Anybody Use Straight WT Oil - Page 2 - PeachParts Mercedes-Benz Forum

mannys9130 · #16 02-25-2016, 12:40 AM

The fact doesn't change that higher pressure leads to lower flow. A relief valve opening doesn't increase flow to the bearings.

Like I said, no authority to speak.

leathermang · #17 02-25-2016, 01:00 AM

Quote:

Originally Posted by mannys9130

The fact doesn't change that higher pressure leads to lower flow. A relief valve opening doesn't increase flow to the bearings. .....

1. Higher pressure leads to more flow if the friction remains the same.. so that is a crazy statement.

2. You were saying that if the oil were too thick it could harm the bearings.. but the relief valve protects them from that...

babymog · #18 02-25-2016, 08:49 AM

If single-viscosity oils became obsolete decades ago, then so did multi-viscosity dino oil. OTOH, the cars being discussed here are also obsolete, ... 30+ years?

Group IV synthetics have been available for 40years, and have in my experience shown less suspended wear particles in oil analysis (= less wear) even in extended change intervals (have been doing oil analysis since long before it was a fad), typically have better additive packages, return better fuel mileage, are better at reducing sludge, are in many ways better.

Dino multi-viscosity oils are blended oils, a thin oil with an additive package to keep it from thinning as much as the basestock when warmed, to give it a multi-viscosity rating (a single viscosity oil is the standard, if it thins less as it warms than old-school non-blended oil then it earns a higher 2nd number ex: 10W-30 is basically an SAE-10 oil when cold, and an SAE-30 oil when warm).

One major problem with this formulation is that the viscosity modifiers typically don't shear well, and your 10W-30 on a flat-tappet engine will shear (protect) more like an SAE-10 than an SAE-30, which is why many industrial engines require single-viscosity oils. They are BETTER in some conditions and if you were to drive your Mercedes diesel gently until up to normal operating temperature, and drive lots of extended miles, you'll be fine and your engine will likely be happier without a multi-viscosity dino oil. There is also the viable argument above about mid-life and older engines having higher than original clearances and different oil needs than new.

There are many reasons that multi-viscosity dino oils are obsolete, and will void warranties in several higher-performance and tighter tolerance engines, and IMO anyone who will tell you that one oil is obsolete and the one they use is not, ... well we're all taller on the internet aren't we? Personally, and from my experience / research, I will never NEVER put a multi-viscosity dino oil in a car that I care about. Sure the company car gets whatever the dealer puts in it, but it goes 100k and gets turned in, no reason to sweat it.

Remember also that the oil type in your manual is the minimum requirement, and that it was the best all-around oil recommendation for the time. In newer cars there are very thin oils specified, this helps viscous drag and pumping losses and improves fuel mileage and emissions, ... and the engines are designed to survive with this thinner oil.

There's a lot of good information on this site, the bobistheoilguy link has some good information also, not complete nor completely objective IMO, but a good primer, just don't think that one internet site or one reference is considered solid research (our Chemical Scientists will quickly point out the flaws in that one!).

I feel that running a good Group IV synthetic for an oil change is a good idea to see if your lifters like it. Possibly not, but it will dissolve some of the sludge clogging oil passages and hanging around the pan. Which is not always a good thing FYI, it will also dissolve the sludge around seals that slows the leaks, and most older engines will leak more with syn oil than with dino oil.

mannys9130 · #19 02-25-2016, 09:23 PM

We drive these cars in the modern world today and use products of today to maintain them. To argue that the car is obsolete therefore obsolete products are fit for use is definitely silly. If that's the case, we shouldn't use HPR diesel, covert loop glow plugs to pencil, use AGM batteries, use new formulations of detailing products, use new tires tread technology, or any other advancement made since the cars were designed.

I don't see how you could drive these older diesel "gently" while warming up. They make peak power at a fairly high rpm, and since they don't make a lot of power in the first place driving safely requires all of that power be demanded. If you were to try to drive your cold 240D onto the road and drive it under 2000rpm until it warmed up, you'd probably be run off the road. Therefore, using a multigrade oil that is thinner when cold, you can attain higher RPM without reaching the point where the oil pump can't provide additional flow and protection of the bearings.

The difference between a 0w-40 oil and a 15w-40 oil is not noticeable at operating temperature. To say that the use of thinner oils is due entirely to drag-decreasing reasons or because the engines were designed to survive on them isn't the whole story. The 0w will flow much faster and present much less resistance to flow when it's cold. The 15w will be very thick and it will refuse to flow enough volume to protect the bearings much sooner than the 0w oil will. That cause metal to metal contact. That is damage. As long as there is oil flow enough to maintain a clearance between surfaces, hardly any wear occurs at all. At operating temp, and when the oil is able to flow when running cold hardly any wear occurs. At cold starts when the oil has drained down and the pump must pick it up and build pressure, and when the engine is revved high when cold are the two scenarios when engines experience the vast majority of the wear they will ever see. If you reduce the time that the engine runs dry at cold start and increase the rpm to which the engine can spin without the oil pump reaching its maximum displacement, you will greatly extend engine life. This is where multigrade oils shine, and straight grade oils fail miserably.

When engines age and wear, the clearances grow and people have a tendency to pour in thicker oil. What that does is actually make the problem MUCH worse. The thicker oil causes more oil starvation when cold, and causes wear to occur faster than it was before. This becomes exponential. Soon you'll find yourself wanting to pour in ridiculous grades of oil because the engine has worn so much from starvation that it isn't serviceable anymore. Staying with the recommended grade is what should be done, and any leaks should be fixed with new gaskets instead of a viscosity change. If an engine can't develop sufficient oil pressure with the OE oil grade, something is very wrong and a viscosity change won't fix it.

If an engine is always at operating temp and doing work (like a semi truck) then a straight grade oil is ok. Passenger cars aren't usually covering the distances semi trucks do without being shut down. The semi trucks spend very little time with their oil being too thick. Passenger cars spend a lot of time running with oil that's too thick, and they experience frequent cold starts (like every single morning...) that damage them every time.

I suggested 5w-40 synthetic oil in post #5. If you take my advice, you don't need to worry about any of the VI shearing you talk about. Viscosity is obtained differently between conventional and synthetics. Synthetic is vastly superior.

The choice is straight forward. A straight grade is WAYYY too thick when cold but the correct viscosity when hot. A multigrade is way too thick when cold but it is much MUCH closer to the desired hot viscosity and has less thinning to do before it's correct. If your engine is running for hours and hours on end and you spend all day driving, perhaps a straight grade wouldn't be horrible. If you drive your car like most people do, a multigrade is a must for minimizing engine wear.

babymog · #20 02-26-2016, 10:36 AM

Did you ask the OP how (s)he drives the car when "cold"? Did you consult an Engineer in the design of his engine on why the oil specified was specified (including the SAE30 and SAE40)? Do you know that these recommendations (apparently in the manual, and blessed by the original Engineering team) are contrary to the needs of the engine? Are you an Engineer?

I am an Engineer (retired), former member SAE, have spent most of my career in the Automotive industry, Mercedes-Benz and Daimler have been my customers for many years. I do not believe that they would recommend SAE30 and SAE40 oil in their manual unless it was determined to be a proper lubricant/coolant for the engines.

I also am able to drive my cars several miles before meeting any significant traffic, or "merging on the freeway", and have never had an issue with needing to rev an engine on cold oil. One of my cars specified a lower max. RPM until the oil temperature reaches 60C., which I adhered to for the 200k miles I owned that car, it's not that difficult.

I don't know if you're just trolling, or if you actually believe your own posts, I guess your next post will tell.

OM617YOTA · #21 02-26-2016, 11:09 AM

Using factory recommended oils and OCI, engines tend to wear out the cylinders before the bearings. Low compression or unacceptable blowby occur before bearing issues. Lawnmower or sports car, this has been my experience.

Interesting discussion, but probably a moot point.

vstech · #22 02-26-2016, 11:21 AM

Quote:

Originally Posted by leathermang

Ever looked at a blowup ( no pun intended ) of the 617 lubrication system ?
It is called a relief valve and it is before any bearings....
On page 18.8-005/1 f2 the numbers on the line drawing describe (1) as '' Oil pump with integrated pressure relief valve ''

However , IF you want the FSM to say what I have said.... then look carefully on 01.8-030/1 f2 in the 617.95 FSM
or 00.4-110/1 in the 615,616, 617 na FSM

It shows for constant ambient temperatures over 32 degrees F that three oil viscosity ratings are listed.... up to 86 degrees F.
those are ****Straight 30 wt ***, 20w-50 , 20w- 40
Note (1) states that at over 86 degrees F that *** straight 40 wt *** may be used. The stars were added by me in case your bias might cause you to misread the list.
So above 32 degrees F straight 30 wt and straight 40 wt are listed as acceptable oils for our engines.

I go heavier once an engine becomes ' high mileage ' , which I define as 100k miles and above, because as engines wear the clearance in the bearings becomes more and the thicker oil protects against metal to metal conditions better than thinner oils.

both of your points are correct. straight weight oil IS thicker than multigrade oils when cold... and the HOTTEST it gets in death valley CA is still cold to motor oil.

yes, the MB has provisions to prevent blowouts of oil passages and pumps/filters, but you gotta agree, the straight weight oils are not as good as multigrades in a lot of areas, and cold straight weight oil does strain the oil pump, and the bearings would momentarily starve of oil at startup with it.

will straight weight oil work in our cars? sure. is it better? it's debatable (obviously) but the whole point of using thicker straight weight oil for more worn engines seems silly... multigrade oil is not thinner than straight weight oil... it's exactly the same... at operating temp... it's got a better flow characteristic when below operating temp, and due to that I think bearing flow is improved sooner...

now, it's also possible that straight weight oil may stick to the passages better when the motor is shut down, giving better protection at startup... I don't know. I doubt it, but I don't know. I do know that thick oil is more difficult to suck into the oil pump, and more difficult to pump through the oil pump, and the oil passages, so, it's conceivable to me that at startup, the motor spins, and oil pressure would build up with straight weight oil, pop the relief valves, preventing oil from reaching the upper passages until the oil thinned enough to get pressure and flow to them...

does that make sense?

I can see where straight weight oil would be better at protecting a fully up to temp motor that has high clearances on the bearing surfaces... but I can see the multigrade oil keeping the clearances tight with better oil flow for more miles...

keep in mind this...

the Mercedes diesel has MASSIVE bearings... so even on an extremely high mileage motor... the clearances have not changed much unless it was run low on oil, or used in extreme cold climates that starved them of oil flow at startup...

I've always been taught starting a motor is a terrible thing to do to it... 99% of the wear a motor gets is from startup... so my thinking is... protect the motor at startup, and let it loaf during it's drive with fine oil.

babymog · #23 02-26-2016, 11:30 AM

John

I believe that the 61x series of engines have a backflow valve to prevent oil regression when shut down, which would mean that there is already oil from the pan, through the pickup, in the pump, in the filter and into the primary oil journals to the main bearings. When you start to crank the engine, the oil begins immediately filling the main bearings, into the crank and rod bearings, up into the cam oilers, etc. Besides that, have you ever pulled the bearings from an engine that hasn't run in a year? The bearings have oil on them, they are not dry. The oil pump is a positive-displacement gear pump, it will pump substantially the same amount of oil per revolution regardless of viscosity within reason, although it will consume more energy to do so with thicker oil. Pressure is limited downstream, which will create a correlation between flow and viscosity, as will bearing and piston clearance which changes more slowly with engine temperatures.

I agree that a multi-viscosity oil is more likely to protect an engine at higher RPM when cold, especially if the operator likes to start an engine with the pedal firewalled. Newer oils are better than older oils (in most cases, I'm sure there's a "lowest bidder" out there somewhere making inferior oils) and even the same viscosity oil that was made in the '80s is likely better now (although the elimination of TE Lead as a lubricant does move it backward somewhat, but many have replaced with MoS2).

The OP seems satisfied that for his uses the multi-viscosity is his better solution. For that purpose this thread is dead. As far as sweeping statements of straight SAE-30 or SAE-40 not being suitable for the engine though, my opinion is that nobody on this thread has shown that they can state as fact whether or not this is true, and stating it as fact is IMO a disservice to those reading this thread for information.

Further, it is my opinion that based on the fragility of the long-chain polymers commonly used as viscosity-modifiers in multi-viscosity dino oil, I do not feel that this is a good solution to protect an engine. This is why some prefer straight-viscosity oil over multi-viscosity oil in the right application (or better still IMO, a good synthetic).

If your concern is truly with cold-starts, be sure your glowplugs and timing are correct so that you can start at idle instead of needing to rev the engine. Install a pre-oiler to inject oil flow before you crank, and go over to mrmoly.com and order a couple of cans of their engine-aid .5micron MoS2 additive.

86-300sdl · #24 02-26-2016, 11:39 AM

Not only because of FSM approvals, my 45 years of wrenching observations including a few older vehicle motor rebuilds & a myriad of oil generations, the knowledge of a few here with similar or greater experience, 40 wt being thinner than warmed up recommended 20w-50 (drivers manual), and "warm weather conditions"....

I poured in the CJ-4 40wt.

Tied the stop lever back and turned the motor over a few revolutions 'cause some members scared me into thinking the straight wt. oil may not circulate to & through the top end. Started the motor and instantly the worn lifters that are in need of replacement (425k miles) were quite, telling me the oil is making its way to where it should be. Mind you that with fresh multi-grade (syn or dino), there has over the last ten years / 250,000 miles been some lifter noise at start up and not dissipating until she's been on the freeway a few miles.

Road Test: Yesterday I ran up to Los Angeles and back (150 miles) for work. 85 to 90* F outside. 75mph for 3/4 of the way, 10 mph traffic the rest. Motor is purring. Oil pressure at idle notched up from just under 2 bar to about 2.2 bar. 3 bar at 1000 rpm.

I repeat...no lifter noise at start up or afterward. I haven't experienced that in 250,000 miles lol....and the motor ran nice and cool.

I'll be running out to Phoenix for work next week. 5.5 hrs of 70 - 80 mph non stop each way . So I'll see....but I think it'll be just the same healthy 603 purr.

I'll probably renew the lifters before next winter, & when completed prolly go back to syn multi-weight because of cooler ambient temps. But for now I feel I'm getting better lubrication.

I'd like to thank y'all for your opinions / advice, especially Mr. "babbymoog" & Mr. "leathermang". You too "manny..."

P.S.
- I'm not worried about damaging bearings in that big ass diesel bottom end designed to handle a ton of load.
- Re warm up....I've always let any motor warm some (even our brand new Honda CRV - 10-20w oil) before putting a load on it. No different here.
- No reduction in idle oil pressure after 75 miles at 3,000 rpm were as with multi-weight it always dropped a bit after the motor warmed up and an hour or so of freeway miles.
* My leather seats even stopped squeaking. But that could just be the warmer weather. Anyone use multi-grade leather conditioner?

thatguy · #25 02-26-2016, 12:52 PM

Interesting results, glad it's working out for you. For a "non-commercial" application, yours sounds about as well-suited for straight grade oil as possible in a passenger car; hot temps, long open highway runs at operating temp, etc.

It'll be interesting to see how it holds up over the course of an oil change interval, see if fuel economy changes or lifter noise returns, or anything else out of the ordinary.

On a side note, I love the drive from So Cal to Phoenix on a hot day, the scenery changes are really cool and I love that stretch of I-10 that runs through Palm Springs, if you go that route. I always make good time after passing the hill near Joshua Tree, get good mileage out there on the open road as well. Probably the last place in Southern California where you actually have open highway.

86-300sdl · #26 02-26-2016, 02:36 PM

Quote:

Originally Posted by thatguy

Interesting results, glad it's working out for you. For a "non-commercial" application, yours sounds about as well-suited for straight grade oil as possible in a passenger car; hot temps, long open highway runs at operating temp, etc.

It'll be interesting to see how it holds up over the course of an oil change interval, see if fuel economy changes or lifter noise returns, or anything else out of the ordinary.

On a side note, I love the drive from So Cal to Phoenix on a hot day, the scenery changes are really cool and I love that stretch of I-10 that runs through Palm Springs, if you go that route. I always make good time after passing the hill near Joshua Tree, get good mileage out there on the open road as well. Probably the last place in Southern California where you actually have open highway.

I'll report in re oil holding up. Should only be 5 weeks till next change.

SoCal to Phx Hwy 8 route is longer by 40 miles or so but so much better road condition and better auto traffic wise. Also about 1/20th the truck traffic. Both take about the same travel time. I generally travel around 4:00am in the summer to dodge the heat...Nice at sunrise for sure.

mannys9130 · #27 02-26-2016, 02:41 PM

The reason why your lifters are quiet at cold idle is because the straight 40 is so thick it creates very high oil pressure and is so thick it doesn't bleed out of the worn lifter barrel. It sounds good, but that same effect is causing starvation of other components. I'd much rather replace the old lifters and use an oil that lubricates the entire engine better, than use a very thick oil and compromise everything.

When you take a garden hose and turn it on, it flows with VERY slight pressure inside the hose as long as the end is open. Put your finger over the end and close off the tip. The flow goes down, and you can feel the hose swell with pressure. Pressure is resistance to flow. If you put a relief valve on the side of the hose that opens at a certain pressure and you cover the end of the hose to reach that pressure, water will flow out the relief valve to increase fkow and decrease pressure but flow out the end of the hose won't change. This is why oil starvation occurs with very thick cold oil.

You'll find that in auto tech, band aid solutions can sometimes cause other problems to occur in addition to the one you're trying to remedy. Fixing the root cause is the best course of action if you want a proper repair.

leathermang · #28 02-26-2016, 02:57 PM

Quote:

Originally Posted by babymog

......If your concern is truly with cold-starts, .... Install a pre-oiler to inject oil flow before you crank,......

Now you are talking... there are threads in the archives about this....all the big expensive commercial diesel engines have these.... aircraft engines also....

86-300sdl · #29 02-26-2016, 10:28 PM

Manny

You are making a mountain out of a mole hill. Just saying

First of all I've acknowledged that the lifters are to be replaced in the fall. You already knew that...I asked you about lifter brands, and job difficulty. So you can drop the derogatory "band aid" comments.

Re: "So thick" ..."starving components", remember 40 wt is ultimately less viscosity than or equal to the 20-50wt & or 40wt that are recommended for a 603 in my climate by MB in both the drivers manual and FSM.

So we ain't starving nothing here. Rather simply improving the hydraulics of a 425,000 mile motor.

And of course the higher viscosity is slowing the lifter bleed. That is the whole logic point.

Thanks again for your thoughts

Quote:

Originally Posted by mannys9130

The reason why your lifters are quiet at cold idle is because the straight 40 is so thick it creates very high oil pressure and is so thick it doesn't bleed out of the worn lifter barrel. It sounds good, but that same effect is causing starvation of other components. I'd much rather replace the old lifters and use an oil that lubricates the entire engine better, than use a very thick oil and compromise everything.

When you take a garden hose and turn it on, it flows with VERY slight pressure inside the hose as long as the end is open. Put your finger over the end and close off the tip. The flow goes down, and you can feel the hose swell with pressure. Pressure is resistance to flow. If you put a relief valve on the side of the hose that opens at a certain pressure and you cover the end of the hose to reach that pressure, water will flow out the relief valve to increase fkow and decrease pressure but flow out the end of the hose won't change. This is why oil starvation occurs with very thick cold oil.

You'll find that in auto tech, band aid solutions can sometimes cause other problems to occur in addition to the one you're trying to remedy. Fixing the root cause is the best course of action if you want a proper repair.

cornemuse · #30 02-27-2016, 10:46 AM

I have only ever used straight 30w (pennzoil) (since about 1964). Where I live it has not been below the mid 40's in many years. Havent seen frost at home in several years, (frost at work, tho) Just does not get cold enough here for me. (last new car for me was '79 Rabbit diesel, 30w, natch')

-c-