesel fuel filtration is key. Change your fuel filter at the recommended intervals to avoid issues.

Just my $0.02
 
The manual makes perfect sense. 5w-x for colder temps & 10w-x for hotter temps. You're looking at the high end 30 vs 40 but that is not what cummins/Nissan are looking at. They are putting more emphasis on the starting temp viscosities 5w vs 10w. I suffer from the same issue...overthinking.
 
fantastic said:
The manual makes perfect sense. 5w-x for colder temps & 10w-x for hotter temps. You're looking at the high end 30 vs 40 but that is not what cummins/Nissan are looking at. They are putting more emphasis on the starting temp viscosities 5w vs 10w. I suffer from the same issue...overthinking.
Click to expand...
Fantastic, your response is well...fantastic. You brought up what I didn't consider. That it wasn't about the thick weight but the thin weight and there probably isn't a 5w30 diesel oil that meets Nissan/Cummins requirements.
 
W9HDG said:
Fantastic, your response is well...fantastic. You brought up what I didn't consider. That it wasn't about the thick weight but the thin weight and there probably isn't a 5w30 diesel oil that meets Nissan/Cummins requirements.
Click to expand...
Thank you & I'm happy to hear that it makes more sense now. Have a great evening!
 
tnt_motorsports said:
@W9HDG I would probably consider the 10w30 unless you use the truck for heavy towing or something like that. I experienced shearing in my truck when using 5w40. You could also consider a 10w40 if you tow heavy. I think you would want the 40 weight in the summer for better protection.

FWIW, I use 15w40 in my Cummins year round. I tow an 11k travel trailer and keep my truck in the garage. In the winter I won’t drive it if the daytime high is below 5F.

Being your first diesel fuel filtration is key. Change your fuel filter at the recommended intervals to avoid issues.

Just my $0.02
Click to expand...
Thank you for reminding me about filtration. The truck as serviced just before I bought it so I don't plan to change filters until this fall when I figure the filters will have about 5k on them but I would rather go into winter with clean filters because I will likely drive the truck less than 10k a year.
 
I’m kinda in the same predicament. Ram says above 0* use 10-30. Below 0* use 5-40. It’s not going to be anywhere close to 0* around here and I’m not going to be anywhere that it gets that cold. I asked the local dealer and he said 5-40. The 10-30 is thicker cold and thinner when hot than the 5-40 at both extremes. I’m going with R T6 5-40 per various recommendations.
 
W9HDG said:
Thank you for reminding me about filtration. The truck as serviced just before I bought it so I don't plan to change filters until this fall when I figure the filters will have about 5k on them but I would rather go into winter with clean filters because I will likely drive the truck less than 10k a year.
Click to expand...
No problem. Being a Cummins I would try to stick with Fleetguard for filtering. They are the OEM for Cummins.

Just my $0.02
 
OLEJOE said:
I’m kinda in the same predicament. Ram says above 0* use 10-30. Below 0* use 5-40. It’s not going to be anywhere close to 0* around here and I’m not going to be anywhere that it gets that cold. I asked the local dealer and he said 5-40. The 10-30 is thicker cold and thinner when hot than the 5-40 at both extremes. I’m going with R T6 5-40 per various recommendations.
Click to expand...
Then just split the difference and use a good CK4 15w40.
 
I'll take all the "thinner" I can get when the high air temperature is -25*
 
W9HDG said:
Ok so I'm doing it. I'm going to ask the question that has been on my mind for a while. I will even predict the answer to be "just run 5w40 year round, you'll be fine" but that won't actually be the answer to the question I am going to ask.

I recently purchased a 2016 Nissan Titan XD with the Cummins diesel in it. While reading the owners manual (we all RTFM right?) I noticed that for all temperatures above -10F the recommended oil is 10w30 CJ-4. For temperatures below -10F up to 68F they recommend a 5w40 for easier starting, etc.

Now to the question...(no it isn't what oil should I use but if you want to include that in your answer go for it)...Why? Why would a manufacturer recommend 10w30 for all temperatures above -10F and yet limit the heavier, thicker, oil to a max temperature of 68F? I'm sure I would be fine running 5w40 all year, but I am that sort of person that tries to understand things and the reasoning behind them and I just can't wrap my head around it.

My closest servicing dealership is over 100 miles away. I gave them a call, and the 1st thing they told me is they won't work on them because there isn't the demand and they don't have a diesel tech. Then the service guy went and talked to the tech and came back with the generic "follow the owners manual" answer.

Again, I'm not really looking for a recommendation of weight, brand, etc., more looking to understand the reasoning behind the recommendation as published by Nissan/Cummins.

Thanks,

~Travis

PS - I should add that this is my first diesel so I'm still learning in that regards so I will appreciate recommendations even if it isn't what I'm ultimately asking.
Click to expand...
Nissan supposedly sold 1in 8 Titans with the Cummins Diesel. The biggest issue was from what I read Cummins had a different engine in mind but it didn't fit and the one used was down on power. Couple that with the 4 speed automatic transmission instead of a 5-6 speed and it suffered. However you might have to find a Semi truck shop for repairs. Jeep owners and to some extent Mazda Rotary owners like myself have had to dig when companies don't get fully behind a product. Jeep offered a diesel option on some grand Cherokees and commanders from an Italian company. Unfortunately many jeep dealerships didn't have anyone who could repair them.
 
97prizm said:
Nissan supposedly sold 1in 8 Titans with the Cummins Diesel. The biggest issue was from what I read Cummins had a different engine in mind but it didn't fit and the one used was down on power. Couple that with the 4 speed automatic transmission instead of a 5-6 speed and it suffered. However you might have to find a Semi truck shop for repairs. Jeep owners and to some extent Mazda Rotary owners like myself have had to dig when companies don't get fully behind a product. Jeep offered a diesel option on some grand Cherokees and commanders from an Italian company. Unfortunately many jeep dealerships didn't have anyone who could repair them.
Click to expand...
don't forget the liberty's came with diesel option too. :)
 
97prizm said:
Nissan supposedly sold 1in 8 Titans with the Cummins Diesel. The biggest issue was from what I read Cummins had a different engine in mind but it didn't fit and the one used was down on power. Couple that with the 4 speed automatic transmission instead of a 5-6 speed and it suffered. However you might have to find a Semi truck shop for repairs. Jeep owners and to some extent Mazda Rotary owners like myself have had to dig when companies don't get fully behind a product. Jeep offered a diesel option on some grand Cherokees and commanders from an Italian company. Unfortunately many jeep dealerships didn't have anyone who could repair them.
Click to expand...
There definitely isn't many of them around and I knew I might have a hard time finding service when I bought it because of its rarity. The one I bought had a new engine put in under warranty at 75K miles in 11/2020 it should have all the updated parts (crank, etc). There are a few things that I'm a little concerned about in terms of getting it serviced like getting the turbo actuator calibrated if/when I need to put a new one in but I'll cross that bridge when I get to it. I'm seeing some signs of 3rd party tools that can access the calibration stuff so hopefully that will be a solution.
 
tnt_motorsports said:
@W9HDG I would probably consider the 10w30 unless you use the truck for heavy towing or something like that. I experienced shearing in my truck when using 5w40. You could also consider a 10w40 if you tow heavy. I think you would want the 40 weight in the summer for better protection.

FWIW, I use 15w40 in my Cummins year round. I tow an 11k travel trailer and keep my truck in the garage. In the winter I won’t drive it if the daytime high is below 5F.

Being your first diesel fuel filtration is key. Change your fuel filter at the recommended intervals to avoid issues.

Just my $0.02
Click to expand...
What causes shearing in a slightly heavier weight oil? Is it the 5W part or the 40?
 
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