have engine tolerances really changed

[philipp10]

I don't believe modern oils have contributed much to recent gains in engine life. It is the fuel injections systems that did that. I distinctly remember when fuel injection came on cars as the point when oil burners became extinct. Right around 1985-1988 period it all changed.

I'll bet anything you could run 1970's oils in odern cars and see very little change in engine life. Of course, JMO.

 

[Trav]

Thin oil can creep into places faster than thick oil is just a myth. Cold 0w20 is still thicker than hot 10w60.
I suggest you do some research about block and crank rigidity, block webbing, crankshaft metallurgy/surface finishing and oil pump design. That's where you will find the answers.

Crankshaft flex (the lack of), surface finish and oil pump design play a much larger role in the engines ability to run thinner oils.
It doesn’t mean you have to run thin oils in them it only means you can without the engine pounding its bearings out.

 

[philipp10]

Originally Posted By: benjy
todays manufacturing is both faster + more exact for sure! i am not a sure but wonder even on CNC machined parts if the cutters wear does the machine compensate for this. makes you wonder where the USA pushes thinner oils for mpg some of the same exact cars sold in europe spec heavier oils, i smell a rat!!! a few mpg VS a longer lasting engine i think!!! unless ALL the parts are made "in house" NOT globally there is still room for error. look at the recalls these days, cheaper parts from the lowest bidder cause problems, even some high $$$$ models have issues so unless an engine is "bluprinted" hand built + all clearances checked there will always be variations + expect more with low $$$ cars even today, car manufacturers are too GREEDY always looking for more profits!!!


Well in theory, whether parts are made "in house" or not should not matter. The detail drawing rules. Either the parts are in tolerance, or they are not.

 

[Merkava_4]

Originally Posted By: SandCastle
Tolerance refers to the variation of the characteristic.


I'm not sure I understand your definition. Tolerance is the allowed parameter of a clearance. You can still have a clearance that's out of tolerance.

 

[supton]

Originally Posted By: benjy
makes you wonder where the USA pushes thinner oils for mpg some of the same exact cars sold in europe spec heavier oils, i smell a rat!!! a few mpg VS a longer lasting engine i think!!!


Last I knew, average vehicle age was higher, and with more miles, than the Euro fleet. Europeans also have had long OCI's for a longer time than we have.

 

[DoubleWasp]

Being in the marine business, I can tell you for a fact that the exact same engines that GM put in cars and trucks with 5w30 on the oil caps are being run everyday with 25/40, 20/50, 15/40, and 25/50 in them with no penalties.

I've used thin oils in my trucks, under severe service, on extremely extended OCI'S without an issue, but I'd hardly call them necessary for specification. Newer engines can get away with it and do well. Some Euros are running a 60wt in our modern Era, some American cars come with 50wt or spec it for track use, so clearly not outdated yet.

 

[KrisZ]

Originally Posted By: Trav
Crankshaft flex (the lack of), surface finish and oil pump design play a much larger role in the engines ability to run thinner oils.
It doesn’t mean you have to run thin oils in them it only means you can without the engine pounding its bearings out.


Amen.

I remember watching a youtube video several years ago of a guy disassembling Toyota Prius, gen 1 I think, engine and commenting how its bottom end was built like a sports car engine and how well supported the crankshaft was.

I don't know how the "modern engine have tighter tolerances (confused for clearances) than ever" myth got started, but it explains why people are afraid for running thicker than specked oils, thinking it will damage something.

 

[BreakerBreaker]

Originally Posted By: TFB1
Originally Posted By: BreakerBreaker
Originally Posted By: zeng
Manufacturing tolerance range has been tightened for the past 30 years or so.
Tighter tolerance, if any, is more of consequential ..


This another reason why thicker oil is like a dinosaur, most the time, IMO - The thinner oil flows in those smaller galleys and such better than the thick stuff that feels nice and flows fine when warm or full hot, but, that's ot.

Who has ever said the oil galleys are now smaller?? If galley size was so critical a 5W-20 had to be used to insure adequate lubrication, the bearings would oil starve at temps below freezing...



That is a good point, I can only counter by saying that many manufacturers do in fact now say that a 5W-20 or 0W-20 (?) "has" to be used, as you say.

 

[DoubleWasp]

The question remaining, does it "have" to be used because that is the engine oil used when EPA does its CAFE testing, or a mechanical reason?

Knowing how the EPA works, I'm confident there is some sort of clause in there that prevents them from testing with a thin oil, and then recommending or allowing thicker oils in the manual.

 

[BreakerBreaker]

Originally Posted By: DoubleWasp
The question remaining, does it "have" to be used because that is the engine oil used when EPA does its CAFE testing, or a mechanical reason?

Knowing how the EPA works, I'm confident there is some sort of clause in there that prevents them from testing with a thin oil, and then recommending or allowing thicker oils in the manual.


The EPA does CAFE testing?

I agree they meddle with things, but the manufacturer should know the best. I have debated family members about this very thing. Some say, the manufacturers spec what they spec for fuel economy only, but that it is not the right oil to be used. Others, including here, call that nonsense, and that manufacturer would not say that if it would harm the car. Flip a coin, I suppose.

I suppose I should say that good flow is generally preferred in all things (uh oh) and that it was never said that oil galleys or channels got smaller. Though I Notice that many, many new engines want thin stuff in there. Perhaps I summised a correlation. If it helps though, beyond that, I will say I was wrong.

 

[440Magnum]

Originally Posted By: sciphi
Yes, they have.

As an example, GM got the cylinder dimensions precise enough on the 1.4T engines going into the Cruze that they could safely pick out random piston assemblies and be sure they'd fit.


That's tolerance, or variability. The absolute CLEARANCES in engines are a different matter, and I assume that's more what the original poster was talking about.

The design clearances for things like bearing journal gap are almost totally unchanged since WAY back, probably the 60s. Piston skirt-to-wall cold assembly clearances are tighter on engines built with hypereutectic pistons, but that's a bit misleading because the clearances actually wind up in about the same place once the piston reaches operating temperature.

But the scatter or spread or tolerance (whatever you want to call it- its the allowed variation among parts that before a part is rejected) has really tightened up a lot. In other words, the engine you buy is in all probability a lot closer to what the engineers intended than it was in 1970, or even 2000, even though the engineers are still aiming for almost exactly the same target. They knew what the ideal clearances were way, way back, but the ability of mass production to hit those ideals took a long time to catch up.

 

[Oldmoparguy1]

The single thing that contributed most to todays engines, was the elimination of lead (TEL). The metallurgy changes required to run unleaded gas was a major cause of doubling the life of an auto engine. In the 50's my dad's Chevy was wore out at 60K miles. By the 70's an engine was worn out at 100K. Now most engines will go 200K, and many over 300K. Todays engines are a marvel of engineering.

 

[DoubleWasp]

From http://www3.epa.gov/fueleconomy/

Quote:
EPA’s Fuel Economy pages provide information on current standards and how federal agencies work to enforce those laws, testing for national Corporate Average Fuel Economy or CAFE standards, and what you can do to reduce your own vehicle emissions.


My theory is a little different. That thin oil may not harm the engine, but that thicker oils are not recommended, or maybe can't be recommended because they were not a part of the CAFE fuel economy testing. Manufacturers may not want to get involved in recommending other oil specs for fear that they could be accused of VW-style cheating by using a thin oil for fuel economy testing, and then recommending a thicker oil that could be cast as using more fuel than their CAFE statistics.

 

[TFB1]

I ought to be common sense that if a engine's MPG is certified using a 0/5W-20 and another oil that is proven to give less MPG(even if only .1)is now recommended the [censored] will hit the fan..

 

[Nate1979]

It wasn't that long ago that it was common for OM to have different oil viscosity recommendations for different conditions - both temperature and load. These cars were still EPA rated for MPG and under CAFE. Even my 2010 Subaru allowed multiple oil grades.

 

[edhackett]

Originally Posted By: DoubleWasp
The question remaining, does it "have" to be used because that is the engine oil used when EPA does its CAFE testing, or a mechanical reason?

Knowing how the EPA works, I'm confident there is some sort of clause in there that prevents them from testing with a thin oil, and then recommending or allowing thicker oils in the manual.

It's for regulatory reasons. Here's a document that lays out what is required of the manufacturer.
https://www.ilma.org/advocacy/letters/gf4letter.pdf
Quote:

1. Owner’s Manual Language. The manufacturer provides instructions in the Owner’s Manual that clearly and unambiguously identify that GF-4 engine oil (identified by the presence of the American Petroleum Institute (API) “Starburst” logo) of a specific viscosity grade ( 5W20, 5W30, 10W30) is to be used in the vehicle’s engine under normal ambient temperature and driving conditions. If the API starburst logo is used in the owner’s manual in lieu of reference to GF-4, the manufacturer should include a brief explanation of its meaning. If the Owner’s Manual employs a graphical depiction of oil viscosity vs an ambient temperature range, inclusion of any qualifier word, “preferred” for example, associated with the oil viscosity is considered to introduce ambiguity into the instruction, and disqualifies the use of GF-4 engine oil in test vehicles. It continues to be appropriate for a manufacturer to specify the use of a lower viscosity grade in extremely low ambient temperatures where the normally specified oil may not flow adequately. If a vehicle owner wishes to use a synthetic, or partial synthetic oil, EPA does not expect a vehicle manufacturer to preclude use of such an oil if it meets all vehicle manufacturer requirements.
2. Labeling the Oil Filler Cap. The manufacturer clearly indicates on the engine oil filler cap, by label or other permanently attached means, that oil of a specific viscosity grade (e.g. 5W30) is to be used in the engine. Alternatively, affixing a permanent easily visible label underhood is also acceptable.


Ed

 

[Silk]

One big difference is piston rings - old engines used thick rings, and a basic oil ring...some had an oil control ring above the gudgeon pin, and another below it. They let oil and blowby past and wore out bores.

 

[CT8]

Originally Posted By: Silk
One big difference is piston rings - old engines used thick rings, and a basic oil ring...some had an oil control ring above the gudgeon pin, and another below it. They let oil and blowby past and wore out bores.
The top piston rings are also closer to the top of the pistons to lower HCs.

 

[CT8]

Originally Posted By: Trav
Thin oil can creep into places faster than thick oil is just a myth. Cold 0w20 is still thicker than hot 10w60.
I suggest you do some research about block and crank rigidity, block webbing, crankshaft metallurgy/surface finishing and oil pump design. That's where you will find the answers.

Crankshaft flex (the lack of), surface finish and oil pump design play a much larger role in the engines ability to run thinner oils.
It doesn’t mean you have to run thin oils in them it only means you can without the engine pounding its bearings out.
The computer controlled spark with the knock sensors keep errant cylinder from spark knocking it self to death. Yes there is so much to the light wieght high output, long lived, high MPG engines in todays cars.

 

[rodinator1234]

The machines that make machines are much more accurate than they were even 20 years ago. CNC machines make other CNC machines they compensate for tool wear as well as wear on screws and pivot point, it's incredible the capability of modern CNC machines. There is not any factor that is not compensated for in modern manufacturing processes.