10W-40 for Chevy 350

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sidschev

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isnt the 20-50 diesel oil a detergent oil ive been told its not good fer gas engines because it cleans too good , but then when ive looked at diesel oil change that stuff is pretty nasty looking black goo....
 

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isnt the 20-50 diesel oil a detergent oil ive been told its not good fer gas engines because it cleans too good , but then when ive looked at diesel oil change that stuff is pretty nasty looking black goo....
Basically all engine oils are detergent oils.
Afaik only SAE 30W is non detergent.
You’d use non detergent oil in things like compressors or some hydraulic applications.
 

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isnt the 20-50 diesel oil a detergent oil ive been told its not good fer gas engines because it cleans too good , but then when ive looked at diesel oil change that stuff is pretty nasty looking black goo....
No 20w50 castrol is a common gas engine oil real popular with air cooled. The rotella t4 15/40 is labeled as a diesel oil, but recommended by their tech line on gas flat tappet cars because of the still high dzzp content.
 
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Castrol 20-50 is dirt cheap. Has been for a while. Not good or necessary for a tight new engine IMO or anything less than warm weather but it’ll run fine in a small block or a LS.
I only posted because the OP was questioning concerns of cold start differences between 10/30 and 10/40. There is none. Didn't see where anyone else answered that.
I have never looked at the Castrol. I was referencing the mercury oil making a point that these engines don't mind heavier grades of oils. I did make a mistake on their recommended grade though. It is actually a 25/40. They are asking close to $30/ltr now in these necks for it. I do run it in my 25 merc jet but it only takes 1.5 ltrs and is under warranty. Will never catch me putting it in my 350 at that price, but lots of people do.
 

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Basically all engine oils are detergent oils.
Afaik only SAE 30W is non detergent.
You’d use non detergent oil in things like compressors or some hydraulic applications.
Yeah you have to look for non-detergent oil.

I was sold on the 15-40 after I bought my work vehicle, 2004 Blazer with a 4.3 V6. It had 110k on it as a government vehicle. I put 4000 miles on it with regular driving, went to do a normal oil change and the oil looked basically like it had just been poured in. I know it’s from good maintenance before me but 15-40 is what they were using and I’ve never had an engine oil look so good after 4k so I continued it. The particular brand they used is only available in drums so I went with Shell
 

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Chevy valve stem seals don't cost much more than a jug of heavy oil. A cheap valve spring compressor and some rope and you can change the seals out in an afternoon without a compressor.
 

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I only posted because the OP was questioning concerns of cold start differences between 10/30 and 10/40. There is none. Didn't see where anyone else answered that.
I have never looked at the Castrol. I was referencing the mercury oil making a point that these engines don't mind heavier grades of oils. I did make a mistake on their recommended grade though. It is actually a 25/40. They are asking close to $30/ltr now in these necks for it. I do run it in my 25 merc jet but it only takes 1.5 ltrs and is under warranty. Will never catch me putting it in my 350 at that price, but lots of people do.
I only posted because the OP was questioning concerns of cold start differences between 10/30 and 10/40. There is none. Didn't see where anyone else answered that.
I have never looked at the Castrol. I was referencing the mercury oil making a point that these engines don't mind heavier grades of oils. I did make a mistake on their recommended grade though. It is actually a 25/40. They are asking close to $30/ltr now in these necks for it. I do run it in my 25 merc jet but it only takes 1.5 ltrs and is under warranty. Will never catch me putting it in my 350 at that price, but lots of people do.
My bad, I didn’t realize you were speaking about a small 4s outboard. I presumed since we basically only talk about Chevy trucks here that you were referring to marinized small blocks and big blocks, not a type of engine that is completely different.
And your prices are not the norm. Or even close. Never heard of 25W40 but looked it up and it’s $30-40 USD a gallon here. Unless you buy Scamzoil.
And I’ve never heard of anyone running it in a vehicle. But I don’t live in Northern BC.
 

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All good @Grit dog. You think our specialty oils are ridiculous in small town northern bc? You should see what they ask for a bottle of water in the stores while all our rivers are all fed from short runs from glaciers.
Mercury recommends 25/40 in all their engines (including the 350 sterndrives). It is FC-W (marine) and a bad example for all purposes of this thread. The viscosity numbers were what I was getting at.
Regardless, I just use 15/40 in my (sb 350) inboard. Just whatever leftovers are laying around the shop from different jobs. My daily driver is a duramax and gets the same. I splurge with the 6.7 in the service truck but it runs around at 8600Kg. It gets 5/40 @ 16/ltr.
 

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Yeah you have to look for non-detergent oil.

I was sold on the 15-40 after I bought my work vehicle, 2004 Blazer with a 4.3 V6. It had 110k on it as a government vehicle. I put 4000 miles on it with regular driving, went to do a normal oil change and the oil looked basically like it had just been poured in. I know it’s from good maintenance before me but 15-40 is what they were using and I’ve never had an engine oil look so good after 4k so I continued it. The particular brand they used is only available in drums so I went with Shell
I've run 15w40 in most of my rigs for years off and on diesel and small blocks alike. As long as it's not the cheap red cap delo. Forget that $#!t.
 

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diesel is very high detergant and it has no zddp in it no more its not made for gas eng period
 

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why do u run diesel oil ?
Because it generally has very good shear stability and used to be decidedly cheaper to buy in volume. Also the simplicity of it. With a dozen or more small engines and automobile engines, in my climate it’s mostly a one size fits all solution.
Also in high load gas v8 applications, like boat engines, it has traditionally been recommended by the company that marinizes the engines.
 

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diesel is very high detergant and it has no zddp in it no more its not made for gas eng period
Ok, sounds like you feel strongly about it. Good news is they sell 100 flavors of oil. Pick the one you like. I thought you were asking a question, not a leading question.
 

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I had a self-inflicted problem where I pinched a couple valve stem o-rings many years ago, which let oil run off the retainers down the valve stems. These seals solved the "white smoke on startup" problem 100%. I think mine were Fel-Pro. They were in stock at my O'Reilly Auto store.

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Because Chevy says to use 10w30 lol. It actually smokes a lot less on startup now. There's still some but a lot less.
The main reason GM and Chevrolet and all the other manufacturers have gone to recommending lighter weight oils, (such as 10W-30) is to reduce their corporate fuel economy MPG ratings. Average to cost millions of vehicles maybe they gain a point here and. I doubt whether an individual would ever see a difference in gas mileage going from 10W-30 to 10W40.
Should not be a problem, as others have said, unless you're operating and very cold temperatures. This is only because it's more difficult to spin a cold engine with thick oil than it is with thin oil.
 

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