oils work by being slinky molecules that entertwine like limp spagetti. The saturated bonds on them keep them from reacting, so they slide along one another. This is the source of "viscous flow" or oils being goopy. This viscous flow is also what keeps the stuff in between the metal surfaces as the oil film is squeezed (like when all those forces come down a connecting rod during the porer stroke). These forces squeeze the film, and the runnier it is, the thinner the layer becomes. If the oils are too thin then this layer can be sqyeezed thinner than either the roughness of the bearings, or even worse iot can be squeezed completely out from between the metal and the bearing surfaces will grind together. this is an oversimplified discription that ignors the "wettability" of the oil (how much it likes to stay in conact with the metal) but it covers the ideas in play.

So, thicker oil = less wear but more drag.
Thinner oil = more power but more drag.

If you're an experimental sort, drain your crank case, fill the crank with gun makers or clock makers oil (real real thin) start your motor, do one dyno run, then get a new motor

Matt

 

I think your misssing it, but close. Thin oil would be great but when it gets to temp it breaks down lose the sliperrness and then the friction comes to play to destroy your engine. Thats why it use to be thicker oils in the heat of summer and thinner in the cold of winter.


Paul

 

where does the heat come from? Either from shear forces in the fluid ( that will increase with decreased thickness) or occational metal-on-metal contact (there is a reason that one of the bearings is made of much softer material than the crank, for example). Thin oil is NOT good for protection, because the surface roughness of the metal surfaces are much greater than molecular diameters. This would allow for much more metal on metal contact, and the bearing surfaces would wear away much faster.

You can get lubricants with much higher breakdown temps than standard motor oils. Our Minis have synthetic oil, and the breakdown temp is much higher than dead dinosaurs. You can get more exotic lubricants with even higher temps, if you want to spend the $. the breakdown temp is only an issue AFTER the metal surfaces are in contact! And thin oils don't do that as well.

The thinner oil in winter is for improved protection during starting, when excessive viscosity can cause too low a pressure at the bearing surfaces, not normal operating temp when the oil flows freely through the warm oil passages, and for really cold climates. Also, many cold areas use oxygenated fuels in winter (here in not so cold No Cal we get winter fuels) that makes less power, so a bit less pumping loss would be nice.

Thin oil = more wear, less pumping losses
Thick oil = less wear, more pumping losses

Of course there are limits (like the oil being too thick to pump through cold oil passeges).

Matt

 

I see what you are saying Dr., but I think you are confusing viscosity of the oil and actual friction between engine parts (requiring contact between the parts, and hence, wear). If an engine lubricant can be made that is of low viscosity (flows easily; less drag) AND reduces friction (i.e., reduces contact between engine parts) then that would be a great potion! I realize what you are saying is that with current lubricants there is a trade off. But we shouldn't confuse friction (between engine parts) and the viscosity of the lubricant. Reducing friction is a good thing to shoot for (while keeping viscosity of the lubricant low to reduce drag). :smile:

 

If i remember from my time watching SPEED tv. there were two product they used and dynoed that showed improvements. 1 Royal purple oil. (complete oil change) and 2 Motor up horsepower in a bottle.

 

Also, if the viscosity is low, less force is needed to displace it. So no matter what (Ignoring boundary effects) a less viscous fluid will have a thinner film and there will be more surface wear.

Another way to put it is the high viscosity IS what reduces the friction between engine parts.

So I pretty sure I'm not confused , I'm pointing out that the two are coupled. This coupling is why no one has found a cost-effective "magic liquid" that really does a heck of a lot in double blind tests.

So back to this stuff here. They do a demo on a show that shows a pretty impressive gain, but the independant tests (on admittedly different vehicles), done in a with a control vehicle for normalization, showed improvement, but not as much as what what shows here. If they do it by viscosity change to reduce pumping losses, they pay with increased wear. The question of how much is open, but the trade of is unavolidable.

There is lots of interesting physics and chemistry at the boundary layer, and it is possible to make real changes here, but this is not what was referenced in the TV explanation.

FWIW.....

Matt

 

So, the statement "reducing friction increases wear" should really be "reducing VISCOSITY increases wear", right?

(The hosts stated that the magic fluid reduced engine friction, hence we would assume the fluid INCREASED the viscosity.)

 

The other thing that comes into play with oil and engine wear is "sheer strength"; that is the oil's ability to resist being squeezed from between two metal parts. This is where synthetic oil has a big advantage over conventional oil. Mobil claims that their full synthetic oil has "700 times" the sheer strength of conventional oil. Thus it will provide superior protection at lower viscosities. This helps the oil to circulate better when cold and reduce wear during engine start-up.

 

Exactly. You don't need to worry about using thicker oils in the summer or winter or any viscosity anything as long as you are using a high quality synthetic. When the sheer strength is high enough you don't need to worry about viscosity. Some people, espesialy older people in my experience, still tend to think that thicker oil equals more protection. Back in the old days when oil was not very sophisiticated this was probably true but now with all the advnancment in oil technology it simply is not. 5 or 10w30 is fine for 90% of situations and vehicles. Just use synthetic in all your cars, as long as you don't have too high of miles before switching, and don't worry about it.

 

OK, I'll admit it...I watch Orange County Choppers, must be the big guy with the walrus moustache that attracts me...they do have a great shop, however.

did you see the show where they took a brand new built motor and with typical (for that show) knucklehead reasoning fired it up with 60w that had been sitting at 30 degrees, then they dynoed it (reminds me of the sparkplug thread). fried pistons, cracked a cylinder.

I run Mobil 1

 

Re: the Sports Car Revolution bit, it seems the easiest explanation would be that the "stock" vehicle had heavy weight oil in it. Swapping from heavy oil to light oil (synthetic or otherwise, or dilluting the heavy oil) should definitely gain some HP on the dyno.

 

They didn't change the oil, they added their additive. The bottles only hold 10oz.

It could have been old oil, tired engine etc. I imagine the worst you car is the better the result. SO I would doubt you would see some huge change in a optimally set up engine.

Paul

 

Good grief, I checked out this site, it's way over the TOP.
Some of the comments sound familiar though and it seems this discussion would be right at home there.