Originally Posted By: MarkStock
OVERK1LL - this point that you make I've never disagreed with in principle. Take the same oils except with different HTHSV, take the same engines, and the lower HTHSV oil gives you less headroom. Simple principle.
Yes, except the minute you change the HTHS viscosity, they are no longer the same oils
HTHS is a fundamental component as to how an oil behaves in an engine relative to the bearings and subsequently, altering the HTHS viscosity, alters the oil's behaviour.
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I can't argue about what is enough headroom because I don't have the data that matters.
I don't know what the exact figure is for the engines in question, but Ford obviously does and subsequently limited power output at a level that still provides some (headroom). That being said, it is going to vary significantly between engines and engine families because the components that are effected the most by HTHS are the bearings.
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I do see that min HTHSV in German cars is 3.5. That's very high compared to 2.6.
Yes, and again, we've hashed this out before and this is due to oil temperatures that would be seen on the track or during high speed autobahn use. They do not necessary apply to North America. However, the engine would have been designed and tested with these lubricants and these lubricants will also be engineered to perform properly under the Euro-spec extended drains, so the manufacturers are married to their certifications and they aren't going to come out with a certification just for the North American crowd, because what if Joe takes his AMG to the speedway and spins a rod bearing because the American-spec oil wasn't up to the task?
Subsequently the Euro marques "make it easy" by demanding that you use a lubricant that meets their (stringent) specifications that do factor in Autobahn use.... Even if your car will never see it.
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But on the other hand I see the Japanese, whose engineering I respect the most, pushing down even lower.
1. Japan doesn't have an Autobahn.
2. Roads in Japan do not see the same sort of high speeds as are sustained in Germany.
3. Based on #1 and #2, it is completely worthless to compare what the Japanese spec "in general" from the Germans, because the cars are NOT designed for the same purpose.
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I see talk about lower friction engines and exotic oil that means the lighter oils have to be synthetic. Surely the headroom must have improved through engineering developments. Surely HTHSV of 2.6 in 2012 is not the same headroom as HTHSV of 2.6 in 1992.
Shannow covered this extensively recently when he talked about bearing SIZE in relation to the reduction viscosity and the Japanese in particular changing the size of their bearings to accommodate the use of these super thin oils.
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I also see the Japanese attaining engine efficiency through things like less friction, more precision, whereas the Germans are going the route of smaller engines with turbos. The former is an approach that generates less heat, the latter an approach that generates more heat.
Nissan, Subaru, Honda (RDX), Toyota, Mazda...etc have all made and continue to make turbcharged engines. I don't know where you are looking here?
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Just as the Germans realized their engine designs needed a certain amount of headroom, I think the Japanese also understand the headroom they need.
Yes, which is why Japanese cars like the Nissan GT-R spec 0w40
The Honda S2000 spec'd 10w30 or 5w40, the Lexus IS-F requires 5w30....etc
So even the Japanese step it up a notch or two when power density is increased and the potential usage profile steps outside of the grocery getter range.
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Now, onto the point of my post. It wasn't about Headroom!
It was about the assertion that it is impossible that one oil fits all.
My point was that Mercedes believes one oil does fit all. In every country, in almost every engine from 1.5L to 6.5L Black Series, M1 0w40 is the recommended oil. This suggests it's viscosity is appropriate for everyone in every operating condition. Grocery getter in mild England to autobahn blaster.
The difference you are seeing is that the Euro marques aren't saying one OIL, or even one VISCOSITY fits all. They are saying one certification, or set of certifications will properly protect the engine regardless of where it is operated. The grade is irrelevant as Trav pointed out, as many of the oils that meet many of the Euro spec's are 0w30, 5w30, 0w40, 5w40..etc. But they meet the spec's for the manufacturer in terms of extended drain capability, engine protection and cleanliness.
