Running thinner oil, is my reasoning skewed?

Thanks. The experiment won't go further however. I knew it would be okay because tons of cars with the same engine are running something like an ILSAC 5/10W30 in north america, some with very high mileage and i've seen similar or better UOAs on Mercedes forums compared to Mobil 1 0W40. I just wanted to see by myself what i keep hearing on bitog about improved gas mileage and better throttle response. It definitely seems less sluggish when cold. I'll probably go back to a 40 anyway after a short OCI. This oil cost me next to nothing anyway... The question was also for me to find out what in these engine would require a higher HTHS compared to a similar japanese or american engine and i still don't find anything at all.
A UOA is not a proxy for wear and there are many things that can impact what you see on it. An oil with esters in the base oil blend will have a tendency to chelate, increasing concentrations of what you see for metals in the analysis, but may, in application, actually have lower wear. This is why tear-down testing is mandated as part of the approval process, where physical measurements are taken.

Design choices (bearing width, materials selection, use of coatings, valvetrain design, intended operating profile...etc) there are myriad contributors to OE oil grade selection and why one might mandate a minimum HTHS of 3.5cP while another engine that might appear similar on paper can get away with 2.9cP instead.

When Honda was looking at going "super thin", their language was not about the these thinner lubricants improving anything other than fuel economy, simply that "acceptable" wear would be assured through additive chemistry as the operating profiles for components that were previous in hydrodynamic or mixed, transitioned to mixed or boundary (metal on metal) and how wear would be controlled under these circumstances. It was also determined that bearing width needed to be increased as the HTHS dropped below ~2.5-2.6cP (the minimum for an xW-20, which they had previous been designing for) and novel coatings were required on other parts of the engine.

The OEM's have, and are, putting significant R&D dollars into engineering, or in some cases, re-engineering, engines and components to remain durable and attain acceptable operating lifespans on thinner lubricants, because the increase in fuel economy makes this worthwhile, particularly with government regulation. These are not decisions being made arbitrarily with respect to just spec'ing something thinner for existing designs at this juncture.

If we look back at Ford's transition from the ~2.9-3.1cP HTHS 5w-30 recommendation to the ~2.6cP HTHS 5w-20 one, this involved extensive in-house testing, and some engines were never back-spec'd because the results weren't acceptable. That ~2.5-2.6cP HTHS for an xW-20 seems to have been the floor for a lot of existing designs that were originally spec'd for an ILSAC/GF-x API xW-30 with the higher HTHS of ~3.0cP. Going below that required significant changes, so much so, that the thinner oils (0w-16, 0w-12, 0w-8) were given their own ILSAC category so that it was more obvious that these wouldn't be appropriate for non-spec applications that didn't explicitly call-out these grades.
 
Thanks OVERKILL. In the end it seems like the better choice for me would be a MB229.5 5W30. I would still have the improved throttle response and possibly fuel economy when cold for this wimpy engine and i would be sure to reach high mileage without compromising reliability at all. However, most 5W30 are 229.51. Still not sure if it is optimal to run in a gas engine.
 
Thanks OVERKILL. In the end it seems like the better choice for me would be a MB229.5 5W30. I would still have the improved throttle response and possibly fuel economy when cold for this wimpy engine and i would be sure to reach high mileage without compromising reliability at all. However, most 5W30 are 229.51. Still not sure if it is optimal to run in a gas engine.
or 229.5 0w-30 instead, if you can find one like Ravenol SSO:
Screen Shot 2022-02-27 at 3.09.27 PM.png

Screen Shot 2022-02-27 at 3.09.41 PM.png
 
Driven is race oil. The bearings have other considerations, width and diameter of bearing, expansion of bearings due to heating and loading with HP with the bearing clearance. Personally would go with the OM on viscosity, it is engineered for that viscosity. And personally would go with the lower recommended viscosity if given a choice... On one side HTHS and Noack is higher in higher viscosity, better cooling and more HP squeezed out in lower viscosity. Always a give and take.
 
Driven is race oil. The bearings have other considerations, width and diameter of bearing, expansion of bearings due to heating and loading with HP with the bearing clearance. Personally would go with the OM on viscosity, it is engineered for that viscosity. And personally would go with the lower recommended viscosity if given a choice... On one side HTHS and Noack is higher in higher viscosity, better cooling and more HP squeezed out in lower viscosity. Always a give and take.
The Euro marques are notorious for not spec'ing a viscosity but rather a "spec", which will have a range of viscosities associated with it, all of which are acceptable. The 0w-30 from Ravenol seems to be a pretty good fit and satisfies the OP's desire to run something on the lower end of the range allowed by the manufacturer while not actually deviating from spec.
 
This is a follow up to another thread i made a while back asking people about their experience running 0/5W20 in old engines.

I've been leaning towards thick oil since i know what oil is and only cared about xW40 ones. Probably because i'm european and have been told about the inevitable disasters that will happen if 5W30 is used in an engine because it's like water. I am more and more interested in experimenting with thinner oils in my application as i am learning about the possible benefits they can offer as well as how bearing clearances and oil pressure work. I've established that running a synthetic ressource conserving 5W30 is in my engine is in fact more than safe.

Here are the values found in the service manual for my engine:

Main bearing clearance: between .025 and .045mm = between .00098 and .00177 in inch.
Rod bearing clearance: between .030 and .050mm = between .00118 and .00197 in inch.

Mininum oil pressure at hot idle: .3 bar = 4.35 psi.
Minimum oil pressure at 3,000 rpm : 3 bar = 43.51 psi.

I've heard about the 10 psi per 1,000 rpm rule and from experience these engines run much higher pressure than that even if MB says 4.35 is acceptable at hot idle (that seems extremely low). The typical pressure is more like 1.5 bar (14.5 psi) at hot idle and the gauge usually pegs at 3 bar (43.5 psi) between 1,500 and 2,000 rpm when hot on all the M1xx gas and OM6xx diesel engines.

I've never been able to get my oil temp higher than 95c (203f) after an italian tune up but that was in winter and it seems to follow coolant temps most of the time, around 80c. It is safe to say that i will rarely encounter extreme oil temps. Most of my driving is very relaxed, mostly 2,500 rpm highway cruising and hypermiling.

I just came accross this chart on the Driven Oil catalog, i've circled what corresponds to my engine's bearing clearances and oil temps.

View attachment 90590
View attachment 90591

Driven XP10 = 0W10
Driven XP2 = 0W20

Here's the chart on my (somewhat outdated?) owner's manual: The requirement was MB229.1 or API SH if not available.

View attachment 90598

Conclusion: It seems evident than running a low HTHS 5W30 (A5/B5 or ILSAC) should be harmless year round in my application, theoretically even a 20 but that raises others questions and a few concerns about other things likes piston rings etc. Is my logic skewed? please chime in!

My GT500 specified 5W-50 and I ran the following:
Drag - M1 5W-30 (160F Oil Temp)
Street - M1 0W-40 (200F Oil Temp)
Track - M1 15W-50 (250F Oil Temp)

I'm not about to suggest what you run. It's up you to research your application and decide what you believe is ideal for your application.
 
.If we look back at Ford's transition from the ~2.9-3.1cP HTHS 5w-30 recommendation to the ~2.6cP HTHS 5w-20 one, this involved extensive in-house testing, and some engines were never back-spec'd because the results weren't acceptable. That ~2.5-2.6cP HTHS for an xW-20 seems to have been the floor for a lot of existing designs that were originally spec'd for an ILSAC/GF-x API xW-30 with the higher HTHS of ~3.0cP.
Ford bumped the recommended viscosity spec from 5W-20 to 5W-30 on the 2021+ Coyote. No engine changes on the 2021 Coyote, and not sure if Ford is back specing for the older Coyotes. A lot of 2015+ Mustang owners run 5W-30 over 5W-20 anyway.
 
Ford bumped the recommended viscosity spec from 5W-20 to 5W-30 on the 2021+ Coyote. No engine changes on the 2021 Coyote, and not sure if Ford is back specing for the older Coyotes. A lot of 2015+ Mustang owners run 5W-30 over 5W-20 anyway.
Good point, so it can go the other way as well.
 
Ford bumped the recommended viscosity spec from 5W-20 to 5W-30 on the 2021+ Coyote. No engine changes on the 2021 Coyote, and not sure if Ford is back specing for the older Coyotes. A lot of 2015+ Mustang owners run 5W-30 over 5W-20 anyway.

I'm not sure I wouldn't call all that cylinder deactivation crap on the F150 no changes. I believe the Mustang change was related to moving all 5.0 to 5W-30 and avoiding confusion. It was a fight to get the dealers to put 5W-50 in the '11-14 Track Pack instead of 5W-20 every time it was serviced. Of course what it does do is provide evidence that a heavier oil isn't going to hurt anything (although may not be needed) in most applications.
 
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Never too thin to be on the ragged edge of metal-to-metal contact in the journal bearings. MOFT and HTHS headroom to cover all possible driving conditions is a good thing.
Thanks, Z . Agree. I'm at 8.8 on my Camry and may slightly increase my vis toward 3.0 hths .
 
I'm not sure I wouldn't call all that cylinder deactivation crap on the F150 no changes. I believe the Mustang change was related to moving all 5.0 to 5W-30 and avoiding confusion. It was a fight to get the dealers to put 5W-50 in the '11-14 Track Pack instead of 5W-20 every time it was serviced. Of course what it does do is provide evidence that a heavier oil isn't going to hurt anything (although may not be needed) in most applications.
Yes, the Coyote in the F150 gets cylinder deactivation and the Mustang doesn't ... but I doubt Ford bumped the viscosity up to 5W-30 because of cylinder deactivation. I'll have to go look at the on-line Mustang owner's manuals on Ford's website to see if they updated them to back spec 5W-30 for previous years. The Mustang in Australia was speced for 5W-30 years ago.

Yes, plenty of evidence over the years that the Coyote can run anything from 5W-20 to 5W-50. Lots of guys run 5W-30 which seems to be ideal for street driven Mustangs.
 
Yes, the Coyote in the F150 gets cylinder deactivation and the Mustang doesn't ... but I doubt Ford bumped the viscosity up to 5W-30 because of cylinder deactivation. I'll have to go look at the on-line Mustang owner's manuals on Ford's website to see if they updated them to back spec 5W-30 for previous years. The Mustang in Australia was speced for 5W-30 years ago.

Yes, plenty of evidence over the years that the Coyote can run anything from 5W-20 to 5W-50. Lots of guys run 5W-30 which seems to be ideal for street driven Mustangs.

I ran 0W-40 in both the Track Pack and the Roush Supercharged Mustang for street use but then I also ran 15W-50 instead of 5W-50 for track use. The 5W-50 tends to shear to a 30 grade after use just like the M1 0w-40.
 
I ran 0W-40 in both the Track Pack and the Roush Supercharged Mustang for street use but then I also ran 15W-50 instead of 5W-50 for track use. The 5W-50 tends to shear to a 30 grade after use just like the M1 0w-40.
You actually have a UOA that shows a two-grade viscosity deviation due to mechanical shear?
 
You actually have a UOA that shows a two-grade viscosity deviation due to mechanical shear?

Seen it multiple times with 5W-50 Motorcraft. Sometimes as low as the high 11's. I don't think I've ever seen the others drop below the low 12's. I'm fairly certain you can find analysis posted on this site with sub-12.5 MC 5W-50. I've seen it a lot on the SVT boards.
 
Seen it multiple times with 5W-50 Motorcraft. Sometimes as low as the high 11's. I don't think I've ever seen the others drop below the low 12's. I'm fairly certain you can find analysis posted on this site with sub-12.5 MC 5W-50. I've seen it a lot on the SVT boards.
With GC run on them for fuel? Just would be interesting to see how much of that is fuel dilution.
 
With GC run on them for fuel? Just would be interesting to see how much of that is fuel dilution.

I don't remember a lot of fuel or especially low flash points (BS). The MC 5W-50 just seems really bad for shear. Some people claimed it was designed to do it like all the GF-1 5W-30 used to be. If that's the case why not just start out as a relatively thin 5W-40? Didn't make sense to me.
 
I don't remember a lot of fuel or especially low flash points (BS). The MC 5W-50 just seems really bad for shear. Some people claimed it was designed to do it like all the GF-1 5W-30 used to be. If that's the case why not just start out as a relatively thin 5W-40? Didn't make sense to me.
Flash point already has relatively poor repeatability and reproducibility even when properly tested. Then to extrapolate another value on top is dragging you out into the weeds.
 
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