Another Oil discution

[Pu241]

Okay, wow. Where do I start.

1.) No 10w40. Bad idea. It shears to a 10w30. When shearing happens deposits are formed from the broken polymer viscosity index improvers

Really, all 10w-40 shear to 10w-30's?

Then you should also know that a properly formulated oil contains stabilizers (anti-oxidants) and detergents that are designed to minimize "deposits" when vis-breaking of the polymeric viscosity indexers occurs.
Does Amsoil 10w-40 vis-break/shear down to 10w-30?

[gdawgs]

Using 10-40 or 20-50(especially) is not a good idea

Please elaborate as to why this isn't a "good idea"!

The "thicker" oil at startup (the 10W part) provides more oil cushion at startup than the 5W oils.
Thus wear is reduced. Tribological studies have shown that 80+% of engine wear occuring during startup!

Exactly. Which is why you want a thinner oil, so it gets there faster. Both oils leave enough residual lubrication after the engine is shut off and parked.

Modern engines have much tighter clearances and tolerances, especially in bearings, than older engines. So the thicker oil has a harder time flowing through tight pasages.

[Pu241]

Exactly. Which is why you want a thinner oil, so it gets there faster. Both oils leave enough residual lubrication after the engine is shut off and parked.

Modern engines have much tighter clearances and tolerances, especially in bearings, than older engines. So the thicker oil has a harder time flowing through tight pasages.

I agree with most of what you've said!
Most name brand oil will do the job fine, even a 10w vs a 5w oil.
yes, unless you live in the Sahara desert the 20w-50 is probably too viscous as an everyday oil but in applications like racing it holds up well.
I still think the 10w will leave a thicker oil coat (cushion on parts like cylinder walls, bearing, etc) than a 5w oil will. I'm not too sure about how much faster if, at all, that a 5w oil will get to parts faster than a 10w oil.
The usual oil pump relies on viscosity to pump the fluid.
If it has too low a viscosity it will not pump, if too high it will not pump.
But at this point we are likely just splitting hairs!

[gdawgs]

[quote="Pu241
But at this point we are likely just splitting hairs! [/quote]

Agreed.

Probably not much difference between 5w and 10w. I was thinking more of the 20w50. There is a big difference there. And running this in moderate temps isn't a good idea(in an engine that calls for 5w30 or 10w30).

[darkdan]

Okay.

1.) Yes, all 10w40 will sheer even synthetics. Some more than others. So far, the one 10w40 that sheers less (notice, LESS) is AMSOIL's new super expensive 10w40 motorcycle oil. Even with proper PAO basestocks its hard to blend a 10w40 (5w40 is actually easier and uses less or no VII).

2.) Correct, better detergent/dispersant packages will help keep deposits to a minimum, but they will still form regardless of your engine condition or your oil selection. Especially in the ring packs. There's too much heat, pressure, and combustion byproduct for rings to stay clean. That's why I try to beat it into everyone's heads that they NEED www.auto-rx.com

3.) 5w, 10w, 15w, etc have NO BEARING on a coating that is left behind on shutdown. That would depend on the second number. Also, considering even SAE 60 is super super thin at operating temp it still leaves behind practically nothing. It's basically like throwing water onto the bathroom mirror, but with less surface tension, it will run down. Also, synthetics contain esters. Esters are polar by nature and thus are attracted to metal. They will form a molecule layer thin film of protection....which a molecule is better than nothing.

4.) 20w50 would be fine for Minnesota summers and Costa Rica. You'll see a dip in gas mileage. 20w is good in most OHC engines until about 35F to 40F. It's fine for pushrod motors to about freezing. Keep in mind a lot of diesel guys run 15w40 in their engine all year long without a block heater (even in Minnesota the crazy weirdos) and they still last 300k miles, they'd last a bit longer if they'd use 5w40 in the winter though.


Americans have this idea that anything other than 5w30 is too thick for anything in any climate. But outside North America 5w30 is considered too thin.

My recommendation for Costa Rica is still 5w40 or 15w40 for the previously mentioned reasons.

For most of us in the US 5w30 winter and 10w30 summer is the way to go. Otherwise, a synthetic 5w30 or 10w30 all year round depending on what part of the US you live in is the better option. Most people in the south can get away with a 10w30 synthetic all year, but if they use a conventional oil they should still switch to 5w30. Not to mention www.auto-rx.com and FP60 by www.lubecontrol.com

[Fordverde]

After all your info(thanks to all by the way) I made my choice: Esso synthetic 5w50. Now lets make another question: oil filter brand??? fram, bosch, purolator, luberfiner,miltek..... which one???

[darkdan]

Basically, anything OTHER than Fram.

https://www.oilfilterstudy.com

http://home.mindspring.com/~cewhite3nc/index.html

I ran Synthetic 5w50 for a short period of time just to test it out. I lost about 2 to 3 mpg!!!!

[Fordverde]

Guys I ended up putting 10w30 Pennzoil and a Luberfiner filter, Put Prestone all season coolant (the one who does not need to add water). It runs like a dream!!!! I even got the impression that it has a lot more punch in first and second gear. I think he liked the 10w30. I'll used it for the next two changes to see how he behaves. Thanks to all!!!!!!