5w-40 vs. 15w-40 the real truth?

[mbacfp]

Hello all,

Got a 2014 ford F550 6.7 powerstroke. Been running 5w-40 synthetic (Valvoline and DELVAC). The Ford manual says for severe service run 5w-40. I wanted to get some opinions on 5w-40 vs. 15w-40? Keep in mind I am not looking to extend drain intervals...been changing every 5,000-6,000 miles or one year. It is a 35 foot Class C motorhome so it is always under load and going at highway speeds.

Question, does the 5w-40 lubricate, clean, and protect better than conventional 15w-40? Does the 5w-40 have better detergents, etc. than 15w-40? Or is the main difference the quality of base oils in the 5w-40 makes them last longer than 15w-40? Fresh oil (5w-40) vs. fresh oil (15w-40), is one better than the other at protecting the engine?

Thanks a lot.
Thanks.

 

[JHZR2]

Ill start with the typical entry statement: Only you know your driving style, load and use profile, and expected conditions and obtained MPGs, so the best insight is a few back to back UOAs.


That said, Chevron did a study a few years back comparing the only readily available 5w-40 syn on the market (this was a number of years back, and it was Delvac 1) against their ISOSYN 15w-40 in fleet use. Given the typically fully warmed up operation, there was negligible improvement or benefit to running the syn vs the premium conventional. At your OCIs, Id suspect that the economics aren't there for the drain interval factor...

Of course they were trying to sell their premium conventional ISOSYN 15w-40, so take it with at least a fraction of a grain of salt... Which is why I opened this post how I did...

Edit:

Originally Posted By: JHZR2
Delo 400 is on par with delvac 1 per an SAE paper entitled "Lubricants that Optimize Diesel Engine Fuel Economy and Allow Extended Oil Drains", presented to the SAE at the International Spring Fuels and Lubricants Meeting and Expo, May 7-9 2001.

SAE 2001-01-1968

According to Chevron, it still holds...


And here's another old good one:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2440256&page=all

 

[bubbatime]

That's what, a $100K or more motorhome, and you are trying to save $8 on an oil change? Ok...

 

[CarbonSteel]

Originally Posted By: bubbatime
That's what, a $100K or more motorhome, and you are trying to save $8 on an oil change? Ok...
Likely closer to $40 per OC (but I understand your point).

 

[IndyIan]

From what I can find, the HTHS numbers are pretty close between Rotella T6 and 15W40, but if Ford says to run 5W40 and you do have to climb some significant hills, then I'd get the synthetic and not worry about it.

 

[Solarent]

Question, does the 5w-40 lubricate, clean, and protect better than conventional 15w-40?
Hypothetically yes, but not necessarily - how's that for a confusing answer

...The reason I say this is because base oil selection to get 5W40 requires higher quality base stocks (generally synthetic) robust VII (25 SSI) and I would says is typically more robust (as 15W40 can be made with just about any base oil) If you are using both from the same brand, you can probably expect similar performance (as above with the comparison between DELO and DELVAC)

Does the 5w-40 have better detergents, etc. than 15w-40?
Not typically. Although the ratios of detergents/dispersants may be different than the additive packages of the two products. This is related to the base oil selection - although both will be held to the same minimum standard of deposit and soot control (API CJ-4)

Or is the main difference the quality of base oils in the 5w-40 makes them last longer than 15w-40? This is one of the main differences, but as above when a base oil mix is changed sometimes this necessitates changes to the additive package as well.

Fresh oil (5w-40) vs. fresh oil (15w-40), is one better than the other at protecting the engine?

In your application I would probably stick with 5W40 - a personal preference to using synthetics when going with annual drain intervals - although honestly you could probably use either.

Thanks a lot. You are welcome.
Thanks. Again... you are welcome.

 

[roadrunner1]

Is 10w-30 even recommended in your application? I would think that it would hold up just fine, as I have a 6.7 also. The only real difference would be yours is turning higher rpm's due to gearing (I have 3.31)

 

[bullwinkle]

If you're always starting it in temps above freezing (you're in Cali after all), I can't see the savings. And I'm a guy who uses 5W40 in my Ram all the time (helps it start below 0F).

 

[mbacfp]

I really do appreciate all your advice and wisdom. Lots of stuff I read about synthetic (5w-40) vs. conventional (15w-40 or 10w-30) leads me to believe a synthetic oils' strength lies in its extended OCI and is more durable under extreme driving conditions (heat and cold). So, I have been following Fords 5w-40 recommendation but have run across some stuff on this site (from DNewton...I think) that running even 10w-30 while towing would be fine.

I guess my overall question is does 5w-40, 10w-30, and 15w-40 all protect an engine equally (lubrication, detergents, etc.) from the get go and the difference is strictly how long the oil TBN holds up after various OCIs? I don't want to come off as a penny pincher, just curious how it really works. For warranty purposes, I should probably stick with 5w-40.

Thanks again for all the input.

 

[CT8]

5w-40 better below 15*f starting. 5w-40 probably has a higher amount of viscosity improvers. In real life other than starting below freezing there is no real difference. Make a choice and you probable will never see and difference except at extremes. 5w-40 will cover all bases with out doubt from below freezing to above 100*f

 

[mbacfp]

Ok...that makes sense. Thanks.

 

[JR]

The only real world difference will be cold weather starting. Early heui systems use Hi pressure lube oil to opens the injector. Later system use oil to both open and close the injectors.
And maybe extended oci's using uoa tests. And that's a big maybe. These engine hold gallons and ford says 5,000 tops on oci's.



Harvey.

 

[roadrunner1]

The engine the OP has is the 6.7 and doesnt employ the HEUI system, its common rail. Also this engine family has an IOLM and from my experience with it its very conservative.

 

[mbacfp]

I called a large Ford Fleet service center in Van Nuys, CA and asked them what oil they use for fleet F550s (severe service) and they told me 10w-30. Perhaps the 6.7 powerstroke isn't as hard on the oil as the 6.0 like roadrunner1 points out? Not sure why the dealers don't follow Ford's recommendations?

 

[Garak]

Has there been a bulletin from Ford that perhaps we don't know about, or that some of us here might know about? Given your OCIs, and the cost involved, I'd be tempted to stick with the conventional over the synthetic.

 

[mbacfp]

That is why I was curious if 15w-40 or 10W-30 will equally protect (fresh oil to fresh oil) equally to 5w-40 synthetic? Since I don’t plan on extending OCIs due to time, fuel dilution issues (regens), etc...I guess there is no answer on them equally protecting fresh oil to fresh oil (understand temperature spectrum circumstances)? However, if synthetic did provide superior lubrication properties above and beyond conventional other than extended OCIs, then I can see it being a better investment for your engine.

 

[Garak]

I can't see the 5w-40 providing a lot of benefits over the 15w-40, given your OCIs and your climate. But, it is interesting that the 10w-30 was being used by them as the service fill. I can't see it being much of an issue, but it's been historically the go-to solution to choose 15w-40 for a diesel, whenever there's the slightest doubt.

 

[mbacfp]

I believe you are correct. I think the movement to 10w-30 is for fuel economy economics as another member posted a link to the chevron study attempting to show no loss in engine protection with 10w30 vs. 15w40. Truthfully, the main reason I am using 5w40 is to maximize the turbo charger longevity...so I thought. I will stick with 5w40 as I got 2 oil changes with delvac esp 5w40. Perhaps there is some truth to it...just needs to be tested more.

 

[Gokhan]

Originally Posted By: mbacfp
Hello all,

Got a 2014 ford F550 6.7 powerstroke. Been running 5w-40 synthetic (Valvoline and DELVAC). The Ford manual says for severe service run 5w-40. I wanted to get some opinions on 5w-40 vs. 15w-40? Keep in mind I am not looking to extend drain intervals...been changing every 5,000-6,000 miles or one year. It is a 35 foot Class C motorhome so it is always under load and going at highway speeds.

Question, does the 5w-40 lubricate, clean, and protect better than conventional 15w-40? Does the 5w-40 have better detergents, etc. than 15w-40? Or is the main difference the quality of base oils in the 5w-40 makes them last longer than 15w-40? Fresh oil (5w-40) vs. fresh oil (15w-40), is one better than the other at protecting the engine?

Thanks a lot.
Thanks.

5W-40 = thinner oil, more wear, better fuel economy, longer (synthetic) OCI
15W-40 = thicker oil, less wear, worse fuel economy, shorter (conventional) OCI

Reference: John Rosenbaum, Chevron (link)

"The Ford manual says for severe service run 5w-40."
Translation: To maintain the same OCI for severe service, use a synthetic oil. Alternatively, for severe service, decrease the OCI if using conventional oil.

My take: If your truck doesn't show significantly increased wear with 5W-40 (thinner oil), use 5W-40 for cleaner engine and longer OCI, as it's synthetic. Yes, the difference between conventional and synthetic is only the base oil. Rotella T6 5W-40 CJ-4 is very popular. There is also Mobil 1 TDT 5W-40 CJ-4. I usually prefer ExxonMobil over Shell. My favorite conventional is Mobil Delvac 1300 Super 15W-40 CJ-4 -- it's probably the best-overall conventional 15W-40.

The following analysis from PQIA shows that Rotella T6 is a rather low-grade Group III synthetic because its NOACK barely meets the CJ-4 minimum. Mobil Delvac 1300 Super 15W-40 has a much lover NOACK -- of course, it has a much thicker base oil, too, so much easier for it to be less volatile. For a given CCS, NOACK is an indication of base-oil quality ("syntheticness").

http://www.pqiamerica.com/June 2014/consolidated HDEO 2015.html

 

[CarbonSteel]

Originally Posted By: Gokhan
5W-40 = thinner oil, more wear, better fuel economy, longer (synthetic) OCI
15W-40 = thicker oil, less wear, worse fuel economy, shorter (conventional) OCI


So how much thinner is 5W-40 versus 15W-40 (honest question)? It is 1.1KV difference so what does that equate to? I am not sure that I agree that a 5W-40 will cause more wear than a 15W-40--why do you think this?

Delo 5W-40

Delo 15W-40