10w40 or 5w30 for the winter?

[0burb8]

I'm about to do an oil change soon on my 2003 Silverado LB7 diesel. It gets occasionally down to -25°c where I live.

I can't decide what to do. I have free access to 5w30 and 10w40 Motul Tekma+ oils. Using 5w30, cold start lubrication is not a problem, but the viscosity is thinner at operating temp.
Using 10w40, cold start lubrication could be a problem, but the viscosity is what the engine calls at operating temp.
It's a small sacrifice both ways.

Please help and point me in the right direction.

 

[fantastic]

With that vintage and being a diesel 10w-40 is preferable & since it's only occasionally that low temperature.

 

[JavierH19]

I presume you don't have a heater?

10w is rated to be good down to -30c or -22f and 5w is rated to be good down to -35c or -31f.

And how do you get free access to those oils. Sounds like a sweet thing to have going.

You could use 10w-40 or a mix if you want it to start a bit easier.

I'd only use straight 5w30 if engine oil temp never gets above 190f. If your engine oil temps are below roughly 190f/88c at peak then I'd use only 5w30 since at that temp it's about as thick as a fully warmed 40 grade.

 

[Jetronic]

I would use 10W-40 but pay attention to the forecast: if I had concerns about the temperatures coming up, I'd replace some 10W-40 with 5w30. I have a pump to suck oil through the dipstick, it wouldn't bve a complete oil change though. And if topping up was needed, I'd likely use 5w30 aswell.

 

[0burb8]

I do have a heater. It heats the coolant. It has little to none effect on the oil, but sure it's better than nothing. Could go with 5w40 but I don't want to spend any money on oil when I can get it for free.
One thing that I thought of, is making a mix of those 2 oils I mentioned.

 

[JavierH19]

I do have a heater. It heats the coolant. It has little to none effect on the oil, but sure it's better than nothing. Could go with 5w40 but I don't want to spend any money on oil when I can get it for free.
One thing that I thought of, is making a mix of those 2 oils I mentioned.

Do you know what your peak oil temps are in this cold. That's the more important thing.

 

[kschachn]

An oil with a 10W winter rating is appropriate for starting down to about 0F or so. Below that and down to about -30 then use one with a 5W winter rating.

It would be foolish to use an oil with a 10W rating at -25. If you’re really worried about the HT/HS of the 30-grade at operating temperature then use a 5W-40.

Easy isn’t it?

 

[BrendanC]

could always get some rotella 0w-40.

 

[0burb8]

Thank you for your thoughts. I'm planning to have the truck for a long time and keep it as good shape as possible so it comes with a certain cost, soo I decided that I'm going with 5w40 M1 Delvac anyway. That should be a no compromise solution.

 

[Snagglefoot]

An oil with a 10W winter rating is appropriate for starting down to about 0F or so. Below that and down to about -30 then use one with a 5W winter rating.

It would be foolish to use an oil with a 10W rating at -25. If you’re really worried about the HT/HS of the 30-grade at operating temperature then use a 5W-40.

Easy isn’t it?

Yeah, but getting it for free is part of this whole discussion.

 

[kschachn]

Yeah, but getting it for free is part of this whole discussion.

Sometimes thats a detriment not a bonus. It makes you think you need to use something when given the circumstances may not be appropriate.

 

[Urshurak776]

Use the 5w30. Shouldn't be an issue in Winter.

 

[twX]

Both grades have the same minimum HTHS requirement of 3.5 cP. The 5w30 will still be slightly thinner, but lower oil temperatures in the winter should more than make up the difference. The difference is only going to be equivalent to a few degrees of oil temperature.

That said, if you're using a block heater, the oil's cranking viscosity will be irrelevant. Its pumping viscosity (MRV) could still be relevant, since the oil in the pan won't heat up very much, but 10W oils have their MRV tested at -30°C. It would only potentially be an issue if there's a lot thickening from soot and oxidation on a long OCI. Since you've got access to free oil, I'm guessing that won't be an issue. You could always install an oil pan heater if you're concerned about it.

Either grade would be fine for winter, but I'd use the 5w30.

 

[Snagglefoot]

From a practical standpoint I have friends who run the Duramax using 10w40 and they are not reluctant to start it at -25 C, but generally they will plug in the block heater at -20 C if they remember. It really doesn’t matter that the block heater heats the coolant. You’ll be surprised how easily it starts with a warm block. 10w40 for the win.

 

[0burb8]

From a practical standpoint I have friends who run the Duramax using 10w40 and they are not reluctant to start it at -25 C, but generally they will plug in the block heater at -20 C if they remember. It really doesn’t matter that the block heater heats the coolant. You’ll be surprised how easily it starts with a warm block. 10w40 for the win.

Well this is what I also thought, I doubt that nobody has blown their Duramax by using 10w40 in the winter. I just often overthink stuff.

 

[kschachn]

Never mind. Perhaps people just want to do what they think is fine.

 

[Slick]

I'm about to do an oil change soon on my 2003 Silverado LB7 diesel. It gets occasionally down to -25°c where I live.

I can't decide what to do. I have free access to 5w30 and 10w40 Motul Tekma+ oils. Using 5w30, cold start lubrication is not a problem, but the viscosity is thinner at operating temp.
Using 10w40, cold start lubrication could be a problem, but the viscosity is what the engine calls at operating temp.
It's a small sacrifice both ways.

Please help and point me in the right direction.

Is the 10W-40 you can get for free a HDEO with a API CK-4 Rating?

If the free 10W-40 oil is API CK-4 rating, I would use that year round based on your temperatures from my experience. If the free oil is not a HDEO with API CK-4 rating I would not use it.

The 2003 LB7 Engine was designed to use a HDEO with API CI-4 (current rating CK-4). Factory fill for the 6.6 Duramax Engine since 2001 Model Year has always been 15W-40 with the most current API C?-4 rating)
For cold operation below -18C(0F) 5W-40 is recommended.

I have made many cold starts with the 6.6 Duramax down to -25C(-13F) without switching to the 5W-40 oil. My trucks were stored outside and did not have preheat or battery warmer blankets. Oil analysis never showed abnormal wear metals. Have made a few starts at -30C(-22F) with 15W-40 during the rare cold snaps we would have every 5 or so years. With good battery charge they would crank slow but still start.

PS. I would love free good oil. Enjoy.

Slick

 

[Shel_B]

I do have a heater. It heats the coolant. It has little to none effect on the oil, but sure it's better than nothing. Could go with 5w40 but I don't want to spend any money on oil when I can get it for free.
One thing that I thought of, is making a mix of those 2 oils I mentioned.

It's my understanding that when you do that, the winter, or cold rating, becomes an unknown.

 

[userfriendly]

2006 and older Duramax, LBZ and previous models showed an xW30 option in the owners manual.
LMLs and the 2017 and newer L5P engines show only 5W40 and 15W40.
If it makes you feel any better, I ran 0w30 for one winter in 2006-2007 in my daughter’s 06 LBZ when she was working in the gas fields in northern Alberta.
That truck is still running strong 18 years later. So imo, your free 5w30 will be fine and dandy.

 

[Blagoje]

I have been in colder temperatures when I worked for Roehl Transport and they put Rotella T6 15w40 in all their diesel engines year round. Never had any issues starting up.