5w-20 ok for GMC 6.2l ?

Status
Not open for further replies.
Joined
Apr 2, 2005
Messages
298
Location
SC Coast
I have to change oil in our GMC 6.2L I have a bunch of 5w-20 that I picked up that I would like to use if possible. I have always used 5w-30 in it.


Can I use the 5w-20 without any issue or is it too thin? this is a 2011 with 140K on it

I thought maybe I could mix a couple Qts of 15w-40 rotella that I have here to thicken it up a little, or this a bad idea?
 
I know the 14 and up 5.3 calls for 5W-20, but I wouldn't put it in the 2011 6.2.
 
Last edited:
A pushrod V8 is not the ideal configuration for a water thin oil, especially in warm climates. Of course, it really depends on how the engine is used. Lightly loaded and frequent oil changes will generally provide good results, regardless of oil choice.

Many years ago, I tried a super thin oil in my turbocharged Miata, in an attempt at improving the mileage. What I ended up with was wiped out rod bearings. Of course, it was a 400HP 1.8L engine with 33 pounds of boost.

In the end, oil viscosity is what does the protecting. All the anti wear additives just assist when the viscosity can't do the job.
 
Last edited:
If you want to use your stash mix it with your Rotella it will not hurt anything. One Rotella quart to 5 quarts of 5W20 will get you close to a thin 30 grade which is what ISLAC 30 grades are.
 
Originally Posted by dave1251
If you want to use your stash mix it with your Rotella it will not hurt anything. One Rotella quart to 5 quarts of 5W20 will get you close to a thin 30 grade which is what ISLAC 30 grades are.


I was going to suggest buying some 10w30, but if you have Rotella in stock that should work fine as a Frankenbrew.
 
If not towing or racing, 5w20 is fine in a 6.2L. GM specs 0w20 for its current 6.2L in Silverados (for towing in hot weather even!). I can't see any downside. Yet I'm OCD cautious enough to avoid towing with 5w20. I wouldn't use more than a pint of Rotella if any at all. Additive clash is a big fear here which keeping the quantity of Rotella down could help with.
 
Originally Posted by paoester
If not towing or racing, 5w20 is fine in a 6.2L. GM specs 0w20 for its current 6.2L in Silverados (for towing in hot weather even!). I can't see any downside. Yet I'm OCD cautious enough to avoid towing with 5w20. I wouldn't use more than a pint of Rotella if any at all. Additive clash is a big fear here which keeping the quantity of Rotella down could help with.


Additive "clash" isn't a concern with any modern motor oil.
 
Only the new gen V (2014+ K2xx trucks) is designed for 20 weight oils, and it takes about 8 quarts of it no less. Putting a 5w20 in an older 6.2 is risking a glorious engine.
 
Last edited:
Originally Posted by jdw1222
I have to change oil in our GMC 6.2L I have a bunch of 5w-20 that I picked up that I would like to use if possible. I have always used 5w-30 in it.


Can I use the 5w-20 without any issue or is it too thin? this is a 2011 with 140K on it

I thought maybe I could mix a couple Qts of 15w-40 rotella that I have here to thicken it up a little, or this a bad idea?



0W-20 is specified and has been proven to not have any negative effects on engine wear.
 
Originally Posted by dave1251
One Rotella quart to 5 quarts of 5W20 will get you close to a thin 30 grade which is what ISLAC 30 grades are.


Agreed - I was going to say just add 1-2 quart of 20W-50 with the rest 5W-20....

But adding a little bit of 15W-40 will also do the trick!!
 
little confused on what to do

should mix some oil and not worry or scrap the idea and go buy some 5w-30
 
Originally Posted by jdw1222
little confused on what to do

should mix some oil and not worry or scrap the idea and go buy some 5w-30

Oil is cheap, put what it calls for and rest easy. Use the 5w20 in something else or give it to a friend. We know that the new 6.2 specs a 20 weight oil, what we don't know is what if any changes were made to accommodate a lighter oil. Did they change the bearings or go to a higher flowing/higher pressure oil pump to compensate for a thinner oil?
 
Originally Posted by jdw1222
little confused on what to do ... should mix some oil and not worry or scrap the idea and go buy some 5w-30
Its an 8 year old vehicle, not a new Corvette here. OK to mix in a pint or quart of Rotella to thicken it. Little risk. Doubt anything bad will happen.
 
Just run it straight without mixing. Monitor oil levels and do a UOA if you want to. Not sure how much 5w20 you bought but if it's 100k worth, I'd test it a few times and see how it's trending. If it's 2 oil changes worth, use it then buy the recommended weight.
 
ended up with a special mix!

I found 2 qts of regular 5w-30 I had also.

SO I mixed

2qts 5w-30
.1/2qt 15w-40
3.5 qts 5w-20

hopefully that is close enough.

I plan to use all the remaining 5w-20 in my tundra so all good
 
Originally Posted by paoester
Additive clash not a problem with any modern motor oil? We are talking about frankenstein combinations of oils, not one oil by itself, you understand? ......Degree of polarity, surface competition, antagonistic reactions, etc., all doesn't exist in your fantasy world.
For the truth on this subject, read Molakule's thread (article) on it:
https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/5262512/a-review-of-engine-oil-additives


The truth is there isn't a problem I'm not sure why you are not understanding this. Rotella is using a nice dose of ZDDP, Boron, and Calcium as additives. Nothing to "clash" with a modern PCMO.
 
Originally Posted by crj19


0W-20 is specified and has been proven to not have any negative effects on engine wear.


Utterly and completely incorrect.
 
Status
Not open for further replies.
Back
Top