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Old 03-20-2013, 08:05 AM   #21
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Go with da book...30 W.
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Old 03-20-2013, 04:06 PM   #22
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Originally Posted by Daddyo View Post
No, 30 is thicker then 40. The lower the second number the thicker in multi or SAE. The higher the first number the thicker ie:
10W-30 is thicker then 5W-30
10W-30 is thicker then 10W-40
SAE30 is thicker then SAE 40
Don't think that's correct. Read the link psneeld posted. The higher the viscosity rating, the greater the "thickness."
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Old 03-20-2013, 04:09 PM   #23
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Motor Oil Viscosity Grades Explained in Layman's Terms

more detailed oil viscosity explanation
Thanks much for posting that link, psneeld. I learned some things.

Eric-- Did you notice psneeld's link addressed the isue of viscosity aditives encouraging the formation of sludge in multi-vis oils? I suspect this is the same issue you alluded to in one of your earler posts .
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Old 03-20-2013, 06:30 PM   #24
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All,

A good discussion that summarizes all we've elarned in the last 50 odd years.
THe issue of viscosity extenders was an issue and to a certain extent, still is.

What has changed recently (last 10 years) is the understanding that much of your engine wear actually takes place in the first few seconds of engine start when the bearings have the least lubrication. Therefore, having a thinner oil when cold has become far more important than a thicker oil when hot.

The solution to the viscosity extenders problem is to simply change your oil more often.

just my two cents.

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Old 03-20-2013, 07:17 PM   #25
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Marin,
Yes I did and as good as it is it's still a promotional text oriented to convince people they should buy Amzoil.
Talking about rubber aditives that turn to sludge is intended to make the Amzoil look look like a far better product. Amzoil was the only synthetic product lubricant that failed in ultralight aircraft in the early 80s. By failed I mean that numerous pilots had problems w it. I used/use a synthetic lube for 2 strokes that is not compatible w dino oil. It's so "thick" or viscus it says on the bottle not to use it on engines w auto oil injection lube systems. One thing all the engineers agree on is that thicker oil gives greater protection from wear. One must pre-mix it and mix it well as it dosn't mix as readily as dino oil that even has an additive to promote it to mix w gasoline. That's probably because of the guys that just dump the oil in the can w/o mixing.

And Marin yes I was previously "alluding" to the disadvantages of multi-vis oils but my complaint is that the additives are not lubricants and the more additives added the less oil is in the oil. Less oil to lubricate your engine. I don't know how much volume or weight of oil is displaced by additives and I want all the additives that I need to be in the oil. But I don't think we need VI improvers in our boat engine's oil. Just like you don't need multi-vis oil in your car in Florida or California. But in the winter in Minnesota you better have it. Probably 5W-60 if you can get it.


Wxx3 wrote;
"What has changed recently (last 10 years) is the understanding that much of your engine wear actually takes place in the first few seconds of engine start when the bearings have the least lubrication."
I think I've heard that for much longer than 10 years and I think FF alludes to that too. It may be but even in your words "is the understanding" there is a hint of believing that it most likely is more like a probability than a fact. On that one I think I'll need some scientific testing to make it fact in my book. But I buy into that enough to want to crank my engines a bit at least every month or so. Can you think of an application of engines that fail unusually often from "dry" start-ups?

LOOK AT THAT! THERE IS AN AMSOIL ADVERTISEMENT THAT APPEARED JUST TO THE UPPER RIGHT ON THIS PAGE. By that I learned to spell Amsoil correctly.
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Old 03-20-2013, 07:21 PM   #26
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My Perkins ran on Rotella 15W40 (packaged in Ontario)since 1971 and on our first trip south (2001) I loaded up on Rotella. I replenished my stock in Florida (label said packaged in Texas) and at the next oil change started blowing brown smoke.
Yeah brown ! when I looked in the bottom of the container there was a visible brown sludge in the bottom.

After returning to Ontario I contacted Shell head office and was told that each refinery had their own formula, that they had no control over the Texas refinery and they refused to look in to the matter or look at the sludge in the container. This pissed me off so much that I switched to Delo.

I now dipstick every container before I put it in my engine.
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Old 03-20-2013, 07:29 PM   #27
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I now dipstick every container before I put it in my engine.
Good advice. Thanks.
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Old 03-20-2013, 07:35 PM   #28
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Originally Posted by RT Firefly View Post
Greetings,
Mr. D. Your explanation of multi-grade oils is correct to a point but in single grade oils SAE 30 is thinner than SAE 40.
RT did I really say that ........ bad man. I should be punished or forgiven. But you said "Mr D" so it may not be my doing.

Tom B re your original post after all I've said I think you should use SAE 30 but I don't think you'll notice any difference. 15W40 is very recommendable and w the huge numbers of people using it in your application you should feel very comfortable w that choice.

Poker, I think you got some contaminated oil and if you live to be 997 years oil it almost certainly won't happen again.
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Old 03-20-2013, 07:58 PM   #29
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RT did I really say that ........ bad man. I should be punished or forgiven. But you said "Mr D" so it may not be my doing.
No worries, Eric. So far as I know you did not say that 30 wt is thicker than 40 wt in any of your posts. Daddyo said that in one of his posts. Given his experience my guess is it was a typing mistake.
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Old 03-20-2013, 08:30 PM   #30
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I did type that !! Sorry but the hands were working faster then the brain.
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Old 03-21-2013, 04:22 PM   #31
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Tom B wrote;

"I am guessing this is a type-o? SAE30 or 10W30 is thinner than 15W40. Right?"

Depends on at what temperature. The 15W-40 is thicker at high operating temps and thinner when starting up cold.
Google the temperature / viscosity graphs. If its thicker at high temps (200), it's thicker at low temps (50). It seems squirrelly to me to imagine a cross-over.

Am I missing something?

I think I'm going to have to dust off my old fluid dynamics book.
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Old 03-23-2013, 12:08 PM   #32
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It's a more "modern" oil....probably designed for higher performance apps ...so why not?

Perhaps because there is less OIL in the oil?

"Modern" detergent oils contain loads of chemicals 15%+ which are to help the oil do its tasks.

As the oil has to work harder in more modern engines , higher operating temps , higher loads and the burden of dumping exhaust gas back into the intake EGR , for the air police the oil has to do far more .

So the additive package is larger , with less oil doing the lubricating.

This may not be all bad as most of our non EGR engines are so underloaded that help in removing or suspending carbon for the filter to grab may be a good deal.

Same deal with the flour (thickeing agents ) put in multi grade oil.

Thin oil with something to temporarily clump it together is not my (or many users) choice of lubricant.

Yes it scrapes off easier (being thinner) so there is a mileage gain , and for some it will help in cold starts .

Cranking 5 seconds instead of 2 is hardly an advantage that would have me abandon single weight oil.

Should there be a lubrication problem , I prefer more OIL in my oil , as it might be a help.
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Old 03-23-2013, 12:54 PM   #33
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Quote:
Originally Posted by Ben View Post
Google the temperature / viscosity graphs. If its thicker at high temps (200), it's thicker at low temps (50). It seems squirrelly to me to imagine a cross-over.

Am I missing something?

I think I'm going to have to dust off my old fluid dynamics book.
Ben,
Thicker than what is the question. 15W40 oil is SAE15 weight straight oil with additives in it that cause the 15W oil to be as thick as straight 40 weight oil at 178 degrees F. There's no 40w oil in it.

When its cold 15W40 is thinner that SAE30 and when it's hot W15-40 is thicker than SAE 30. This is true only if the viscosity improvers are working
well and not "worn out".

FF says "So the additive package is larger , with less oil doing the lubricating." and "I prefer more OIL in my oil". As do I and this is the main reason I use straight weight oil.
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