Rethinking 5w-40 vs 15w-40 for my low use diesels

Status
Not open for further replies.

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,505
Location
New Jersey
No problem as long as the pressure gauge reads at least 1 bar at idle and is pegged before the engine reaches 1500 rpm. Do you notice a difference between different oils usually?
That’s all within spec and good. But I’m still used to seeing a pegged needle at cold start until the oil all truly heats up.

TBH my OCIs are seldom, and sometimes go long durations. I’m just used to seeing a cold start pegged, even when running 5w-40.

But the pressure in use is perfectly fine, and the engine runs smooth and well.
 
Joined
Jun 12, 2020
Messages
1,137
Location
SW Missouri
Joined
Aug 22, 2019
Messages
1,005
Location
AR
15W-40 all day long unless under 10°F - then I would look at engine heaters for sure....but I'd still use 15W-40
 
Joined
Dec 12, 2006
Messages
142
Location
Texas
Ford (and International) recommend 20 degrees to be the lower limit for 15W40 in the literature for the 6.0L diesel.

There are some indications that the filter is bypassed on startup if the cold oil is too thick (20 psi differential). Most of the time this isn't a big issue, but sometimes contaminants get past the filter and screen and get to the IPR valve.

I think that there is a benefit to following the low temperature limits stated by the engine manufacturer.
 
Joined
Oct 23, 2005
Messages
7,998
they don’t see conditions that are challenging, and the oil will get changed on calendar time over miles or running hours for the most part.

15w-40 is proven and the chances of very cold starts are nil.
You answered your own question there.
 
Joined
Oct 23, 2005
Messages
7,998
You answered your own question there.
Doesnt mean that 5w40 isnt still the better choice since some of the starts can be after a very long sitting period...
Jury's out on that one. Nobody agrees. 15w sticks better. 5w pumps faster. 🤷

But really, they're both thick as honey at start up anyway. And the higher the temperature when starting, the closer they are in thickness…

But since you are concerned with saving money, they are started very infrequently, and only in not really cold weather, IMO it does not really matter which one you use.
 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,505
Location
New Jersey
Jury's out on that one. Nobody agrees. 15w sticks better. 5w pumps faster. 🤷

But really, they're both thick as honey at start up anyway. And the higher the temperature when starting, the closer they are in thickness…

But since you are concerned with saving money, they are started very infrequently, and only in not really cold weather, IMO it does not really matter which one you use.
Im only mildly interested in saving money. The cost of 5w- vs 15w- isn’t enough to make a difference. It’s just an interesting angle.

agree the warmer it is the less it matters. It’s really the situation that 5w pumps faster, for a vehicle that has sat for a long time, that is the consideration of value…
 
Joined
Apr 12, 2009
Messages
68
I prefer 15w-40. Used to use Super 1300 as it has a quality base stock for a conventional. But now switched to the newer Delvac Extreme 15w-40 synthetic due to it having considerably more aw additives.

Super 1300 is now dual rated (SN) under CK4, so its additives are capped now, not ideal for a HDEO.
 

4WD

$50 site donor 2023
Joined
Sep 21, 2010
Messages
20,770
Location
Texas via IAH
Im only mildly interested in saving money. The cost of 5w- vs 15w- isn’t enough to make a difference. It’s just an interesting angle.

agree the warmer it is the less it matters. It’s really the situation that 5w pumps faster, for a vehicle that has sat for a long time, that is the consideration of value…
 
Joined
Apr 12, 2013
Messages
80
Location
44'N/88.5'W
I believe you're all over thinking all of this. If the OP's vehicles are sitting static for more than 30days and the engine was shut down hot, any oil will already have departed the wear surfaces. There is no "sticking" after a certain time. Only thing he needs to be concerned with is start up. Go with the lower viscosity 5w.
 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,505
Location
New Jersey
I believe you're all over thinking all of this. If the OP's vehicles are sitting static for more than 30days and the engine was shut down hot, any oil will already have departed the wear surfaces. There is no "sticking" after a certain time. Only thing he needs to be concerned with is start up. Go with the lower viscosity 5w.
But… what was going to depart surfaces hot would do so at the same rate regardless of 5w or 15w, since they’re both 40wt when hot.

The 15wt would have more strength at the next cold start… whatever was left. FWIW.

Oil pressure evokes up within a second. Hard to tell if 5w would come up in a half second vs one, or whatever else.
 

JHZR2

Staff member
Thread starter
Joined
Dec 14, 2002
Messages
49,505
Location
New Jersey
Nothing's going to "stick better" after 30 days regardless of weight. It's going to be a dry start whether it sits 30 days or 30 months for all practical purposes. If you're that concerned add something like Schaeffers Moly EP https://www.schaefferoil.com/documents/37-132-td.pdf which will "plate" the surfaces even when dry you'll have some sort of barrier from metal on metal.
Have you even tried moly EP? I have used it for decades now. It doesn’t “plate” anything. It actually thickens oil up, thereby going against what you said.

Never have I seen engines “dry” in locations. This is about flow to get journals to lift and cams to have more oil on them. Pulling VCs after months, there still is a film of oil on them...
 
Joined
Apr 12, 2013
Messages
80
Location
44'N/88.5'W
Have you even tried moly EP? I have used it for decades now. It doesn’t “plate” anything. It actually thickens oil up, thereby going against what you said.
They say it does but what do they know....yes I've used it in several applications for many years. It's not adding THAT much viscosity to a large sump. And "dry" is relative to normal everyday use...

"To complement this highly specialized additive package two proven frictional modifiers, Micron Moly®, a liquid soluble type of Moly and Schaeffer Mfg’s own proprietary additive Penetro. These two proven frictional modifiers once plated form a long lasting slippery tenacious lubricant film, which prevents the metal surfaces from coming into contact with each other."
 
Last edited:
Status
Not open for further replies.
Top