How does HTHS viscosity impact engine performance? 

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I have two vehicles, both of which are around 70k miles, both maintained very well, and both recently developed some timing chain jiggle/tick around the same time with the only variable having been that I've been purchasing the latest motor-oil formulations which are constantly being updated to be more "fuel efficient". I should note that all of the motor oils I've been using are full synthetic. I spent a good while trying to figure out why both of my vehicles would suddenly develop timing chain noise (not just at start-up but a constant jiggle/tick indicating stretching due to wear) when that shouldn't be the case yet since each vehicle is just over the 70k mark. I tried experimenting with additing viscosity improvers with some success noting that the VI's would definitely quiet things down for a bit although ultimately as that batch of motor oil would accumulate miles the timing chain noises would return but also I noticed that even if I could quiet the timing chain noises (via viscosity additives) that on hot days or once the engine/oil got hot, the noises would pop up again, thus indicating that it was not strictly a viscosity or even lubrication issue, but rather a formulation issue in which the boundary layer was becoming compromised at high temperature. Some brands of motor oils were worse than others when it came to this high temperature reduced performance characteristics issue with Mobil-1 being the worst of all, and I tried 3 different versions of that brand with their highest fuel efficiency version resulting in so much valvetrain noise to the point that it was alarming and I dumped that oil after only about 50 miles of use. SuperTech was not nearly as bad but still required a viscosity improver additive reduce the chain jiggle noise but just as before, that was only partically effective at dealing with the chain noise and the noise would progressively increase and return as miles were put on the oil and/or the oil would get hot. Because of all of my observations and experimenting with different oil viscosities, brands, as well as viscosity additives, I came to the conclusion that the timing chain noise issue was due to premature wear that was occurring due to constant changes in motor oil formulations that were being pushed by never ending government regulations/requirements for increased MPG ratings and due to this compromises were being made that were allowing for greater wear to occur in the name of improved fuel economy. The thing is, new cars are being designed to "tolerate" these new "high effeciency" motor oils with tighter tolerances and design elements that takes these types of oils in to consideration, but that does not take in to account all of the older cars on the road such as mine that although they have low miles and are well maintained, they were designed to operate with motor oils formulations that were available at the time, and which oddly enough not appear to be superior to the new motor oil formulations when it comes to wear prevention and especially maintaining their metal to metal boundary layer even in the highest temperature and critical wear/contact areas of the engine. This is where I believe I've ended up with premature timing chain wear (ie "stretched" timing chains) as this issue crept up little by little as the newest generation of motor oils have hit the market. My latest attempt to test this and attempt to address the issue it has caused was to search out an older motor oil formulation/rating and then carefully observe the results. So I discontinued using the latest formulations and instead went with an older formulation (with an actual stated HTHS of 3.6) and from the very first crank of the engine, all timing chain noise is gone and even on hot days and at oil maximum temps the timing chain jiggle has not returned. I should also note that as far as motor oil viscosity goes, I've tried to maintain a certain degree of consistency when it comes to stated cSt viscosity numbers, more so than the actual xxW-weight number on the front of the bottle since there are for example some 5W-30 rated oils that have a cSt rating of between 11.6 to 12.4 while at the same time there are some 5W-40 motor oils which are nearly identical in the cSt with a stated rating of cSt of 12.6 at 100 C. (same can be said of 0W-20 versus 0W-30 oils, check the cSt @ 100 C rating) In my case the timing chain wear has unfortunately already been done due to the reduced protection that these most up-to-date motor oil formulations, thus the long term solution is going to be installing new timing chain kits in both vehicles WAY before either of them should have had the need of such. Using an older oil formulation though is buying me time to do such work since this previous generation of oil formulation seems to do a much better job at both maintaining it's viscosity and HTHS rating than the current formulations (which in turn is providing a "buffer" to my cars timing chains, taking up just enough space in between each link of the chain to prevent it contacting the chain guides) which in some cases are actually starting off with a lower HTHS to begin with but as my own experimenting has shown, even the ones that claim to still have an HTHS above 3.2 don't seem to be able to maintain those characteristics for very long. Thus staying away from the newest motor-oil formulations which may be fine for 2018+ designed engines but the compromises they have made with these new formulations are based on increasing MPG's and not on protecting critical wear components on previous generation engine designs.

Another fabulous explanation. Thanks LE….HTHS is the hot topic with regards to the new range of 0W-20 oils and ACEA low SAPS C5 and C6 oils

So thankful I found this channel!❤ Keep us educated pls😅

I only run oils with HTHS of 3.5 or greater in any vehicle I own. Do not let them convince you that reduced HTHS formulas are better. They don't even yield any fuel economy improvement. Stay away from anything under 3.5. The VW/Audi 504/507 or Porsche C30 C40 spec is the only one I use in anything. The government wants your car in the junk yard ASAP. Remember that.

I think that I would be willing to sacrifice a bit of fuel efficiency for higher protection! So I suppose I would need to look for oil with a higher HTHS.

Greaaaat

Do the tolerances an engine is built with affect the HTHS that you would need?

Is every diesel SUV a light diesel engine ? Also, will an A5/B5 offer enough wear protection for a high mileage diesel car ?

Obviously the experts have proven fuel savings by HTHS theory so another positive from the oil/chemical/OEM industries in their determined approach to emission reductions and fuel savings. A great presentation LE.

Went from a 5w30 to a 5w40 for the summer, mostly hiway driving..... no differance in the MPG.

So what base oils or additives are used to make up for lower HTHS?

I have 2 oils, same ester base, one is 5W50 18.5 cst@100 4.4hths other 10w50 19.5 19.5. St@100 5.2 hths. Is the latter simply better for track days and spirited driving in Porsche 944 in summer, or it's not that simple.

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my mazda skyactiv engine requires 0w20 have already driven 135,000 km and the engine still runs like new at the beginning I was skeptical about 0w20 but it works excellently the oil also has no oil consumption

If it so that with lower HTHS fuel efficiency is higher then why the engine oil has to hv a minimum HTHS requirement to fulfil. Is HTHS to do anything with wear of moving parts??? As a very low HTHS with high temperature and high shear the film may break as its having lower viscosity and there might be chances of direct contact of moving parts….

Unfortunately, modern oils often have less robust additive packages for emission system protection.

Does higher HTHS necessarily mean higher protection? There are myths surrounding the BMW S65 engine rod bearing, which people claimed that the rod bearing clearance is too tight for the 10w60 oil to pass through the gap. However I think it's the HTHS being too low, contributing to the damage of rod bearing. I suppose the temperature within the bearing should be way higher than 100C and will put enourmous stress on the oil, therefore I always opt for oil that has the highest HTHS with decent 40C and 100C viscosity. Do you think if I am on the right way? Thanks

A question: If my Acura J37 engine has a recommended oil grade of 5w-20, can 5w-30 oil be used instead? The reason is that 5w-20 seems to shear faster and then engine starts to consume oil at ~ 2k miles. I was thinking to get a thin 5w-30 spec oil(Pennzoil Platinum) which would slightly be thicker than a heavy 5w-20.

So if my car requires VW 508 and I put in a VW 504 oil in instead the ONLY negative is fuel economy? Or is it possible changes in certain systems start/stop tech, valve lift tech, different oil pump to accommodate the 508 oil switching to a 504 will not harm these systems in any way?

what is the relation between hths and the (high mid low) saps ?

% wise what is the difference from a 2.96 hths and a 3.5 hths?

Can low HTHS oils be used in diesel engines even though they are labeled as "Gasoline Engine Oil"? The question comes from researching for A5/B5 oil for a Ford Ranger L6 diesel engine (not available in the USA) Amsoil's Signature Series 5W30 is one of the best oils with this ACEA spec and I'm in doubt if I should ignore the label since "gasoline engine oil" means nothing. 15ppm diesel is the norm here btw.

IMHO the importance & modern day relevance of HTHS is massively overstated. It's the lubricant equivalent of Visible Pantie Line; something for the naturally neurotic to stress about but which isn't really that big a deal...