Will Thinner Oils Damage Your Engine?

[ARCOgraphite]

I have posted on here several times over the years about the use of straight 20 weight oils in pickups. When I was in grad school at the University of Illinois from 1969-1973, almost all the pickup truck owners I knew out there ran straight 20 weight oil year round. Those trucks ran into the 150,000 mile range regularly with no noticeable oil related engine problems. And they were NOT designed for that weight oil.So I always have to smile when I read posts like this.. No, they won't. I use 0W-20 VW 508 oil in my 2019 Passat and get great mileage and drive-ability.

I tried costly Mobil 1 in the early 80's in my S10 V6 pickup. Unfortunately, I had to take it out after one trip around the block. The engine made so much clanking and clacking noise, it thought it was ruined. I put a 10W30 Valvoline back in and all was proper again. Smooth and powerful.
A straight 20 likely has a higher HTHS than a 20W20 or an EC rated 5W30. So, under stress, the 20 will provide equal film strength to the 5W30 and also have the benefit to not contribute varnishing from oxidised VM adds.

 

[ARCOgraphite]

I’m sure Mobil paid him a nice amount for that advertisement.

Todays modern engines hardly work at all in normal driving running at 1500-2000 rpms for the most part.

I know! I feel bad My 1973 LTD was working overtime with the 429 spinning at 1200.

 

[PimTac]

I know! I feel bad My 1973 LTD was working overtime with the 429 spinning at 1200.

Those “Long Time Devils” had a habit of getting back at you somehow. I knew someone who had one, a bit newer I think. It was constantly being worked on.

 

[OppositeLocK]

I say no. As the question is phrased, thinner oils will not damage your engine.

Going one step further, thinner oils should and will not cause increased wear in engines with specs saying to run those oils. If a manufacturer takes a engine that was originally running on 5w30 ( a CAFE oil itself) and back specs it to 0w20 without any changes then one might ponder that.

Many of the modern engines these days run on 0w20 very well as they were designed with that grade in mind.

CAFE has been around now for almost half a century. That is longer than BITOG has been in existence. It is the eternal argument here.

But don't some manufacturers do exactly just that? Different regions have different oil specs and it usually has to do with environmental regulations.

 

[ARCOgraphite]

Those “Long Time Devils” had a habit of getting back at you somehow. I knew someone who had one, a bit newer I think. It was constantly being worked on.

I am a GM guy - but this one dealer in the Lowell, Mass. area had advertised a" Red Tag Special weekend" to blow out trades "as is" that would normally go to auction.
Looking for a Winter beater, my buddy and I found two LTD's. They were former Sherriff and Chief cars with about 100K on them. Pretty clean, no rust well serviced - though the one I picked had a sizeable dent in the rear quarter. They both had the wonderful 429 4V and Certified speedo and plain bench seats. I don't know why but mine didn't have a Traction-Lok rear axle. But just $700- out the door.

Never had much a problem with those beasts, except one day my engine quit on the way down a hill to my GF's house. I rolled in her driveway.
To her dismay, I wanted to work on the car immediately - and after some quick "spark and fuel" checks I found it had no spark. So I went to check the points. I bumped the ignition over but the rotor wasn't moving!. To make a long story short, I pulled the distributor and the drive gear had sheared the roll pin locating it. On these cars the dist shaft spins the oil pump. NO moving dist no oil pressure no engine run.
The oil pump was jammed with something. I was able to rock it back and forth and get it spinning again, then I put the thing together. I used a common nail for a roll pin substitute to get home. Later when I dropped the pan,, I found a bunch of plastic parts in there that ended up being valve seals that had hardened up and flaked off. Somehow they got past the oil pickup screen and filter.

Must have been all that cop car idling.

 

[PimTac]

But don't some manufacturers do exactly just that? Different regions have different oil specs and it usually has to do with environmental regulations.

Yes they do and one reason was availability of 20 grade oils. Australia is a example used here quite often as a reason to confirm the bias that the individuals want to run a thicker grade. Now, 0w20 oils are in supply in Australia and some vehicles are running that per spec.

A lot of this back and forth is confirmation bias or misunderstanding of the capability of 20 grade oils in suitable engines.

 

[ABN_CBT_ENGR]

But don't some manufacturers do exactly just that? Different regions have different oil specs and it usually has to do with environmental regulations.

Let me tell you something else that "can" happen but without access to the exact design requirements ( heavily guarded IP) we may never know for sure.

You can have a case where there is a base design and the company directs a "tweener" solution for various conditions where they may open a range of acceptable lubricants but to maintain mechanical integrity they may open a tolerance to a high end rather than a median and possibly change a surface finish or a different heat treat to make up the difference.

I suspect this probably happens a lot with cars more so than industrial equipment as they have different and various requirements to meet all over the world.

This would be hard to define and detect because its not an engineering requirement based on an actual equipment requirement or mechanical integrity issue but a management directed change for other reasons.

Don't be surprised to see this happen a lot

 

[MaDMaXX]

...

You can have a case where there is a base design and the company directs a "tweener" solution for various conditions where they may open a range of acceptable lubricants but to maintain mechanical integrity they may open a tolerance to a high end rather than a median and possibly change a surface finish or a different heat treat to make up the difference.

...

To be more clear, are you saying in some cases the manufacturer might spec a thicker grade oil to cover themselves?

 

[ABN_CBT_ENGR]

To be more clear, are you saying in some cases the manufacturer might spec a thicker grade oil to cover themselves?

I wouldn't say "cover"- I would say open a tolerance range to accommodate several different regions with a minimum of additional costs based on the design knowing that if the vehicle is used out of design range or modified, it might require lubrication modification as well

 

[benjy]

reading about the importance if quality oil filters on machinery lubrication it was NOTED thinner oils at running temp provide LESS protection as "dirt" in the oil can be the same size as the thinner oil film of 20W's unless your running a bypass system. typical better filters catch some smaller particles but not all + these are said to cause the most wear!!! a poor trade off for a 1/4 mpg IMO!!

 

[MaDMaXX]

I wouldn't say "cover"- I would say open a tolerance range to accommodate several different regions with a minimum of additional costs based on the design knowing that if the vehicle is used out of design range or modified, it might require lubrication modification as well

So, let's say a manu spec'd 5w20, based on what you're saying, they might have been ok with a 5w10 (for example) but said 5w20 instead?

 

[ABN_CBT_ENGR]

So, let's say a manu spec'd 5w20, based on what you're saying, they might have been ok with a 5w10 (for example) but said 5w20 instead?

Yes, very possible and quite probable- it would be impossible to state for certain without key design information but this is common in other types of equipment. I would be surprised if auto manufacturers didn't do the same thing.

 

[MaDMaXX]

Alright so it's as possible for them to also spec what generally, or, mostly fits, ie. the 5w20, should their testing show that a high enough percentage shows ok?

 

[kschachn]

Alright so it's as possible for them to also spec what generally, or, mostly fits, ie. the 5w20, should their testing show that a high enough percentage shows ok?

Of course, it’s what Honda terms “acceptable“. Given the multiple competing demand requirements on the design, the use of the oil gives acceptable wear.

 

[ZeeOSix]

Ford specs adjustments referred to 5w 20 pcmo for belt driven cams . 5w 30 pcmo for chain driven cams per my friends in Dearborn

Guess those in Dearborn don't consider the Coyote (which has timing chains galore and specs 5W-20 in CAFE driven USA) when they spec 5W-30 for vehicles.

 

[ZeeOSix]

Going one step further, thinner oils should and will not cause increased wear in engines with specs saying to run those oils.

Just because a thinner oil is specified for the engine doesn't mean it's giving the same level of wear protection as a thicker oil. The most basic result of tribology research shows that MOFT is a direct function of the oil viscosity, and MOFT increases with viscosity. In non-CAFE countries where the same US manufactured engines are used, they typically spec a little thicker oil and/or show them as optional in the owner's manual.

CAFE is the main driver of thinner and thinner motor oils specified for use in the USA.

 

[ABN_CBT_ENGR]

Z's answer is essentially correct on the protection but lets explain it with an analogous example as people may not be able to relate to it.

Lets say you have an engine designed for 50 HP @ 100RPM with a bng clearance of .004" and a lube system giving 50gpm@50PSI .

You do the 'secret stuff" ( metallurgy, heat treatment, poisons wedge and all that) and determine it takes 20 MOFT units ( yes that's a made up measurement for illustration purposes)

That's the design spec and all that's hard built into the engine and cant be changed without physical modification.

So, a 20 oil gives 23 units, a 30 gives 27 and a 50 gives say 32 units of MOFT.

The OEM decides the baseline spec will be 30 ( picks mid range based on his design performance standards which is ALL he is married to)

So within tolerance you can change that with varying levels of MOFT change but within acceptable limits so you are OK (ish)

Now you operate it differently ( lets say now you are getting 70 hp @ 175 RPM) but didn't change everything else

You may find the original recommendations inadequate or whatever you change to isn't all you need.

That's why this is not a direct linear answer because multiple things go into what the necessary MOFT has to be and multiple factors affect what has to be changed to maintain it the further you get from the OEM design range.

Some of this is IP so you have to guess or experiment.

 

[tig1]

My family has four Fords with the Duratech 4 cyl engines. I had another one (2007 Focus with 175k when totaled). At present we have logged some 877K(miles) on them with M1 20 wt. oils. OCIs 10K. To date no internal engine problems including timing chains or guides. Also all engines are very clean, and show no signs of engine wear.

 

[RDY4WAR]

My family has four Fords with the Duratech 4 cyl engines. I had another one (2007 Focus with 175k when totaled). At present we have logged some 877K(miles) on them with M1 20 wt. oils. OCIs 10K. To date no internal engine problems including timing chains or guides. Also all engines are very clean, and show no signs of engine wear.

I had a 2007 Focus also that I turbocharged and beat the snot out of. I stuck with 5w-20 oil. It never gave me an issue. It took everything I threw at it.

 

[xyxptlx]

So I select the metallurgy, dimensions, finishes, treatments to achieve this. ( second step is to build it)

How is the oil system itself accounted for? Flow rates, for example. What if anything can account for the finish in oil passages with sand cast? Are they just over sized or machined? I would guess they are sized for a viscosity range. Do the oil holes for rods or mains act as orifices, that is, is cavitation a consideration?