Max temp for SAE 30 in a diesel

[JHZR2]

Hi,

Im changing over to rotella in my 82 MB diesel, and so picked up some sae 30 rotella because it is cheaper and I wanted to try a single grade lube.

My temp/viscosity chart looks like this:

So you can see the range for sae 30, and also when running 40 is applicable. FYI summertime startup temp viscosities are as follows:

Rotella 15w-40 is 120 cst at 40C
Rotella SAE 30 and 40 are 107 and 120 respectively.
Rotella 5w-40 is 87.

So while a 5w-40 will pump a bit faster, the others will all flow roughly the same at startup in a heat wave, it seems to me.

But since the sae30 is rated up indefinitely in the chart shown, and sae40 has been blessed for use over 30C, is there a practical temperature limit beyond 30C to run sae30, and beyond which 40wt really is the lube of choice?

Any insight would be appreciated.

Thanks!

 

[Doug Hillary]

Hi,
JHZR2 - I found your question a little confusing so opted for a reply based on maximum operating ambient temps. Typically as MB build a "margin for error" in their recmmendations and IMO SAE30 monograde will by OK up to a continuous ambient around 40C and beyond that a SAE40 would be prefereable

I have run SAE30 in some HD engines in such ambients without and dramas

 

[Chris142]

Your underpowered MB Diesel won't work the oil enough to matter.

 

[eljefino]

You have a pressure gauge, tell us.

I had slightly over 2 Bar in my 240D at slowest hot idle on 15w40. More than plenty. Otherwise it was always pegged at 3.

 

[JHZR2]

Originally Posted By: eljefino
You have a pressure gauge, tell us.

I had slightly over 2 Bar in my 240D at slowest hot idle on 15w40. More than plenty. Otherwise it was always pegged at 3.


The FSM lets pressure go as low as 0.7 bar... Not what I'd call optimal...

I can play trial and error, but don't really care to come out on the wrong side of the oil pressure scenario when on a trip. I have hundreds of thousands of miles experience in these cars running 5w and 15w-40 oils, thus is my first attempt possibly with a 30wt.

 

[JHZR2]

Originally Posted By: Doug Hillary
Hi,
JHZR2 - I found your question a little confusing so opted for a reply based on maximum operating ambient temps. Typically as MB build a "margin for error" in their recmmendations and IMO SAE30 monograde will by OK up to a continuous ambient around 40C and beyond that a SAE40 would be prefereable

I have run SAE30 in some HD engines in such ambients without and dramas


Doug, what I was going after is that the temp/visc chart implies that sae 30 is good to as high an ambient temperature as I desire. The arrow pointing up off its line to me means it is ok for use from over 86 to whenever.

Bur my query was really just asking when are the temperatures sufficiently high to justify running sae40 instead, because 30 may prove to just not be viscous enough? Mb says 40 may be used over 86F... At what ambient temp would it be prudent to change that "may" to a "must"?

My guess is that they limit the 40 recommendation based upon cold start flow characteristics... The 30 flows a bit better, it can thus be used in a bit wider scenario set.

But since 40-50wt oils are generally what is recommended, I'd imagine it is either because they are nultigrades, which mb is worried would shear down, or because at higher temperatures, sae 30 just is not viscous enough to properly protect. If that is the case, at what conditions is it really a consideration?

Thanks!

 

[roadrunner1]

The biggest problem here is the use of a 30 year old owners manual. multi-grade viscosity oil was frowned upon until the 90's in diesel applications. I know in my own situation of many different diesel and industrial gas engines in use we used 30wt up until the late 90's in everything except the one 6v92 which required 40wt. We then made the switch to 15w-40, what a difference in cold starts. Now almost everything is being run on 10w-30.

The detroit is long gone and the two big Deeres and the couple of Dodge Cummins require 15w-40, but everything else is seeing a year around diet of 10w-30. To the OP, if you don't feel confortable with 30wt. then switch to a 15w-40, either way you'll be fine.

 

[Oldwolf]

This not what you want to hear maybe, but I would just run 15W40 in your MB if it were mine... and that is what I run in mine.

 

[2cool]

I was stationed at Ft. Bliss, TX. Cheek by jowl with ElPaso. High (4,000 ft) desert. All we ever ran in the Army trucks (140hp ish multi-fuel diesels) was OE30 (Oil Engine). Daytime temps in the desert in July would be around 110F, and they kept on trucking.
My $.02 is to use 30 up to ambient temps of 90-100F. If you are loaded to the max, and you'll do some grades; think about the 40.
Have you explored putting a boost cooler on it? IRIC, those old 300D and TD didn't have aftercoolers.

 

[Steve S]

The straight 30 lower temps are at just above freezing to over 100*f . The company I worked for had 4 branches 1 in South San Francisco Ca. the main branch in San Jose Ca. a branch in Salinas Ca. and 1 in Dublin Ca. Mild winter temps rarley ever are freezing and up to 100* at times. I used to travel from South San Jose to above Clear Lake Calif which is above the Napa Valley I would sometimes drive 1,500 miles a week on occasion fixing new equipment warranty, other mechanics screwups or on things the others couldn't do by themselves and I could. Anyway the company used Delo 400 straight 30 most of the time and rarely Nissan or Clark branded oil which was a HDEO by Ashland oil and may have been a 10w-30. In all the company cars Ford vans and their 3 class 8 vehicles all the equipment they service and the forklifts they rented and leased. They never had engine failures in the 17.5 years I worked there. I will say if the temps are right for the oil the oil will be fine try it with out worry. Let the engine warm up a bit before wot as with all oils.

 

[JHZR2]

Originally Posted By: Oldwolf
This not what you want to hear maybe, but I would just run 15W40 in your MB if it were mine... and that is what I run in mine.


I actually run 5w-40. Im mainly going to run this as a flush changing brands to rotella (Im anal like that), for a short run, and SAE30 is cheaper than the 15w-40 so I figured id try it so that I can say that I've run a straight weight oil. In this heat wave, the SAE 30 will actually be less viscous at ambient startup temps than the 15w-40! The car does have an OE oil to air cooler, BTW, and about 8.5qt of sump capacity (7.5qts gets changed in an oil and filter swap).

So this is in many ways more theory than anything else. I just figure that MB gives the option above a certain temperature because SAE 30 becomes a bit too thin for their comfort at SOME temperature... but doesnt say. And the way they state it, its not like a warning or anything.

Being able to run 30wt oils would be an interesting thing to see if I can get an extra MPG out! But I only want to do it under mandated conditions per the chart shown...

Thanks!

 

[BobFout]

Originally Posted By: JHZR2
Originally Posted By: Oldwolf
This not what you want to hear maybe, but I would just run 15W40 in your MB if it were mine... and that is what I run in mine.


I actually run 5w-40. Im mainly going to run this as a flush changing brands to rotella (Im anal like that), for a short run, and SAE30 is cheaper than the 15w-40 so I figured id try it so that I can say that I've run a straight weight oil. In this heat wave, the SAE 30 will actually be less viscous at ambient startup temps than the 15w-40! The car does have an OE oil to air cooler, BTW, and about 8.5qt of sump capacity (7.5qts gets changed in an oil and filter swap).

So this is in many ways more theory than anything else. I just figure that MB gives the option above a certain temperature because SAE 30 becomes a bit too thin for their comfort at SOME temperature... but doesnt say. And the way they state it, its not like a warning or anything.

Being able to run 30wt oils would be an interesting thing to see if I can get an extra MPG out! But I only want to do it under mandated conditions per the chart shown...

Thanks!


I know it would be expensive, but Amsoil HDD 5w30, Redline 5w30, or a Euro 5w30 might get you that extra MPG. You'd be good all-season with those too.

 

[bullwinkle]

The biggest thing with my (and most) older MB diesels is getiing enough cranking speed to start cold-I actually run Delo 400 straight 30 in my '82 in summer, and 5W40 Valvoline PBX syn in winter, the 30 is just a little too thick for that engine, although the IDI 7.3 Ford & 6.2 GMC handle the 30 just fine in winter. I can't imagine working a passenger car MB 617 motor hard enough to need a straight 40! That stuff is usually Detroit 2-stroke territory!

 

[Jim Allen]

Well, it's an interesting experiment but I predict no noticeable drama. Do you intend to UOA and can you read oil temps? Knowing those two things would add a lot of spicy interest to the experiment.

I've forgotten most of what I knew from my days working on MBs in the late '70s and early '80s, and I knew next to nothing about oil then, but I do remember the dealer and private shops using mostly straight 30 grade and sometimes 40 grade. This was in central California, where it gets pretty hot in the summer but generally above freezing in winter.

Were not those engine rated for API CD (or thereabouts)? All of today's oils are way better than that. Even the straight grade 30 is CF. Frankly, I think you'd be better of with a more up-to-date CI4 or even CJ (when combined with ULSD).

Did you consider a 10W30 oil? They are almost as robust as the straight 30 and have more up-to-date additive packages... especially the T5 variety. A 10W30, IMO would give you some of the best of all worlds... shear stability, something close to the ideal "as thin as possible as thick as necessary" viscosity (IMO anyway). Covers you winter, summer as well as better "cool" flow.

I will second bullwinkle's concern over cold cranking.

I remember working on a regular customer's black 180D back then... and it gave me new meaning for the word "slow" but it had 300K miles on it and didn't look like it it was anywhere close to retirement. You pretty much had to row that thing through the gears (four-on-the-tree IIRC) and rev it like mad to get any action at all. I still remember the smell of that car. Diesel fuel combined with leather and a peculiar ambiance that only the materials used in older Germans car interiors had... horsehair perhaps.

 

[bullwinkle]

Horsehair! The first time I ever test-drove my '82 it was a warm summer afternoon-smelled EXACTLY like my first car ('64 VW Beetle)-of course minus the flapping rusty floorbosrds and running boards, and the lack of A/C and heat. The SAE 30 of today is far ahead of the CC/CD of the old days, the Delo I run is CH-4-and it's probably 6 year old stock now!

 

[JHZR2]

Originally Posted By: Jim Allen
Well, it's an interesting experiment but I predict no noticeable drama. Do you intend to UOA and can you read oil temps? Knowing those two things would add a lot of spicy interest to the experiment.



Me either. Just giving it a whirl. I dont think Ill have it in long enough before I change over to T6 for it to be worth a UOA. Ill have to see.

Quote:


Were not those engine rated for API CD (or thereabouts)? All of today's oils are way better than that. Even the straight grade 30 is CF. Frankly, I think you'd be better of with a more up-to-date CI4 or even CJ (when combined with ULSD).



I agree. But this is a combo of somthing to run for a short OCI, with it being the summertime, with the SAE 30 being cheaper (not that I care much about oil cost). This isnt a long-term decision, more a combo of trying something new with some question of theory.

Quote:


Did you consider a 10W30 oil? They are almost as robust as the straight 30 and have more up-to-date additive packages... especially the T5 variety. A 10W30, IMO would give you some of the best of all worlds... shear stability, something close to the ideal "as thin as possible as thick as necessary" viscosity (IMO anyway). Covers you winter, summer as well as better "cool" flow.



10W30 in CCMC G5 spec (which I believe is now ACEA A3) would be acceptable to 86F or beyond. Regular 10w-30 not carrying that spec are only good at very low temperatures per the chart (likely due to the low quality VIIs of the day).

Quote:

I will second bullwinkle's concern over cold cranking.



At summer ambient temperatures (30-40C), the cold cranking viscosity of a multigrade and a straight are about the same. In fact, at 40C, an SAE 30 will have a lover viscosity than a 15w-40!

 

[JHZR2]

Originally Posted By: Doug Hillary
Hi,
JHZR2 - I found your question a little confusing so opted for a reply based on maximum operating ambient temps. Typically as MB build a "margin for error" in their recmmendations and IMO SAE30 monograde will by OK up to a continuous ambient around 40C and beyond that a SAE40 would be prefereable

I have run SAE30 in some HD engines in such ambients without and dramas


Doug,

Your answer is good, but what Id like to know is why, from a theory basis, is it OK up to around 40C? What is the basis for that versus 50C? Is it steady-state operational engine oil temperature? Is it the thought that with 10C less delta-T, the oil will be a few degrees hotter and thus less viscous?

Or do you think that it is just more for convenience? I know my FIL who distributes chevron/texaco sells a LOT of URSA SAE 40 straight in the tropics. Might just be something that people have on hand?

 

[Doug Hillary]

Hi,
JHZR2 - As you know these engine are quite easy on their lubricant. This follows on from earlier history with small MB Diesel engines in cars - the most popular Cabs in Europe (still are)

In the end it is typically a mixture of consumption, convenience, availability and application. When these engines were conceived mono-grade lubricants were common and in most applications MB specced an SAE30 lubricant for all temps above 86F and 20W-20 down 13F and 10W below 13F. If oil consumption was an issue below those temps the advice was to use SAE30. No such advice applied to use an SAE40 viscosity at very high temps

Very few Countries have continuous ambients nearing 50C and here we have them around 40-45C in some locations. It is common to use 15W-40 all year round but I suspect this is a convenience issue rather than a need - I don't know of a road going diesel operator that uses a SAE40 lubricants - all road train operators (four trailers and Gross train weights up to 120tonnes and beyond) I know of use 15W-40

So yes, once the ambient is constant above say 40C then the extra viscosity of the SAE40 lubricant provides the "safety margin" as the engine reaches a higher coolant/oil temp equilibrium - the "steady-state" temperature you mention

For instance in earth moving equipment situations in very high ambient temperatures the high engine load factor is really not very constant so the commonality of the SAE30 viscosity is quite common. It is different in road going equipment - hills, long gradients, following winds etc etc. sometimes allow very high load factors for hours on end!

I was involved at MB in the development of the first high speed high output V8 diesel engines here. The "field" prototypes suffered many problems due to radiator size, fan output/speeds, coolant capacity, dipstick length variability/oil pan size and oil cooler size - all told around 20 odd factors IIRC. These were on 15W-40 lubricants - a SAE30 lubricant would not have survived very long at all!

This may not answer your question but I can attest to the fact that SAE30 monograde HDEOs from the majors are very robust lubricants. Your purchase should work well for you

 

[JHZR2]

Doug,

Thanks as always for such a great response!

Just one small thing... You mentioned that in the MB testing that it was done on 15w-40, and that 30 would have fared poorer... But why is this the case? I'd think that 30 would be less succeptible to shear...

Is it that a sheared, abused 15w-40 will still have a better film strength than an sae30? What if an sae40 had been used?

Thanks again for your insight!!!

 

[Doug Hillary]

Hi,
JHZR2 - Greater film strength of the 15W-40 (over SAE30) at the very high temps encountered - a SAE40 would probably have fared better

The engines involved had very high oil consumption too - as you can imagine