Oil Change from conventional to synthetic

[Donalson]

2014 6.7 Cummings. The original oil, in the truck when I bought it, was a conventional 15W-40.
I’m wanting to go to Valvoline premium blue synthetic .
My question is is do I go with the same weight oil? And is it necessary to do a flush before I change over?
I always change my own oil but I have never gone to a conventional to synthetic.
Thank you.

 

[BossHogg]

From what I have read over the years, Cummins' are shipped with Pennzoil synthetic. Synthetic oil is required when operating in cold temperatures, I think it is zero and below.

I don't see any reason to "flush" the engine crankcase unless you are some sort of an extreme perfectionist.

 

[crash68]

^^^ what he said
Only thing you need to change from conventional to synthetic (or vice versa) oil is drain one and pour in the other.
Cummins/FCA does recommend using 5W-40 Full synthetic when the temps are going to be below 0°F

 

[Gr8bawana]

^^^ what he said
Only thing you need to change from conventional to synthetic (or vice versa) oil is drain one and pour in the other.
Cummins/FCA does recommend using 5W-40 Full synthetic when the temps are going to be below 0°F

On the subject of ambient temp and oil. Will matter if I have 15w40 when I go hunting for a week or two and the morning temps are below 0* but daytime temps are in the 30's? Should I have any concerns?

 

[crash68]

On the subject of ambient temp and oil. Will matter if I have 15w40 when I go hunting for a week or two and the morning temps are below 0* but daytime temps are in the 30's? Should I have any concerns?

If you know the freezing weather is coming, change the oil in advance. If you do have the heavier weight in, try to get the engine warmed up before getting on the skinny pedal. Unless your towing something considerably heavy you'll want to be using the winter front when the weather is starting to stay in the 30's.

 

[Gr8bawana]

If you know the freezing weather is coming, change the oil in advance. If you do have the heavier weight in, try to get the engine warmed up before getting on the skinny pedal. Unless your towing something considerably heavy you'll want to be using the winter front when the weather is starting to stay in the 30's.

So you're saying I should change my oil for a 2 week period? It's nowhere near that cold where I live, only where we go hunting.
I only ask because I'm totally new to the world of diesel and want my truck to last forever.

 

[crash68]

So you're saying I should change my oil for a 2 week period? It's nowhere near that cold where I live, only where we go hunting.
I only ask because I'm totally new to the world of diesel and want my truck to last forever.

I wouldn't go to that extreme, you can run the 5W-40 in warmer weather. If your next oil change is close to hunting season and you know most of the weather is going to be close 0F for the duration of that oil change, run the 5W-40. If you so encounter the really cold weather and still have the 15W-40 in the engine, be nice to the engine while it warms up. You can even run a synthetic 15W-40 as it flows better than conventional.
I wouldn't worry about running the 5W-40 even in normal comfortable temps unless I was going to really work the snot out of the truck(10K+ load through the mountains etc).

 

[Gr8bawana]

Thanks