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Originally Posted by rice_classic
Hydrodynamic wedge, that's why. Just like in the hydroplaning tire analogy from the other thread, we have a LOT more weight pushing down on the tire that's trying to hydroplane making harder for it to form a "wedge" of water in front of it allowing it to hydroplane (aka for lubrication to happen).
A stock FA20 (200hp) and a FI-FA20(400hp) elicit very different cylinder pressures and forces upon the oil, however their con-rod and crank journals stayed the same. So one needs to take into account the right oil viscosity needed to maintain that hydrodynamic wedge in the bearings that's needed to support the extra power of Forced Induction or the extra thinning (viscosity loss) from extra heat or both.
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that's the thing though, the keywords here are "right oil viscosity" otherwise we would be using 15w-50 oil and to me the sweet spot is 5w-30 (on the thicker side of course)
and the "extra heat", like I mentioned earlier 5w-30 seems to be running better on our engines with my experience(generates less heat compared to 0w-40 ..if the 5w-30 provides adequate pressure at the given temp range and there's not big of a difference between 10w-30 and 10w-40 (a couple psi differences) like in the Dezoris' chart I would still stick to the recommended viscosity range for the FA20 engines (definitely lower than 13 cst at 100C degrees)
I think I've found the same article and the analogy you were reffering to at the website called "marinediesels.info"
http://www.marinediesels.info/2_stro...ubrication.htm
they also added :
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Viscosity of the lubricant is an important feature. The higher the viscosity, the higher the friction between oil and shaft, but the thicker the hydrodynamic film
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at the end I understand your point on that analogy but without knowing the true effects on specific application (FA20) with some comparable data it's really hard to make any assumptions at this point IMO, even with the data in hand those assumptions may be misleading .. for instance say you build the best oil in the market and you claim it's 2x more protection and one make say for instance 0.01mm film thickness and the other is 0.02mm, that claim is holds true but the difference may be considered still negligible if we only need 0.001mm of thickness. ..all we know at this point is oil film thickness is adequate below 280F with Mobil 1 5w-30 and it's still within the manufacturer's recommended range ...if you have FA20 engine specific data , please do share
to sum up, I will take my chance to run the engine with this oil since frequent changes (every other track day) seems to be more logical to me at this point
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UOAs. Mobil 1 US blends seems to be pretty standard affair while their 0w40 Euro-spec blend is much better because it's meeting a higher standard (and the UOAs are solid). From my own nerding-out on VOA/UOAs, the Mobil 1 0w40 is the only OTS Mobil product I'd consider (that's not racing specific) and if you're dead set on 5w-30 then you are better off with the 300v.
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I don't think so Colin, I have also been following the threads on bob's website and my friends had good UOAs from blackstone.. I have a cup that I received from Blackstone sitting in my garage, I am just waiting for the second track day to send the results, I will share the results here..
if you remember Dezoris also had good UOAs result with 0w-20 Redline oil but I still wouldn't consider running 0w-20 looking at those results, FYI, I haven't seen anyone seen that had bad UOAs with Mobil 1 5w-30 and
so the main reason I am sending the 5w-30 Mobil 1 is because I want to see if there's anything abnormal wear &tear on the engine (metal shavings and whatnot) since that could be a good indicator for a failure ...not because I want to see if the Mobil 1 5w-30 is holding up well ..because I am almost sure that it does same (and sometimes even better) protection than those Motul, Redline and Amsoil
you can simply compare their specs sheets to see that ..there's no voodoo magic there, if they both meets the manufacturer's recommended specs(Mobil 1 0w-40 european formula doesn't meet those standards AFAIK) and provide the protection that they dictate on the technical spec sheets , it's fine by me..
to me UOAs only tell if you're about to lose your engine or the oil is the crappiest oil you can find in the market