Oil Viscosity Explained

Gee, how can that guy get such access to Mobil 1's teams?


Interesting that they/he stressed that your viscosity is to be matched to your operating temperature. Hotter temps are matched with more viscosity, so your net viscosity/behavior will be optimal at your expected elevated temperature.

What this, of course, makes me wonder, is, "why not just put a truly massive oil cooler on the car, still thermostatically controlled, so no amount of beating on the car at a track or the desert or wherever you go will result in the same oil exceeding its optimal actual, at-that-moment viscosity/behavior?"

I feel the same way about all the engine's coolers, including a cooler like Gale Banks' rear axle airflow-scooping cooler cover, which obviously is NOT thermostatic. I do understand that one CAN overcool one's fluids, which is why big rigs have shutters on their radiators which are also thermostatically controlled.

I really don't like anything being undercooled. Coking oil and bubbling coolant are not things I want to ever have happen.

On a side note, Detroit Diesel, with their integral-to-the-head main fuel rail, have experienced, on the series 60 four-stroke, coking of their actual FUEL due to the heat from the firedeck, as David F. Merrion described it, I believe.

Detroit Diesels can thus benefit from the fuel being cooled prior to entering the head/fuel rail passage.

MTU diesels, in the huge size, such as near 1MW or so, also employ fuel cooling. It's a part of why an actual proper installation of one on a boat is so complex.

But, viscosity versus temperature: I know cars survive while driving in stupidly hot weather, such as Death Valley, but could we do them a favor by cooling them better, or, being willing to give up a few points of efficiency to protect them with more viscous oil?

I mean, if the price of protecting your car is a few extra bucks a week, but surprise catastrophic/whatever damage is avoided, why not? I know a bigger oil cooler will help, but what a bigger cooler cannot do is take the oil, while it is still inside the worst head-producing parts of the engine, and cool it before it gets to the next part of the engine on its intra-engine travels that occur after the oil arrives from the cooler. If you can cool the oil to sub-zero temps to try to fight off extra thermal stress, it will still not be able to shed the heat from the engine as the oil goes from A to B (such as being flung up by the crank) while it is already hot.

I can tell you from direct experience, dumping straight 60 weight in a (relatively low-performance V8) car REALLY makes the engine feel like it is wading neck-deep through molasses. The engine feels like it is being held back at all speeds, but especially when you try to "blip" the throttle. It feels more like a suggestion than a command.

On another note, one Lamborghini, the Miura, had a common crankcase/transmission case, so they split the difference of 50 for the engine and 90 weight for the transmission by filling the whole thing with 70 weight. Yes, straight 70 weight. In an engine and transmission. I do not think that lack of viscosity was ever a problem for that engine. I am not sure that old-school straight 70 was good for the transmission, however.

 

You lost me at 'Gee'

 

That clears up a minor bit of confusion for me. I have the 6.1 liter Hemi. The cap on the oil filler says fill with 0W-40. The owner’s manual and user guide say to use 5W-40. Various helpful souls on this forum have suggested one or the other, but which is best? According to that video, it sounds like it really doesn’t matter, since I live in south Florida, where the temperature never goes below 40 degrees F. Remember, the factory recommendation has to apply wherever these cars are sold, so maybe using 0W versus 5W makes a difference in Anchorage Alaska, but I doubt an engine that spends its life here would care. I could probably go with 10W-40 as well. Thoughts?

 

Here's a page out of the Owner's Manual:



This one's from the User's Guide:



Apparently, Dodge changed their recommendation in the 2010 model year. The problem I have is that 5W-40 is hard to find. Well, at Walmart anyway, where I go to get oil cuz they have pretty much the best price around. And when I do find it there, it's the "European Diesel Blend" or something like that, so I'm not sure that's the stuff I should be using. But the 0W-40 is always available, and for a good price, so I've been going with that. I reckon the 10W-40 wouldn't hurt, being in South Florida where it's always hot, and that's easy to find too. As long as I stick with the "40" number on the high side it should be ok.

At the end of the day, changing your oil and filter regularly is probably way more important than the difference between 0W or 5W or even 10W, but it's nice to know you're using the best oil for the car.

 

I think a little bit before here is where I started ignoring Cloverdale for months due to snide and worthless personal criticisms, like these.
This is the first time I've seen this comment from him.
So, I guess he lost me first.