So you really think that a plain Jane 50wt oil gives you more valvetrain stability than a 40wt in every case? Maybe morel should rethink their recommendation on oil weight... Too viscous of an oil DOES NOT mean more protection. Where do you guys get this crap?

A straight 40wt or 50wt is the same viscosity at 100 celcius as any other similar weight oil, PERIOD! The only reason you wouldn't want to run it is because racers use pan heaters because the stuff doesn't flow for squat at startup temperatures. Straight race oils also have in most cases very few friction modification and no detergents(to ward off detonation). These oils are changed frequently, so there is little if any deposit penalty paid.

See here's my beef with your comments. First these lack any data. Second all oils perform slightly different in a given engine design/application. Doubt you tried them all.. You don't have 100's of UOA's backed by documented tear downs, and no offense, but its apparent you understand little beyond the basics of oil, yet your post makes people that might not know any better think you have it all figured out regarding which oil weight to use. Let's stick to the facts.

I don't run straight weight oils. get your facts straight.

Edit in: I get close to the same performance with Rotella 15-40 as I do many other 20-50's.

I run what works best for me.

Your mileage may vary.

========================

BTW: I run synthetics in my snowmobile so I can pull start the damn thing when it's below 0. Bigger the bore, the harder it is to pull. Mines pretty big. No, that's not what she said. LOL.

BTW#2: When under 20F, I run synthetic 5w-30 in my truck and cars so the oil get's thru the motor faster.

BTW#3: My wife's 06 Honda civic won't crank over when below -10F because of 'stiction' (the term we call the cold oil sticking the piston to the cyl wall - same thing that happens with my snowmobile example above) combined with the tiny battery that's in these Honda's. Synthetic 5w-30 let's it crank over no problem.

BTW#4 - Mercruiser's oil is what, 25w-40 ? Not so different in weight than I run...is it ?

Lastly, Borgie, again, I really understand your passion with oil. I do. And we get some info out of it. I just think you get too involved and too heated with it. As I mention in all the oil threads, when was the last time any of us saw any failures do to the type of oil itself ?

Notice, I used no caps, no bolds, no exclamation points - therefore, I am not yelling nor getting pissed. just telling you so you don't assume I am.

Borgie, how many hours have you logged on bbc offshore marine engines? Last i checked you still havent fired up your 600hp 496 you built.

You are very up to date and i strongly feel you are a sharp guy especially when it comes to the articles youve read about oils. I personally have not spent nearly as much time researching oils as you, because simply i dont feel the need to. I have never encountered any engine wear related to improper viscosities or failures from doing so.

once youve logged a few thousand hours using your 10w40 redline, id say your comments arent backed by anything factual or scientific.

Engineers validate their theories by testing them in real world. Lets stick to the facts, like youve said. 100s of uoas or hundreds of hours of successful engine hours...ill take the run time.

See what happens with these oil threads ? LOL.

God they can suck.

Pssst: Still. please. please, one person come forward and tell us you had an engine failure due to a certain oil you used.

Last time I checked this isn't the only engine I've ever built nor boat. I don't just log onto a website and pretend to be an expert. Do you know my sources. Please do a search of all my oil threads and tell me I'm wrong. Simply running a 50wt in anything proves absolutely nothing, so you rationale is utterly false...

And seeing as you have so many thousands of hours of use please share! I seem to remember you recommending higher viscosity drive oil based on other racers and because there was "less fuzz" on the drain plug magnet. Oh and because thicker is BETTER. Please do me a favor and read up on lubricants before you chose to use loose personal experience along with a weak attempt to bash and discredit me..Now that's surely scientific data right there. Only on OSO folks..

Thank you for explaining what engineers do.. They also validate through thousands of UOA's, tear downs with accompanying measurements in a controlled environment. Yes I'm aware. However there is plenty of racing data showing a 50wt oil is in pretty much all cases overkill and much too viscous. Please feel free to read up on the topic. Granted it's one part in a BBC, however, morel does not recommend a 50wt oil for their lifters. Kinda takes the wind right out of SB's statement of more Valvetrain stability.

Did anyone say anything about engine failure???!! Please stop being dramatic to bolster your unscientific and data less "opinion" on a topic you know nothing about.

Wow you pour 20w-50 into a marine motor and it survives season after season. Well hell, that there is the best darn oil weight you can buy. Anything below 50wt must cause instability in Valvetrain(no) and it will actually offer less protection because the number is lower. See your flawed logic?

Uh well I'd like to be able to but.........I only use Mercruiser 25W-40. When you could only get it in dino I ran it. Now that you can get it in semi syn I run that in 25W-40. In the three SBC and the 4 BBC I've owned well you guessed it - no oil related failures. But I've always changed at 25 hrs or seasonally whichever comes first.

Um, yeh,

Wanna Play ?

I spent a few years changing lifters, springs, retainers, rocker arm ratio's (wanna know my findings on those ?) , camshafts, oil pumps. oil pans, windage trays, profiled cranks, and yes,
friggin damn oil.

Wanna know why ?

Chasing hyd lifter instability issues with many, many sbc and bbc engines. The BBC engines ran into it at an earlier rpm than the small blocks.

Drag race. Street Race. MArine. Circle Track.

So bite me ! There's an exclamation point for you.

Scientific or not - show me someone else here including yourself that when thru that much dam schit.

Want me to go further ?

And yes, Now you are pissing me off !

Yes I do wanna play. Please tell me how this in any way relates to a thick oil like 50wt? Please explain your testing. You have zero knowledge of lubricants and it's obvious.... You are pissed, sounds like a personal problem to me. The "well if it ain't broke, don't fix it" approach doesn't work anymore hoss, sorry.. "Frickin damn oil", that's a new term.

Just to remind you, we are speaking on oils here. Not crankshafts, Valvetrain etc. Yes they all become relevant, however again, it's not bolstering your point. Please do some reading and come back once you understand what VI of oil is and the basic base oils.... Until then you are siding with someone who likes 50wt thick stuff. Plain and simply. I'm stating that a 50wt isn't needed in many of these engines. There are always other "variables" however it's always smarter to run a multi grade with a lower cold start viscosity number period.

You are attacking the topic of oil related failure which we aren't even discussing here. A properly designed engine with a modern oil, even with a less than optimal viscosity will likely never fail due to lubricition breakdown. This was something experienced in the early days. Many builders blame oil, however they don't back these claims with evidence.

So please, go further....

I'll go into what I found and why it worked as it pertains to valvetrain stability with HR and HR Rollers .

But first.

Give me a few paragraph history of your testing with oils.

Thank you.