10W30 year round?

[Jorge6.5]

Is it safe for a motor to swap viscosities and weights? Say for example 5w30 to 15w40. Can this harm anything in the motor?

 

[SAATR]

Is it safe for a motor to swap viscosities and weights? Say for example 5w30 to 15w40. Can this harm anything in the motor?

Yes, no I'll effects whatsoever. You may get a little more consumption due to different additive packages but that typically only lasts for a couple of oil changes.

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[Ruger_556]

Is it safe for a motor to swap viscosities and weights? Say for example 5w30 to 15w40. Can this harm anything in the motor?

Not exactly ideal but it won't hurt it... Why do you want to switch? It's not going to gain you anything unless the motor is getting tired.

What's up with everyone that just can't accept what the oem recommends? If it didn't matter what oil weight is used why is there even a spec in the book?

 

[Chris6060]

In my '94 I've tried a few different oils. First I tried the regular old Petro-Canada bulk 5W30 they had on top at the local oil change.

Burned that.

Then I tried some Quaker State "High Miler" Semi-Synthetic 5w-30.

Burned that.

Now I'm using Mobil1 Delvac 0w-40 full synthetic with Lucas Pure Synthetic Oil Stabilizer, doesn't burn a drop of this stuff. On my third oil change on it. After 5000kms, my oil came out almost gold after the second oil change.

 

[SAATR]

What's up with everyone that just can't accept what the oem recommends? If it didn't matter what oil weight is used why is there even a spec in the book?

Many reasons. For one, I don't know of anybody with a GMT400 that's still under a factory warranty, so warranty requirements don't matter. Two, economics. I received 10 gallons of fresh, quality motor oil for free. Should I not use it simply because it isn't what my owners manual specs? Three, oil formulations aren't the same as they were when our trucks were new. API requirements for the last several gasoline engine specs ( SM, SN, etc) have dropped the levels of Zinc and Phosphorus in the oils additive packs to much lower levels than were present when these oils were spec'd for our trucks. This can cause problems for flat tappet cam guys, as these are anti wear compounds that help prevent scuffing and galling of can lobes and lifters, especially on cold starts. Heavier diesel oils like 15W40, 5W40, and 0W40 still retain higher levels of these additives, though they are changing too. Four, our trucks are, for the most part, old and worn. They have wider bearing clearances than were present from the factory, and some ( like mine) need a thicker oil to maintain good oil pressure at operating temp.


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[K15 Blazer]

I need to run 20w50...... my engine is really, really worn out...

sometimes I do 10w40 but my oil pressure at idle drops to like... 10

 

[Ruger_556]

Many reasons. For one, I don't know of anybody with a GMT400 that's still under a factory warranty, so warranty requirements don't matter. Two, economics. I received 10 gallons of fresh, quality motor oil for free. Should I not use it simply because it isn't what my owners manual specs? Three, oil formulations aren't the same as they were when our trucks were new. API requirements for the last several gasoline engine specs ( SM, SN, etc) have dropped the levels of Zinc and Phosphorus in the oils additive packs to much lower levels than were present when these oils were spec'd for our trucks. This can cause problems for flat tappet cam guys, as these are anti wear compounds that help prevent scuffing and galling of can lobes and lifters, especially on cold starts. Heavier diesel oils like 15W40, 5W40, and 0W40 still retain higher levels of these additives, though they are changing too. Four, our trucks are, for the most part, old and worn. They have wider bearing clearances than were present from the factory, and some ( like mine) need a thicker oil to maintain good oil pressure at operating temp.


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Zinc and Phosphorous have both been removed from modern day diesel oil also to meet emissions (Has caused some problems with TDI diesels). If you need the heavier oil to maintain pressure or if you have access to free oil go for it. My comment was aimed at those with sound engines that spend extra money on heavy weight oils to not gain anything.

 

[SilveradoGuy85]

Well I did use 10w30 for awhile but then switched to 5w30. The manual for mine says as long as the temp doesn't get below 0° then it's fine to use 10w.

 

[michael hurd]

All oils are too thick at 75F or colder for starting. Since I live where it is pretty darned cold most of the year, I run 0w30 in everything for most of the year. It is quite a bit thinner at start up where most of the wear occurs.

10 PSI per 1000 rpm is pretty much a rule of thumb from most of what I read. A thin oil will flow better, carrying heat away from the bearings and surfaces better than a thick oil. Also, a 5w30, a 10w30 and a straight 30 are all the same viscosity at 100C, so why wouldn't you want to use an oil that flows better where most engine wear occurs?

 

[tanman_2006]

I ran 5w30 quakerstate from 80k-175K and upped to 10w30 quaker from 175-247K when i sold my first 95 K1500 305. I still see the truck running around.

Side story, I saw my old rig broke down on the side of the road in SAD shape on thanksgiving. Stopped to lend a hand. Seems my wiring repair from leaving it parked and mice getting to it ~200K finally let go at 260K. New splice and it was firing again. It had been through 2 high speed drug busts in the past yr and bought at police auction for $200, sad sight but she still sounded ok.