Manuf. calls for 5W30 vs 5W50 or 15W50

[chefwong]

If you want engine longevity, even though its not a BMW recommendation (but BMW doesn’t say its deleterious either), switch to a 5W-50 or 15W-50 synthetic engine oil as the higher viscosity (thickness) oil will keep the moving parts separated, albeit with the consumption of a smidgen more fuel.


Just curious to see what your take is on this statement. I believe the person that posted this was a a oil engineer. FWIW, I've used RL 5W30 and currently GC in my BMW X5 V8 engine. The crankcase hold a whopping 8.5 quarts. Am I better off running something thicker during the summer to keep wear at a minimal ?

 

[TC]

"Use a 50wt when the manual calls for a 30wt to keep the moving parts separated..."

I think it's safe to assume that not all engines are "50wt" engines when hot -- one size doesn't fit all. While addressing both CAFE standards and cold start needs, as well as how these influence recommended oil weights, Quaker State goes on to claim, "While one manufacturer's engine may require an SAE 10W-30, another manufacturer's engine may require an SAE 5W-20 viscosity grade. This is likely due to different tolerances within the engine or other engine design factors."
http://www.quakerstate.com/pages/carcare/whattoknow.asp

 

[sprintman]

You will get a squillion answers both thick or thin or med viscosity or whatever. An on-going debate that never ends.

 

[Jelly]

For street service, stick with BMW's viscosity recommendation.

Here's a good read: http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=1;t=000293;p=2#000064

 

[Doug Hillary]

Hi,
chefwong - I agree with Jelly. Of all the engine manufacturers, BMW should know best what works and what doesn't! They had enormous problems with their M3's at one stage and while this was due to manufacturing and quality control issues they did review their oil recommendations at that time. Some engine families went to Castrol R 10w-60 which is their (Castrol's) "over the counter" racing synthetic and an oil I am very familar with (since the 1970s)

They (BMW) work very closely with Castrol at F1 level and of course their factory fill is Castrol! I think Castrol have a permanent complement of Lubricant Engineers based at BMW's research centre in Germany.

As well, only oil on BMW's Approved list should be considered for use

When engines have such things as VANOS and double VANOS and VALVETRONIC engine management controls and etc. the choice of oil viscosity and construction becomes quite critical. Flow (cold and hot) becomes especially important and the oil's cooling abilities are critical too

My BMW Z3 2.8 has single VANOS and performs much better on a 5w-40 than it did on both 0w-40 and 10w-30 which are both recommended grades and on their Special Oils or Longlife Oils Lists. It mostly runs at an oil temperature of 100-105C even at an ambient of 42C

Regards
Doug
MY02 Subaru Outback 2.5 manual (Delvac 1)
MY98 BMW Z3 2.8 manual (Delvac 1)
MY89 Porsche 928 S4 Auto (Delvac 1)

 

[JHZR2]

the redline 5w-30 should give a larger film thickness than competitive 30 wt oils, probably more indicative of a 40wt oil. It is a fine choice IMO, so long asyou ensure that the engine isdriven at least 15 or 20 miles a few timesa week, as ester oils arent that friendly to water.

JMH

 

[ekpolk]

Did I miss something? Where did that statement come from?

I think Doug makes an excellent point. Many modern engines use oil for purposes beyond what you think of as basic oil functions. A critical example is the variable valve timing systems that are appearing on more and more engines every year. Many of these systems are hydraulically actuated and use motor oil as their hyd fluid. Toyota's VVT-i is a classic example. The disc affairs fitted to the end of the VVT-i cam shaft have a dual chamber system in which oil is pumped into one side or the other depending upon how/when the ECU wants the valves to operate. I would assume, safely I think, that both the ECU and the "physical" part of the hyd system are calibrated to run of oil of (or at least near) the specified viscosity. And I shudder to think what happens if one of these engines gets neglected and sludge and varnish get into the VVT hydraulics.

 

[Dr. T]

Doug, the problem is that in N.A., BMW uses a 5-30 that has proven that it cannot do a 10k interval without incurring engine problems by 100k. I have these engine issues in my BMW by using this regimen.

Then you have the BS scare tactics of those on these boards that subscribe to the "you may not have a 50 weight engine". Guys, there is no such a thing. You can use any weight of oil in any engine created by man depending on the outside ambient air temperature conditions as the ONLY variable consideration!

Lastly, I dont' know about you guys, but mori's 122k Audi engine pics using 5-50 every 10k tells it all without saying a word. Try that with a 5-20 and tell us that your UOA's look great.

 

[cousincletus]

I agree w/Dr.T. I have seen many engines go for well over 200K on 15W-40 truck oil. Both Ford and GM recommended 5W-30 for those years.

 

[Jelly]

quote:

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Originally posted by cousincletus:
I have seen many engines go for well over 200K on 15W-40 truck oil. Both Ford and GM recommended 5W-30 for those years.

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You're starting to sound like me...

 

[1 FMF]

quote:

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Originally posted by chefwong:
FWIW, I've used RL 5W30 and currently GC in my BMW X5 V8 engine. The crankcase hold a whopping 8.5 quarts. Am I better off running something thicker during the summer to keep wear at a minimal ?

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I've run pennzoil 5w-30 and supertech full-syn 10w-30 in my '02 last summer. I have an oil temp gauge, and saw 220-270F oil temps when outside temp was 75+. I did a run with havoline 10w-40 and noticed that oil, with same outside temperatures generally, would run as low as 195F on the highway. That never happened with the 30 wt oils. I have a UOA posted of a havoline 10w-40 in the uoa section. I run 6 qts oil, and outside temperature plays a big factor on oil temperature. If you have a larger capacity crankcase and oil pan, I would expect the oil to run cooler, but a 40 oil may help more especially in summer weather. FYI- in < 40F weather my oil temp now running castrol 0w-30 after a 15 mile highway drive to work will hit 190 F if I'm lucky, so from that observation a 10w-40 oil any time other than hot summer for me is not worth it.


My knowledge is limited on bearing design and variation amongst engines. Regardless, I thought all bearings have a certain "clearance" range and no bearing is any different from another, except for overall size? So engines call for anything between 5w-20 to 10w-60 aren't running any vastly different bearing clearance. Such is the case of the Dodge Hemi V-8 when it came out a few years back, initally called for 5w-30. Then Dodge jumped on the 5w-20 bandwagon and that same motor, without any design changes to my knowledge, then ran 5w-20. It was either 2002 or 2003 to the following model year. I don't think anyone will argue that the push behind 5w-20 oil is mostly for fuel economy and not engine longevity. As for running higher viscosity oil, I fail to see how a 50wt oil at 25 cSt at 100C operating temperature is going to be bad for a bearing where an engine calling for 5w-20 oil when the 5w-20 oil will be 50 cSt and higher at temperatures of 40C/104F and lower. So what if you're car never warmed up fully and always ran 160F and lower oil temps?
It's all about efficiency. Lower viscosity = less friction, not wear and longevity.

 

[ekpolk]

quote:

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Originally posted by Dr. T:
[QB{snip}
Then you have the BS scare tactics of those on these boards that subscribe to the "you may not have a 50 weight engine". Guys, there is no such a thing. You can use any weight of oil in any engine created by man depending on the outside ambient air temperature conditions as the ONLY variable consideration!

Lastly, I dont' know about you guys, but mori's 122k Audi engine pics using 5-50 every 10k tells it all without saying a word. Try that with a 5-20 and tell us that your UOA's look great. [/QB]

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Doc, don't these two statements contradict one another? The first one looks like you're saying any oil will work (dependent on air temp), then the next statement suggests that lightweight oils don't work.

Additionally, isn't the internal temp of the engine more important to the oil and its operating vis than outside air? An engine that's running within the parameters of its cooling system does not care that the outside air temp is. Or am I missing your point?

 

[1 FMF]

quote:

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Originally posted by ekpolk:
isn't the internal temp of the engine more important to the oil and its operating vis than outside air? An engine that's running within the parameters of its cooling system does not care that the outside air temp is.

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More important or more significant, yes. But outside air temperature plays a very big part also and you must account for it. As to how much significance depends on the car, engine type and material, cooling system design, capacity, etc.
My post above illustrates this, on an '02 Camaro. 14 qt cooling system, no room for radiator and air flows from underneath car into radiator as opposed to through front grill. I think the car exceeds the cooling system limits in 90F + temperatures when in stop and go traffic. Little air flow causes coolant temps to run 220-240F easily and it can get that high very quickly from the normal operating temp of 190-200F, causing the electric fans to kick on. This won't happen in winter time, or takes a much longer time to happen in consistent stop & go driving under 30 mph. As a result, oil temps easily run 220+ in the summer, depending on driving conditions, versus hitting 210F max wintertime. This is with a 190F thermostat. Due to the much colder air temp in wintertime, coolant temps are more likely to stay down around 190-200F all the time, as well as keeping oil in the pan and block cooler. It's an all aluminum motor by the way. In summer, the hotter air is less able to keep the coolant at 200F or help cool the block at all, and the result is much higher oil temperatures. For the 30-50 degree F temperature swing I've noticed since having an oil temp gauge, nothing has changed other than the outside air temperature with the exception of oil changes.

 

[Dr. T]

The clarification is:

Lightweight oils (eg. 5-20) work fine....as long as you don't use them at hot temps. eg. over 10C. So the statment was referring to using them exclusively year-round in all climates...eg. summer at 35C.

Re: internal vs. external temps....the external temp. is what is felt when the engine is first started ie. if it is -25C outside and the car was sitting all night outside, then the engine and and it's oil will be at -25C. Therefore you need at least a 10W.

In the summer, the cooling system (assuming it's working properly) will keep things at bay. However, when the car is shut down....internal temps will skyrocket because oil circulation is ceased....for eg. the very reason it's good practise to continue running a turbo engine for a couple minutes before shutting it down. IMO, this is when most of the varnish/sludging/coking etc. occurs...so the oil better be able to take the heat.

 

[nel]

What's interesting to me is that BMW has changed its recommendations quite a bit over the years. This may be a function of the improvements in oil, or the need to improve the fuel economy of its fleet, or both. Nonetheless:

my '95 525iT: 20W50 dino
my wife's '97 328i: 10W40 dino
current BMW's: 5W30 Group III, 10W60 for M3's

As far as I know, the metallurgies and clearances have not changed in the BMW inline-sixes.

I've been running 15W40 on the station wagon with good results, and have a blend of that with 5W30 right now (UOA in June). What do you want to see next? 0W30? 5W50? I'm willing to experiment...although, I think in my mild California climate that any differences in wear would not be statistically significant.

 

[Dr. T]

Yeah, that's BMW N.A.. In Europe, they use 0/5-40. Most of it is due to synthetic use. There is an underlying thought that with synth's you don't need to go with the gusto viscosities of old. While agreeing with doing away with 20-50, I don't completely agree with 30 weights doing 10k OCI's.

Secondly, there is an increased turnover of vehicle design and sales. Leasing is king. Even the Germans have figured it out. Make things disposable..and sell, sell, sell....especially in N.A.. So with that in mind, just dumb down the viscosity and use one for all...hence, the 5-30...until there's problems:

One, M engines spinning bearings. Solution: use what they use in the fatherland: 10-60.

Two, valvetrain issues on 10k 5-30 OCI's. Solution: Use what they use in the fatherland: 0-40 (as per a BMW TSB (service bulletin)). Why not use the 0-40 from the start? Fuel econonmy? Maybe. Sales? Now you're talking.

 

[AEHaas]

I have used Mobil One 0W-20 for several years now in southerly Sarasota Florida, all year. My operating oil temperatures and pressures have remained essentially the same at all times. There has been no penalty in my oil analysis.

aehaas

 

[Dr. T]

5-20 for several years? In what engine? How many miles? What is your oil change interval?

My guess is...

You haven't used it for 10 years. It's not a high hp/low displacement OHC high-temp. high-revving European engine. You don't have 400+ miles on the car. And you don't change your oil at 10k+ OCI's...

 

[2KBMW]

Chefwong. I'm with Dr.T. I use Castrol
Syntec 5w40. Same synthetic oil and specs
as Europe's Castrol Softec TXT synthetic.

 

[Patman]

quote:

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Originally posted by Dr. T:
5-20 for several years? In what engine? How many miles? What is your oil change interval?

My guess is...

You haven't used it for 10 years. It's not a high hp/low displacement OHC high-temp. high-revving European engine. You don't have 400+ miles on the car. And you don't change your oil at 10k+ OCI's...

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aehaas drives a Ferrari actually (a fairly new one too)