Doesn't work on Illegal immigrants.

And your post cleaned the beer out of my mouth ! lol Hilarious !

Correct !

This is the umprecendeted case where used oil gives you everything....including total protection !

LOL. I edited it a little better since then. Doh.

Went back and reread , you got me again . ROFLMAO !!!

You are so anti 50w oil and love thin oil! lol You always post up that guys running 15w50, 20w50, 25w50, are simply doing it all wrong. I have never ran anything 40w in any of my marine engines, and about a million other guys have run 15w50, 20w50, 25w50, in high power marine engines for decades with great results. My buddy had a pair of 454 Mags in his old boat. They had 20w50 (never a specific brand, whatever was on sale) in them, since the very beginning. He sold them with over 900 hard hours, and the valve covers had never even been off! Oh, and his oil temps never exceeded around 180*.

I'm definitely no oil expert, but from my own experiances with marine engines, while it may work, I personally would not run 10w40 in my engines. For only one reason. I have never seen anyone run 10w40 in a loosely clearanced 800HP marine engine that sees long periods of extended high rpm running, and I sure don't wanna be a ginny pig. I'm gonna go with what I know has worked for me, and many others for a long time. My boat does not need to meet federal EPA laws, fuel mileage is not of a concern, I don't operate the boat when its below 70 degrees F, and I could care less if a thinner oil nets me 4hp at 5500rpm. I have never seen any oiling related issues when tearing my engines down, so I cant complain nor see a reason to change. It be like saying I been using the wrong crankshaft material for all these years, but yet never broke one, nor have had anything but great results using it for all these years.

All these oil threads about which brand is best, which viscosity is best, I'll bet that 95% of the posts are based on opinion, with 5% actually having factual data on what worked best.

But since we are talking opinions, I say stick with quality oil and filter, keep the oil temp under control, change it often, and go have a good time. Start doing things like using some walgreens shelf oil, too small of an oil cooler that cant control oil temps, too 0w20, straight 70 weight in a 496 mag, and stuff like that, and you may find yourself wanting to change recipes after it cost you an engine or two.

If we know say a 10w anything, flows like a straight 10 oil at winter temperatures, or a 15w flows like a straight 15 at winter temperatures, what does it do at 80* temperature? How about 140*?

Another thing alot of guys don't consider. We are almost all running pushrod V8's. Pushrod engines are a bit more forgiving with heavier oils, than say an overhead cam engine. I would personally NEVER try running straight weight oils, or any heavy weight oil in an overhead cam engine.

I love the idea of my engines getting adequate oil flow when I twist the keys on a summer day at the launch ramp. What scares me, is when I am leaving the harbor, my oil temp is at 90 degrees still, and I have to throttle the engines up to 3500RPM and get on plane, and stay there until the oil comes up to temperature. I'd be worried about not having enough protection at those temperatures, if the oil is too thin.

So my question is, what is the difference in viscosities between a 10w, 15w, and 20w at those temperatues? Many times on cold lake michigan, it's miles of running at 3500RPM, before my oil heats up. Sometimes, I cant resist and start running it hard before the oils fully warmed up. I am not so much worried if my rockers or cam are getting oiled at that point, Im more worried about metal to metal protection and film strengths.

I guess what I am asking, is what advantages as far as oil flow is concerned, can be seen at say 75* degree sump temps when starting the engine, when dropping from a 20w to a 10w, and what disadvantges, from a viscosity standpoint, can be seen at say 140* deg oil temps?

I do not see 20w causing cold flow issues, at 75* sump temps. At -10* F, sure, I can see that. Borgie, maybe you can better answer as I do know you've done lots of oil homework

I'm with you MT.

IMHO - some read way to far into things.

I can tell you this. I've been beating the crap out of hydraulic and hydraulic roller sbc and BBC for a long time. I can honestly tell you I get faster mph (track speed and boat speed) with heavier oils. 15w-40 to 20W-50. I don't run thicker (don't have the ballz) as some boat racers like Straight 40 or straight 50.

Valvetrain stability means 1 million % nore to me than cold flow.

I'm careful with my oil temps before I smash my throttle thru the dashboard - or gas pedal thru the firewall . Doesn't everyone ?

More cushion for the pushin - if you know what I mean ? LOL.

A 10w-40 flows as a 40wt at 100 degrees celcius. A 5w-40 is the same. The benefit is that it has less resistance to flow at startup. The lower number isn't effecting the hot flow viscosity.... Conventional oils accomplish this by using massive amounts of viscosity index improvers (VII's), whereas a synthetic, we will use a water synthetic for example, uses zero viscosity index improvers as its viscosity index is naturally high. These Ester based oils flow extremely well at startup in even frigid temperatures and have shear strength that cannot be attained by a conventional nor hydro processed or group III oil.

Below is a very good read for those interested. I get my information from many sources, but this is very easy to digest and a great starting point.

http://www.bobistheoilguy.com/motor-oil-101/

Increasing viscosity does not automatically equal more protection. Let's not use the example of CAFE compliant or emissions please, as that's plain ridiculous... A 10w-40 oil like redline is a racing oil. It's a true 40wt oil and is by far one of the most thermal and shear stable products out there. In short its not some fuel conserving 20wt oil. There are other oils in its league, but not many.

Morel actually wants a 40wt if I recall in speaking to Madera. A 50wt oil is thick as molasses. Ok fine it "works", but is it optimal?! I think not. Run what makes you happy. 50wt oils are antiquated. Back when engine builders (none who are qualified to speak on motor oils) thought thicker was better.. Guess why? Because oil was terrible back in the 60's, 70's and 80's. The reason you had to run a thick oil was due to the fact that it would shear down to a 30wt in a very short time... So 50wt was the s**T! Problem was that these guys didn't know why it worked and just surmised well the thicker, the better.. No science, no data. If it isn't broke, don't fix it mentality.