My new theory on engine tolerance design and oil specs

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JHZR2

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Hi, Today I was thinking about it a bit, and I kind of came up with a new idea... Oil analysis isnt new, nor are rheological measurements. Therefore, it must have been a well known fact for some time that oils will often shear down to lower viscosities when the get ~3000 miles on them, sometimes before. 5w-30 oils havebeen used for a while (Im using them as an example because it seems that they especially like to shear down to 20 oils). I believe that manufacturers know full well that oils will shear down, and therefore design the tolerances of engines to be able to be optimally lubricated with an oil of ~5w-20. I base this on a number fo facts: -Tolerances in engines have not changed in many years -Ford went from reccomending 5w-30 to 5w-20 without changing engine design, BUT made a new specification with extended tests to make sure the thinner oil could stand up and protect over longer times (a 20wt will work, buta 10wt is too thin, so it must stay in 20 grade for longer times, whereas a 30 grade can thin out and be OK) -My BMW reccomends 40 & 50 wt oils in the summer and most of the time, and 30 wt oils when below 40F. At operating temp, all these oils should be the same temperature inside the engine, and so it is logical to say that since they 'ok' a 30 wt oil, it will do just as good of a job protecting as a 50 wt oil at full temp. So the tolerances arent designed for a 40 or 50 wt oil, but really for a 30. -It seems from UOAs that a lot of oils that have thinned down to ~20, or oils that almost start that way (like M1), still often produce excellent wear numbers, even though they are a lot thinner than the manual suggests) From these ideas, I would say that my chevy truck (s10 ZR2), which more or less should only use 5w-30, is probably designed for optimal lubrication of an oil that is '20'->~'25' at operating temperature knowing full well that the oil in there will shear down to this viscosity. This would also explain why engines can go hundreds of thousands of miles when oil is changed every 3k, because the viscosity is always just slightly higher than the optimal point. Also, it would explain why it feels to me that vehicles often feel bogged down when using '40' oil compared to a '30', when designed for '30' oil when fully hot... Because it would run best on an oil that is 20ish, and to be up at 40 is too high of a spread, so viscous friction becomes a real issue, posing troubles... To have new oil that is 30 isnt too far away, 40 is just too thick. OK, so this is real long, I apologize for the length of the post, but this is my idea, and I wanted to get it out so anyone could comment on the potential validity of the idea [Smile] [Dummy!] [I dont know] [Duh!] [Bang Head] [Thumbs Down!] Thanks JMH [ March 16, 2003, 10:51 PM: Message edited by: JHZR2 ]
 
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quote:
It seems from UOAs that a lot of oils that have thinned down to ~20, or oils that almost start that way (like M1), still often produce excellent wear numbers, even though they are a lot thinner than the manual suggests)
I think you make alot of good points and I agree with them. I know that when I ran S2000 in my car and it thickend up to a 40wt, my car seemed a bit sluggish. I'm now running M1 and it feels a little quicker. I don't think though that a 40wt oil is too thick for certain engines. You might loose performace, but you gain protection in ht/hs. I also think certain engines do have better tolerances then others, mainly Japanese engines. I definitely think auto manufacturers realize this too and that there havn't been any real issues with wear in terms of the oil thinning to a 20wt. from a 30wt. Consumption is another issue and this is where I have a problem with M1. It's NOAK numbers are good, (not as good as Amsoil's) but there light 30wt. causes problems in high mileage engines. Amsoil told me that Oil Analyzers said a grade up or down is allowable. [ March 16, 2003, 11:20 PM: Message edited by: buster ]
 
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bering clearance is the space between the crankshaft journal and the bering ,the tolerance is the difference between the all of the crankshaft journals or the limits of machinework error . For example the main bering clearance may be .0015 to.0025,so anywhere between these is o,k. The best would be the same measurement on all the journals measuring exactly .0015, smaller giving the longest life of the components less slop =less wear I learned this in a helicopter repair class lots of spinning parts in helicopters. small clearances and quality control equals high tolerance and potential long engine life that receipe works for the Japanese motors
 
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JHZR2 I agree. I tried to capture some of this idea in the post below. The key point is that most users have been using 20W oils without knowing it due to shear loss.
quote:
posted March 04, 2003 02:09 AM -------------------------------------------------------------------------------- So my guess is that the oils of today depend more on modern boundary protection instead of HTHS to get the acceptable wear. In the past, this might not have been an option- don't know for sure. The trade-offs today might be perfectly acceptable especially if boundary conditions are no worst than a higher HTHS oil. The UOA reports seems to bear this out with some of the lighter oils. When you add in the factor of better VII that do not thin, then this all makes even more sense. Since most oils dropped a grade anyway in the past. We have been testing 20W oils for years, I fear.
 
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JHZR2, this is what I've been saying all along. There are no engine 'design' differences and any oil including salad oil will lubricate an engine. But, this isn't the point... This is why `90's BMW's "list" the 5-30 as an acceptable oil at temps up to -5C because these oils exist and work...but, only up to this temp.. What does this mean? At temps. above this, it is too hot (especially when engine is shut off +/- the a/c working at higher temps.) you need an oil with more cohones. The reason why your cars 'feel' sluggish with 40 or 50 weights is because years of 30 weight use has caused build-up that is now acting as an interference with the thicker lube. How do I know? I used to use BMW's 5-30 year 'round for the past 2 years...when I noticed increased sludge buildup, I switched to M-1 15-50 and woah..the car ran like garbage. I thought: "this can't be right?". But, with judicious use of Delvac 1 and a couple of short cycle oil changes, the car ran better with each mile. Probably the best solution is to use auto-rx before trying these oils. Nobody mentions this, but I've found you cannot simply use thicker oils if your car has been on a steady diet of 20 or 30 weights. You need to remove the crap so that these oils can now (as they should have in the first place) replace the crap that built up and lubricate properly/effeciently. This is why auto-rx is so popular here...and would work the best if used first.
 

Patman

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quote:
Originally posted by Dr. T: The reason why your cars 'feel' sluggish with 40 or 50 weights is because years of 30 weight use has caused build-up that is now acting as an interference with the thicker lube. How do I know? I used to use BMW's 5-30 year 'round for the past 2 years...when I noticed increased sludge buildup, I switched to M-1 15-50 and woah..the car ran like garbage.
But it's not the viscosity (5w30) which caused the sludge buildup, it's the choice of oil. If you ran 5w30 Redline, Schaeffer, Amsoil, Royal Purple or Mobil 1, I could virtually guarantee you wouldn't see a sludge buildup at all. If BMW's 5w30 caused the sludge buildup, it wasn't due to the viscosity, it was due to the poor quality of the oil. A well built 5w30 will not cause sludge buildup. [ March 17, 2003, 10:51 AM: Message edited by: Patman ]
 

JHZR2

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My truck has relatively low miles, ~34k, and has only had a diet of pennzoil, GTX or M1... And it was always changed at 3000 miles. I can't imagine slugdge is that big of a deal in my engine... At the same time, what you say makes a lot of sense... JMH
 
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Sorry, but I gotta disagree on this one. I think most of the manufacturers' oil recommendations are based on marketing first, protection second, & mechanical interface third. Now, this doesn't mean they don't care as much about engine protection & performance, only that it's not where the recommendations come from. Example 1: It's been discussed here before how the same vehicle/engine sold in one part of the world is given a different oil spec than in another part of the world. If the climate is similar in two regions of the world, why spec different oils? Example 2: I know of at least one maker (there may be others) who fills with 0W-40, but specs 0W/5W/10W-30. If the engine operated best on 20wt (sheared 30wt), why factory fill it with 0W-40 full syn? So here's my view: All the departments work towards the best engine possible while working under the constraint of "low cost." Usually R&D comes up with their favorite design in terms of performance, materials & tolerances. Then Manufacturing steps in & requires modifications to ease manufacturability & assembly (what may be best for performance & durability may not be best for build time & cost). Meanwhile, Management mentions that government is offering to save the company hundreds of millions of dollars in reduced fees if certain criteria (which have nothing to do with performance, durability, manufacturability or assembly) are met. Oil is simply one of these factors. Your engine might offer the best performance & durability using one thing, but other factors dictate something else. You market your product with the oil (& tires, & seat covers, & ...) which allows you to keep your fees low & that the natives will accept, but won't overtly sacrifice performance & durability.
 
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opps, I messed up I ment low tolerance Japanese manufactures use low tolerances. Also it takes more horse power to pump thicker oil so it's more noticeable in a smaller engine.like on a big v8 when the a\c is turned on, hardly noticeable, on a small 4 cyl very noticeable.
 
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Yep, give it a few days. Sometimes I feel like changing the radio station affects engine output. [Smile] Pat, just curious, do you get "winter formulation" gasoline up there?
 
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quote:
Originally posted by OneQuartLow: Yep, give it a few days. Sometimes I feel like changing the radio station affects engine output. [Smile] Pat, just curious, do you get "winter formulation" gasoline up there?
We definitely do. Doesn't seem to affect my fuel economy though.. [Smile] Yeah, this might be in my head.. plus today is pretty humid compared to the last few days.. I just hope the 0w40 holds up a lot better than the 10w30 did. [Dummy!]
 
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Re: winter formulation gas: Since I've owned my car, it's always gotten its best mpg in early spring, when the temps have warmed to the 60-80 F range, & (I suspect) winter formula(higher volatility) gas is still being sold. This all comes to a screeching halt usually sometime in late April to mid May. I can tell when they've gone to the full summer formula(lower volatility), gas mileage drops like a switch was thrown, & stays there or worse until the fall. I buy virtually all my gas at the same station: same pump, same parking position. Has anyone else noticed this?
 

Patman

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The winter formulation of gas doesn't seem to affect my cars MPG either, only the cold weather does. You can instantly see it go back up to higher levels if we get a warm week in February, even though the winter formula for gas is still being sold.
 
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JHZR2, I have a 99 ZR2, used 10w/30 up until about 50K miles. I swap out a qt of 10w/30 for a qt of 20w/50 now (and will not go any thinner even during the winter. I'm at 65 k miles now. Maybe you have to deal with colder winters than I do .. I check fuel mileage every tank and my mileage is not affected by using (slightly) thicker oil (normal fluctuations do happen given types of driving and time of year), but I can not tell any differrence just do to changing oil wt. Rando
 
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I agree, different oils will behave differently. M-1 may not have left as much deposits as BMW's (Castrol) synthetic but, the point being I used a 30 weight in place of the recommended 40 and 50 weights for the temperature range which caused (over the long term) increased burn off, volatility and eventual sludge build up. What does M-1 5-30 do? Burn like mad...maybe it goes out the exhaust instead. BMW's Synth. had less burn off at the expense of engine contamination...it was coking the inside of the engine. I agree with some of the other observations...why M-1 0-40 only in AMG models? The 'standard' M-Benzes don't get M-1. Why 10-60 E.U. Castrol only in the M cars? Why not the standard run-of-the-mill, dime-a-dozen 3 series BMW's?
 
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For what it's worth yesterday I put in M1 0w40 in my 2000 Prelude. Up to now;, 50,000miles I used M1 5w and 10w30. I don't know if it's psychological but the engine does feel a little 'sluggish', it doesn't seem to rev up as easily. Of course it could be just me... [I dont know]
 

Patman

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Originally posted by Quick_lude: For what it's worth yesterday I put in M1 0w40 in my 2000 Prelude. Up to now;, 50,000miles I used M1 5w and 10w30. I don't know if it's psychological but the engine does feel a little 'sluggish', it doesn't seem to rev up as easily. Of course it could be just me... [I dont know]
It could also be our warmer weather here too. Keep in mind you've probably lost 5% of your horsepower in this weather compared to a week ago when we were hitting record lows.
 

mdv

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quote:
Originally posted by Dr. T: [QBWhy 10-60 E.U. Castrol only in the M cars? Why not the standard run-of-the-mill, dime-a-dozen 3 series BMW's? [/QB]
I think the fact that the engines are completely different and have different tolerances has something to do with it.
 
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Greg My thinking is along the lines of yours, especially with the fairly recent 5W-20 recommendations. I also agree that oil shears, and while I don't think a 30 wt oil shearing down to a 20 wt will cause any problems, I do think a 20 wt shearing down to a 10 wt is very troublesome. a 10 wt oil is just too thin to sufficiently protect an engine. Some people claim using 5W-20 is the right thing to do simply because the manufacturer recommends it. As you stated, what the man. recommends isn't always the best thing for your engine. Most man. also recommend changing your oil every 7,500 miles, even when using dino, when even the majority of the oil buying public knows there isn't a dino that's good for that long. I believe the 5W-20 recommendation was made for reasons other than what's best for your engine. [ March 18, 2003, 11:02 PM: Message edited by: bottgers ]
 

Patman

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quote:
Originally posted by bottgers: Greg My thinking is along the lines of yours, especially with the fairly recent 5W-20 recommendations. I also agree that oil shears, and while I don't think a 30 wt oil shearing down to a 20 wt will cause any problems, I do think a 20 wt shearing down to a 10 wt is very troublesome. a 10 wt oil is just too thin to sufficiently protect an engine.
We have yet to see any 5w20 thinning down significantly like that, and I doubt we will. It is much easier to build a 5w20 that stays in grade than a 5w30.
 
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