10-40 or 20-50?

[Spool]

Hey guys.

73' C20 here and recently changed from 10-40 to 20-50. Good move right?

Does the 350 block require 5 quarts or 6?

[Irish_Alley]

why?

[Spool]

A mechanic I know had showed me a wore down cam shaft over the years of using oil with zinc and phosphorous no longer being present in the oil.

The thicker oil is to fill the space.

Thoughts?

[Irish_Alley]

would this mechanic also be the one changing your engine? a few things to think about how does he know the history of that cam shaft? and i have a 94 chevy 4.3 with over 330k on the original motor and a 02 with over 220k. afaik the zinc and stuff is more for the "break in" of a new or rebuilt engine

https://www.hemmings.com/blog/2012/10/18/tech-101-zinc-in-oil-and-its-effects-on-older-engines/

[Spool]

I'm not changing my engine. We know it's the original cam shaft and in the two years of my possession it's always been 10-40.  The odometer most likely was rolled over 999 once or rolled back at one point to read 134k.

The article seems to point to insufficient lubrication upon engine start up in addition to of course break in.

Are you suggesting 20-50 is not a good replacement of 10-40 for a 44yr old engine block?

[Irish_Alley]

what im saying is ive never heard of anyone on here running 20-50 and if they do i would imagine the engine would have more dry starts and would lead to engine failure. then the mechanic youre talking to will be happy to sell you an engine and replace it. if 10-40 isnt good enough for your engine its time to rebuild it anyway

[Irish_Alley]

what ever happened to this post
http://forum.73-87chevytrucks.com/smforum/index.php?topic=34174.msg290924#msg290924

[Spool]

Oil additives. Lucas ZDDP was my choice afterwards.
Mixed reviews on 10-30, 10-40, 15-40 and 20-50 lead to this one.

I'd enjoy hearing different opinions.

[Irish_Alley]

i wouldnt run 20-50, like i said before if you find yourself needing a thicker oil then its time for a rebuild. these engines came with 10-30 and most of use run 10-40 cause theyre old engines. but once 10-40 is no longer doing the trick its time to rebuild. and when i say "doing the trick" i mean holding 7-10 psi at idle or 20+ when cruising

[Spool]

I didn't know the manu was 10-30 originally, but thought it was 10-40.

Would 20-50 really be harmful though, my intention is pro-active, as the engine shows no sign of needing a re-build.

The 20-50 came up a few times over the past year; so I finally made the move.
The suggestion was Jim Grubb Motorsports engine builders (who had showed me a run down cam), a Sabb Mechanic who has a 3rd gen Chevy truck and thirdly, an employer who drives a 59' f100.

If it's going to do damage to my block, I'd remove it but now I'm gonna search deeper before changing again.
She feels smooth, nothing different or slower acceleration.

[Irish_Alley]

"if" you have a new engine you can run 10-30 and be good its only when the oil cant be maintained does anyone ever step it up. if you want better zinc bs then add a additive. i know the only thing i ever add in my 4.3 tbi with 320k is 10-30 with some wear the oil pressure never really goes below 25. the more additives you add like zinc means less lubrication properties of oil. theres a reason why all builders use break in oil then change it as soon as they break in the motor. if all that stuff was best for a motor then they would just leave it in

[Rapid Roy]

So what happened to the 30W we use to use in the 60's and 70's in most all vehicles?

[Irish_Alley]

and the leaded gas

[bd]

You realize you will never hear unanimous agreement from gearheads on which is the "best" engine oil to run.  That's because a little true data is nearly always mixed with fixed opinion - sometimes more than a little.  In southern California and the greater Southwest, 10W-40 oil works really well in seasoned engines.  On a brand new engine or fresh rebuild with tight bearings and clearances, 10W-30 is a great choice.  If you reside in cooler climates, again 10W-30.  On the other hand, if your truck crawls the back roads of Mojave or the Sanoran desert, 15W-50 or 20W-50 becomes pretty attractive for a typical factory engine.  But, what about modified engines?  I run 5W-50 in my 355.  It's happy at 5,500 RPM.  The point is that there is no absolute when it comes to suitable lubrication other than the moving parts of the engine need to be adequately lubricated.  That's what oil does - for the most part pretty well no matter what you are running.  Albeit, the idea of 20W-50 "taking up the space" to prevent cam wear wavers on ludicrous.  Virtually any multi-vis or straight weight oil originally specified for an application will adequately lubricate the moving parts of the engine, including the camshaft and piston skirts - AS LONG AS the high pressure friction modifiers (for example ZDDP) are present in suitable quantity.  This is old news.  Where you might notice subtle differences in the performance of various oils in street machines is over consistently long distance commutes with steady throttle.  Lighter weight oils may provide measurable improvements in fuel mileage if all other variables are maintained constant.  Eat a few extra cheesburgers and an extra twelve pack of beer in one week or forget to air the tires and that could change.  Get the idea?  So, if you want to run 20W-50 in your engine, go right ahead.  It won't hurt anything.  It may cost a little more.  Will it function any better than the 10W-40 you have always used, probably not, unless you change it more often.  But then, you could accomplish the same result with the 10W-40 by changing it more often.... 

Just what you wanted to hear, another opinion.  Use what has always worked.  Why deviate from a proven routine?

[Irish_Alley]

i didnt even take into consideration where you live. here in maryland weather plays a big role in most things we do. i think thats why i use and suggest only 10-40. the further north you go the more you might find people suggesting lighter oil. blaz, vile, rich and vile might have different opinions