Synthetic 15w-40 vs 5w-40

[SOHCman]

Exactly.
Not sure why CAFE was brought up in this thread. Neither grade is resource conserving.

CAFE was brought up earlier to make a point about thick vs thin protection. I believe it was due to the CAFE standards making OEMs look toward thinner as a solution to meet standards. This is of course possibly at the expense of protection depending on the engine we are talking about and how much the design shears oil.

 

[ruSSrt]

It's 5.9 cummins! Put some 15W-40 and forget it. I've used Delvac Super 1300 15W-40 for over 100k with changes every 5k. I maybe get two oil changes a year and I never had any oil related issues. Purrs the same as the day I got it.

 

[4WD]

It's 5.9 cummins! Put some 15W-40 and forget it. I've used Delvac Super 1300 15W-40 for over 100k with changes every 5k. I maybe get two oil changes a year and I never had any oil related issues. Purrs the same as the day I got it.

FF in DMax ….?

 

[BigJohn]

5W-40 all things equal is inferior to a 15W-40 due to the thinner base oil blend and the viscosity improvers needed. That being said and as mentioned the 5W wil lbe better below 0*f for cold pumpability. I use 5W-40 in my tractor because I change oil once a year and I want the cold pumping in the winter if there is a cold spell and the temps drop well below freezing and I need to clear the road or something..

I agree 100%.

I know that T6 5w40 has a HUGE following, but it has not performed well in my motorcycles and more recently in my EcoDiesel. Yep, I think this issue is the viscosity improvers and the oil shearing in certain engines and driving conditions.

I have two oils that I am tossing around for my next fill.....

Rotella T5 10w30 (Semi-Synthetic)
Rotella T6 15w40 (Full-Synthetic)

But I think I am done with 5w40 oils.


.............

 

[SteveG4]

I agree 100%.

I know that T6 5w40 has a HUGE following, but it has not performed well in my motorcycles and more recently in my EcoDiesel. Yep, I think this issue is the viscosity improvers and the oil shearing in certain engines and driving conditions.

I have two oils that I am tossing around for my next fill.....

Rotella T5 10w30 (Semi-Synthetic)
Rotella T6 15w40 (Full-Synthetic)

But I think I am done with 5w40 oils.


.............

You could be right. In comparison, let us know how the T5 10W-30 and T6 15W-40 oils work for you.

 

[xgmad]

HTHS is different, 15w40 index is better than 5w40, 15w40 is less reliant on viscosity index improvers.
15w40's also have much higher content in calcium, phosphor, zinc, and so fourth.

 

[benjy]

i have read many times of motorcyclists trying a 5-40 only to quickly DUMP it when shifting gets poor, especially with shared oil supplies. unlike redlines 15-40 that acts like a 10W when cold according to specs wide viscosity spreads dont do well. interesting link about thinner-thicker oils, a nice read enforcing my love for thicker oils!!

 

[OVERKILL]

HTHS is different, 15w40 index is better than 5w40, 15w40 is less reliant on viscosity index improvers.
15w40's also have much higher content in calcium, phosphor, zinc, and so fourth.

That may not be true. For example, as I posted previously, Mobil shows using Group II+ to blend an HDEO 10w-30 (similar spread to 15w-40), additives are 20%

Here's a 0w-40, 5w-40 and 10w-40, same 20% additive content in the 5w-40 as the 15w-40:

Heavier one in this table, 20.7%, 8.7% being VII:

Compare to a Group III 5w-40 where VII load is 11.8% for the "balanced" formula:

Another HDEO, this 10w-40 has 9.8% VII using Group II+, more than our 5w-40 Synthetic above:

I'll see if I can dig up one that specifically covers a 15w-40.

 

[4WD]

That may not be true. For example, as I posted previously, Mobil shows using Group II+ to blend an HDEO 10w-30 (similar spread to 15w-40), additives are 20%View attachment 78931

Here's a 0w-40, 5w-40 and 10w-40, same 20% additive content in the 5w-40 as the 15w-40:
View attachment 78932

Heavier one in this table, 20.7%, 8.7% being VII:
View attachment 78934

Compare to a Group III 5w-40 where VII load is 11.8% for the "balanced" formula:
View attachment 78937

Another HDEO, this 10w-40 has 9.8% VII using Group II+, more than our 5w-40 Synthetic above:
View attachment 78939

I'll see if I can dig up one that specifically covers a 15w-40.

I commented a while back that 10W40 would be a good HDEO spread for N America

 

[OVERKILL]

OK, here's a 15w-40, you can see that your typical Group II variant is ~20% VM+DI, similar to the 10w-30 I showed earlier, and the 5w-40 synthetic:

 

[OVERKILL]

And yet another data point, a 4-stroke ATV/UTV/Bike 5w-40:

10% VII; 18% VII+DI package.