Oil weights

[ib516]

Ok, so doing some reading on these forums, there seems to be a few guys that are using a 5w30 or 10w30 HDEO where the engine manufacturer calls for a 15w40 or a 5w40.

The question I am left with is why? I don't understand why anyone would want to run a 10w30 in the heat of summer when the engineers that designed the engine say to use a 40 weight. Yes, I understand that the second number refers to the 100*C viscosity etc. I just want someone to explain the perceived advantage to using a lighter oil, especially when towing in summer.

I don't mean for this to sound like a "challenge", I'm just curious.

 

[Brons2]

Some have gotten better oil analysis results with 10w30. There's one guy on here who's using John Deere Plus 50 10w30 with excellent results.

 

[dave1251]

Often the 40 viscosity oils will shear down to a 30 viscosity and at operating temps 10w30 and 5/15W-40 are almost at the same viscosity.

 

[bepperb]

More power, greater fuel economy. Since most engine wear occurs at startup and an oil with lower KV flows more quickly then it can result in a decrease in wear.

Really, you only need an oil heavy enough for the maximum requirements for the engine and application. Heavier than that is not "better".

Also, you seem to be asking a very specific question in a very general way.

 

[ARCOgraphite]

Most engine wear has been proven to occur under load. BUT If you only drive 4 miles or less to work then its probably at startup warmup

 

[Oil Changer]

Learn to say "grade" not "weight".

I for one would use "40" if my application called for "40". However, it would be "5" or "0" preceeding the "W".

That's a personal opinion. Other than that, your question has been answered.

 

[dnewton3]

I am one of the guys that does it. I'm not taking this as a "challenge" as you put it; it's a fair question. No affront is taken; let's consider it a pleasant debate rather than adversarial.

GM allows for 15w40, 5w-40 and 10w30 for my Dmax. The "preferred" oil is 15w40. The others are "approved". So, I'm not really venturing off the reservation, I'm just one of the few that venture outside the "norm". Same can be said for my GoldWing (10w-30 or 10w-40), my Kubota (10w-30, 10w-40, straight 30), etc. I use the 10w30 HDEO in my Kubota, GoldWing, Dmax, 1966 Mustang 289, and various air-cooled small power and lawn equipment. Some of thos spec 10w30 as preferred, some do not. But they all allow for the use of 10w30.


Several reasons to do so (in no particular order)
* fuel economy and power
* cold cranking and pumpability during critical pressurization period
* one OCI per year as opposed to two with a "winter/summer" multi-fluid plan
* to be "different"
* to show that fear of thinner fluids is very often unwarranted
* commonzation of fluids across a fleet
etc

Rotella TP 10w30 fits my needs across a wide range of my vehicles (not all, but many). It performs admirably. My used oil analysis show it's not been even the least detrimental in wear protection versus using 15w40. I absolutely flogged my Dmax last year in the searing heat of UT and AZ pulling my travel trailer using conventional 10w30, and got fantastic UOA results.

And I'm not the only one that does it. Yes - those like me are in the minority, but it's a growing trend, a growing sub-market, if you will. And, 10w30 is becomming more widely accepted in the OEM market, too. I believe that Ford spec's 10w30 for the new 6.7PSD, do they not? The "preferred" oil is 10w30, and yet they also approve 5w-40 and 15w40. Kind of opposite of your question, as it were.

In summation: I am assured of excellent wear protection, lower costs, and reduced shelf inventory. Those are not "perceived" advantages; they are tangible. I can and have proven them to be valid and attainable. It's not a perception; it's a reality.

In light of the evidence, I'd have to ask you, rhetorically: Why not?

 

[Garak]

Originally Posted By: ib516
Ok, so doing some reading on these forums, there seems to be a few guys that are using a 5w30 or 10w30 HDEO where the engine manufacturer calls for a 15w40 or a 5w40.


In addition to the other answers posted so far, I think, perhaps, that automotive manufacturers have been a bit behind the curve with oil choices in their diesel trucks. Gas engines got hit with emissions controls first, and manufacturers found that gassers don't die premature deaths with lighter oils. Further, oils have gotten better. Back in the day, even gas engines specified heavier oils for various reasons, including fuel dilution.

So, I think we have a lot of legacy recommendations when it comes to HDEO. There's nothing wrong with 15w40, for sure, but it's certainly not the only grade that works. 15w40 has certainly been the standard grade for a long time. Heck, when people with diesels have asked me for a grade recommendation, my standard answer was "15w-40, what else would it use?"

 

[Jim Allen]

Well said, Garak!

 

[ib516]

I did see that Ford specs 10w30 for their new diesel, but don't they suggest 5w40 or 15w0 when used for heavy towing or in hotter weather? I'm not sure, but I think I read that somewhere.

On the wear at start up that was pointed out as a reason - well that's the opposite of what I would think. A 5w40 would be better at start up than a 10w30 right?

Maybe the fuel economy wins out once up to operating temp as the oil would/should be slightly "thinner" when up to temp being a 30 rather than a 40 SAE.

Is 10w30 oil cheaper?

I did look in my manual and turns out the Cummins can be fed 5w30 synthetic in arctic conditions.

Anyway, thanks to those who answered

 

[dnewton3]

Originally Posted By: ib516
On the wear at start up that was pointed out as a reason - well that's the opposite of what I would think. A 5w40 would be better at start up than a 10w30 right?


As a massive generalization, yes. But that is such a broad sweep of the pen that it's hard not to find exceptions.

Examples: Rotella T5 10w30 semi-syn and T6 5w-40 Full Synthetic have essentially the same cold crank rating. A 10w semi on par with a 5w syn.

As I recall, some of the Mystic semi-syn and Full Synthetic oils have some really impressive MRV specs too.

As often said around here; YMMV.

 

[rufushusky]

IMHO long term, I would expect the diesel industry to be moving towards 10w30 oils, for simple fact oil technology has improved over the years and very viscous oils aren't required anymore for good protection. Fuel economy is king now with diesel prices fluxing all over the place, so OEMs will turn over every stone they can think of to pick up some efficiency...much in the way the "standard" PCMO has started to move from a 10w30 to a 5w-20 with respect to FoMoCo.

Personally, I haven't seen any change in MPG with T5 10w30 but cold starts, even with a busted GPR, have been as good as a 5w-40 IMHO. In the spring, summer and fall, as one would suspect, the advantage isn't there and since economical 10w30s haven't made their way to SE Mass...I will continue to use conventional 15w40 during those time periods and the 10w30 in the winter. Which usually works out well for me, I am a three OCI a year guy anyways...usually cover 22-25k a year.

 

[A_Harman]

I would like to see diesel-rated 5w30 synthetics become more popular in the near future. If they can be formulated with HTHS of around 3.8, I think they would run fine in most diesels.

 

[Ken2]

The viscosity of the oil relates to the film strength of the oil in the bearing. The needed film strength relates to the psi load on the bearing parts. If the bearings are made bigger, they can handle the load with lighter viscosity oil for the benefits mentioned above. This is easy to do when an engine is redesigned, and some current designs have been tested and found suitable for the lighter oils.

Much harder to do is to change public opinion. Getting someone who's had good results with 40 wt to trust 30 wt in an expensive engine that might be his livelihood is tough.

Very large diesel engines, up to 100,000 hp on 14 cylinders, use 30 wt. crankcase oil. They'll run many, many years, 24 hours a day, sometimes for a month then a break of a day or two, then run again, without a bearing change. These engines have the combustion space sealed from the crankcase and use a 50 wt, 70 TBN oil pumped through the cylinder liners to lube the piston skirts and liners--they burn heavy black fuel oil up to 3.5% sulfur.

 

[JR]

i had 95 ford f-heavy duty 4x4 7.3l psd, had 317k on the clock when my cousin bought it from his company, was his company truck. his company had a 6to7.5K oci's using 30wt, he continued with the same. i bought it with 478k, had no problems for two years except 6months after i got it the odometer stopped working at 523k, drove it another year and a half. I sold it to a friend back in 2007. he put injectors and head gaskets six months ago and each cylinder passed compression over factory spec and all balanced in a 25psi window, still could see crosshax like it was just bored. still going on 30wt year around