BMW wants 15w-40 or 50?

[JHZR2]

Hi,

My 91 BMW 318i uses minimal oil, runs great at 80K, and is speced to use 15w-40 or 50 oil above 5F or so. My question is why?
15 wt oil is pretty think below 32F, and I cant imagine it flows very well through the small 4cyl, or could crank very fast (this is my first year with this car, and I have Castrol Syntec (I got it cheap and didnt know as much then) 10w-40 in it), so why have the very high first number? WHat is the point, if it is quite thick at cold temperatures, and cant possibly protect as well.

My diesel specs 15w-40 for most of the time, just the same, and I use delvac1 in it during the winter, but only because a lot of people use the thin oil with no apparent problems. But I havent heard as much about the BMW oil selection, and it is a gas engine instead of diesel as well, if it makes any difference.

I now think that my best bet is to either use mobil1 15w-50 year round, or use a dino diesel oil (15w-40) during the warmer months and swap to the M1 during the winter. This is my around town car, so frequent changes are probably in order, but at the same time I want the flowability of synth in the cold (and not spend too much $$$).

Any info on why such a thick oil would be used in this engine, and info on what would happen if I used a thinner base weight oil in the warm months damage-wise would be appreciated. Also, I have read that current BMWs use 5wt oils in their NA market cars for fuel economy reasons, but use much heavier oil in their euro (same engine though) cars. I have read that people are apparently using the thicker oils that the cars are designed for, in order to have better protection. Does this idea translate to other brands of cars, or, say, a chevy truck engine? Would that, which is speced for 5w-30 be better protected, etc with a 15w-40 oil, or is this too much for the internals of the engine? Thanks
[ February 03, 2003, 11:38 PM: Message edited by: JHZR2 ]

 

[sprintman]

15W40 would not be regarded as a 'thick' oil here. New M3's spec a 5W60. The oil company rec viscosity for yor vehicle here is generally 15W40 or 5W50. The D1 is probably a good idea year round and has an excellent additive package. Why change?

 

[eldawg4100]

yea... i work at a dealership that sells BMW among many cars... they sell either 5-30 BMW synthetic (group III i bet) and for dino they say 20w50? i dont understand it really lol

 

[JHZR2]

Actually, while this thread is near the top, Id like a bit of help in choosing the oil I shall be using from now on. My two main choices are Mobil1 and Castrol GTX.
90% of my car's use is moderate speed, short trips. Most are between 3-7 miles, just enough to get the coolant up to full temperature, but not much else. Because of this I will be changing my oil on the 3 months, 3000 mi interval, regardless of type.
Becasue I do a lot of short trips, I want maximum protection at startup. Since my BMW calls for 15w-40 or 20w-50 oil, synth seems to be the winner here, in the mobil1 15w-50 variety. Because its a synthetic, I imagine it woul dbe pretty good in the cold as well (it gets to 0F at the coldest, and that is rare).
However, castrol GTX is a good oil, and since I dont care to extend drain intervals, due to the nature of the car's use, I was thinking of this scenario: use 20w-50 in the summer, and mix in 50/50 of 5w-30 and 20W-50 in the colder months. How does this sound? WOuld it be better to mix 50/50 of 10w-30 and 20w-50, to keep the first number high (dino oils iin the cold can thicken pretty much though).

It seems that the M1 is the best year round, single grade choice, but the castrol wins at the price point... But I worry about winter startup, as I dont want to use a straight 5w30 oil, as the high number isnt high enough for the requested specs, and I dont want to use a 20w-50 oil, as its too thick in the winter. At the same time, my truck uses 5w-30 oil, so having that and the 20w-50 for the BMW isnt a problem (as opposed to also stocking a case of 10w-40 oil for winter use), as opposed to having to keep a case of all three varieties.

 

[OneQuartLow]

JHZR2, As for why the high first number, it's to try for a lower viscosity spread. You've probably encountered people warning against 10W40? As a generalization, the wider the spread the more VII's and the greater an oil's tendency to burn/sludge/thicken/change under stress. Better oils resist this effect. The manufacturer doesn't want to recommend a huge spread for fear you'll buy a marginal oil with wonderful specs but bad performance and have bad results.

I'm not sure this will help your decision but Castrol isn't a particularly good low-temp oil. For comparison:

code:

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Cold Cranking, cP Cold Pumping, cP

M1 15W50 5234@-4f 14050@-13f

M1 10W30 3848@-13f 10250@-22f

M1 0W40 4301@-31f 21700@-40f

GTX 10W30
GTX 5W30 pre>

---

In your situation, with 0*f as a low-end temperature, I'd feel better using M1 0W40 or 15W50 (or Delvac 1) year round. Sample at the first 3K to get a baseline and respond from there. You could probably run out to 5K or more, and you'd risk fewer side-effects from mixing oils.



David

 

[Dr. T]

I've always wondered the same thing. Seems like the thinner stuff (5-30 and 10-30) can't make the required HTHS of over 3.5? and so unless it's below 32F, Euro. manufacturers spec. out a 40 weight. I do find it weird that we're all concerned about winter performance when it only reached 0F in the colder regions of the N.A. where MOST of us live...and then we brag about a certain oil having a -50F pour point. A friend of mine said it was -4F in Munich last week!

However, what I have been able to deduce is that Euro. manuf. are (have been) more concerned with high temp. protection...hence, the 40 or 50 weight...and recognize that the split millisecond that a 5 weight "flows" better at 30F won't make a rats difference in wear compared to a 15 weight since the parts are already coated with oil to begin with.

Additionally, the oil spec'd needs to be able to last the 5 light interval on your dash (~7500 mi.). A 5-30 can't do this...I've tried. The only currently available BMW synthetic oil is the BMW 5-30 synthetic which is very good, but it too will begin to burn off after about 3-4k mi. and begin causing sludge only visible after tens of thousands of miles later. I've used it extensively in my `94 and stopped last year. Don't recommend it for your `91. Either the new engines are designed differently or Euro's are catching on....why make the car last beyond the warranty period. Come on guys...we have to sell new cars!

Your thinking re: winter use of 15-40 vs. 15-50 is not correct. Both oils are a 15 weight and will perform the same in the winter....with the exception of the synthetic performing better (more uniformity of the particles).

I'm currently using M-1 15-50 in my 1994 BMW...it's been down to -8F so far this year in Toronto. No problems thusfar.

As far as the new models...I have opened the oil cap on a 2002 325i and found it interesting that the area below the filler cap is black plastic masking any visibility of the engine. Furthermore, there was some comsumption on the brand new engine at ~9k km (6k mi)....with the computer saying there was another 4500km left on the oil. So I wouldn't be surprised if they didn't use the 5-30 in Germany on this car. In N.A., most of us feel a car engine needs a rebuild after ~150k mi...

Extrapolating to chevy's?? Hard to say. I've only owned a few cars my life...most have consumed 5-30's in varying degrees...in retrospect...I wonder why and why we see so much sludge...no wonder people are stuck on the 3k intervals. Interestingly enough, Ford says "use 5-20" in new Mustang, and then uses M-1 15-50 in the Cobra R.

 

[Pablo]

I am very biased, but Amsoil Series 2000 20W-50 is a pretty darn good oil in my Volvo turbo....I think it would be a great fit for a BMW.

 

[JBRIII]

I had a 85 BMW 318i. BMW at the time used Castrol 20W50. I wasn't used to that heavy of an oil at the time. It was extremely thick during winter use. Had to really let it warm up before it would go anywhere. They (the dealer)put it in year round. I think a synthetic would give much better flow rates, especially in the cold weather.

I'd just go with what the recommendations are and pick a good synthetic, like Mobil1.

John

 

[Ken2]

quote:

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Originally posted by Dr. T:
I've always wondered the same thing. Seems like the thinner stuff (5-30 and 10-30) can't make the required HTHS of over 3.5?
......

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Schaeffer #701 5W-30, #703 10W-30, and #705 20W-50 are all ACEA A3-02 and D-C 229.3. I'd like to know how they achieve the high HT/HS with 30 wt.


Ken

 

[G-MAN]

quote:

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Originally posted by Ken2:

quote:

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Originally posted by Dr. T:
I've always wondered the same thing. Seems like the thinner stuff (5-30 and 10-30) can't make the required HTHS of over 3.5?
......

---

Schaeffer #701 5W-30, #703 10W-30, and #705 20W-50 are all ACEA A3-02 and D-C 229.3. I'd like to know how they achieve the high HT/HS with 30 wt.

Ken

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Because they are on the upper end of the 30wt range. There are six oils that meet the MB 229.5 spec and all of them except Mobil 1 are 5w30, and these are all A3-02 oils.

 

[Patman]

Actually Schaeffer 10w30 is not at the upper end of the 30wt range, but at the lower end. In my last test, which was basically a virgin analysis since it only had 740 miles on it, the viscosity came out to 10.0 cst at 100c.

It's why i want to mix in 15w40 this summer, so I get the viscosity closer to 12 or 13cst, which I feel my almost 80,000 mile LT1 will like better.

 

[G-MAN]

quote:

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Originally posted by Patman:
Actually Schaeffer 10w30 is not at the upper end of the 30wt range, but at the lower end. In my last test, which was basically a virgin analysis since it only had 740 miles on it, the viscosity came out to 10.0 cst at 100c.

It's why i want to mix in 15w40 this summer, so I get the viscosity closer to 12 or 13cst, which I feel my almost 80,000 mile LT1 will like better.

---

Yeah, but if you look at Schaeffers tech sheet for the 7000 10w30, it lists the 100*C viscosity as 10.00-12.00. I laud Schaeffers for being forthcoming enough to show that viscosity for any given brand and grade of oil can vary. I would say, however, that it's only the batches that are close to 12.00 that can meet the A3 spec with a HT/HS of 3.5, and that the 10-12 range is probably a perfectly acceptable variance in the industry.

 

[mdv]

quote:

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Originally posted by JBRIII:
I had a 85 BMW 318i. BMW at the time used Castrol 20W50. I wasn't used to that heavy of an oil at the time. It was extremely thick during winter use. Had to really let it warm up before it would go anywhere. They (the dealer)put it in year round. I think a synthetic would give much better flow rates, especially in the cold weather.

I'd just go with what the recommendations are and pick a good synthetic, like Mobil1.

John

---

I currently use a synthetic 15W-40 in a 90 325i, and personally think it's a tad thick for cold weather use (single digits here) based on my oil pressure gauge. I'm not sure if it's going to be able to maintain a decent oil pressure at idle either in the summer. In that case, 20W-50 (synthetic) is going in for the summer, and the winter will be a 10W-40 synthetic.

 

[TooSlick]

JHM,

German manufacturers have traditionally recommended 15w-40/15w-50/20w-50 petroleum based oils for high temp service. This was typically done due to the very high, sustained oil temps you would see on the Autobahn. With petroleum oils, it was necessary to use heavy oils in order to maintain adequate oil pressure and prevent accelerated wear.

Current specs for all German manufacturers now typically recommend 0w-30/5w-30/0w-40/5w-40 synthetic lubes for all temps. Even Mercedes now recommends 0w-40 and 5w-40 grades for year round use and they tend to be VERY conservative about these things. Porsche actually came out with a separate oil viscosity/temp chart for synthetic lubes in the mid 1990's that allowed for the use of low viscosity oils, even in the 911 engines.

I've been running 0w-30/5w-30/10w-30 synlubes year round in Vw/Audi engines for 17 years with excellent results. For this particular BMW engine, I'd probably start out running Mobil 1, 10w-30 year round - supported by some oil analysis testing in the hotter months. If you run into oil consumption or wear related issues with the 10w-30, I'd simply use the Mobil 1, 15w-50 during the 3-4 hottest months of the year and use the lighter stuff the rest of the time. However, I'd be honestly surprised if you have any problem running the 10w-30 year round, since it works fine in these very high revving Japanese motors.

The 15w-50/20w-50 synthetics are normally only necessary in excessively worn engines that burn and/or leak a large amount of oil, or for competitive racing applications.

 

[Patman]

quote:

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Originally posted by G-Man II:

quote:

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Originally posted by Patman:
Actually Schaeffer 10w30 is not at the upper end of the 30wt range, but at the lower end. In my last test, which was basically a virgin analysis since it only had 740 miles on it, the viscosity came out to 10.0 cst at 100c.

It's why i want to mix in 15w40 this summer, so I get the viscosity closer to 12 or 13cst, which I feel my almost 80,000 mile LT1 will like better.

---

Yeah, but if you look at Schaeffers tech sheet for the 7000 10w30, it lists the 100*C viscosity as 10.00-12.00. I laud Schaeffers for being forthcoming enough to show that viscosity for any given brand and grade of oil can vary. I would say, however, that it's only the batches that are close to 12.00 that can meet the A3 spec with a HT/HS of 3.5, and that the 10-12 range is probably a perfectly acceptable variance in the industry.

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That varience kind of bothers me though. When selecting an oil, some people like myself want to know if they are getting a thin 30wt or a thick one. Varying from 10-12cst from batch to batch is kinda scary in a way, as one time you'll get a high 30 and the next time a low 30. So when you get the low 30 you might have more engine wear than when you have the high 30.

 

[G-MAN]

quote:

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Originally posted by Patman:
That varience kind of bothers me though. When selecting an oil, some people like myself want to know if they are getting a thin 30wt or a thick one. Varying from 10-12cst from batch to batch is kinda scary in a way, as one time you'll get a high 30 and the next time a low 30. So when you get the low 30 you might have more engine wear than when you have the high 30.

---

I honestly think that sort of variance is the norm. If you look at the spec sheets for virtually any oil you will find somewhere on it a disclaimer that will say something like "the physical characteristics listed are typical and may vary." I think many of the VOAs posted to this forum bear this out.

 

[Dr. T]

TooSlick, I don't completely agree with that statement. The first part was good...but then...

Not knowing how Audi/VW works, I ran BMW 5-30 fake synthetic for ~60k mi. after they switched from the 5-40 synthetic in my 1994 BMW for 2 yrs. with increased consumption up to where I began noticing visible sludge build up and decreased power...something was wrong. Running the same manuf./computer determined oil intervals of ~7500 mi. I needed to add about 1/2 qt. of the 5-40...the 5-30 went up to 1 and then 2 quarts...again I knew something was wrong. And yes it's ACEA A3 rated or whatever, but it was too thin. You want to know what the correct grade is? The lowest grade/thinnest oil possible without EVER consuming a drop. Why? Because you don't have and won't ever have engine wear.

As far as the new specs...told ya, coupled with the new oil and new oil technologies...they're learning from the U.S....interestingly enough...Castrol's selling the 10-60...wonder to whom? Not to Ford...

 

[FowVay]

For the 1991 318i there were two chassis. The earlier E-30 chassis recommended 10W-40 mineral oil. The later E-36 chassis with the newer M40 engine recommended 5W-40, 10W-40, or 15W-40.

Since you do numerous cold starts i'd choose the oil that flows the quickest. There are several 5W-40's on the market that would fit your application. Valvoline, Quaker State, Pennzoil, 76, Agip, and Shell all sell oils in North America that are recommended for your application. I'm certain that there are others but the list I've cited all meet the 'Long Life' requirement specified by BMW on their newer vehicles.

 

[sprintman]

All the major manufacturers syn's here are 5W40 only. Delvac 1 or Redline 5W40 is the go IMO. Patman I'd try either of these in your Gm engine?

 

[Patman]

quote:

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Originally posted by sprintman:
All the major manufacturers syn's here are 5W40 only. Delvac 1 or Redline 5W40 is the go IMO. Patman I'd try either of these in your Gm engine?

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Both of those oils are very expensive here though. Especially Redline, it's $17 to $20 a quart!

I'm going to try mixing Schaeffer oil to get the desired viscosity I want and see how that changes my wear numbers. My goal is to see single digit wear numbers on the 6k sample.