GMC / Chevrolet 4.8/5.3/6.0

dietz4ibanez

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Yeah I use straight 30w oil in my Kawasaki engines and 10-30w in my Kohler engines..
Not that this really pertains to the thread....

I thought that the 5-30 would be better with high mileage but could be losing lubrication properties sooner... So maybe with the black truck I need to switch to 10-30 or 40..
 

Zembonez

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I ordered up some 100% synthetic 5W30 for the truck. I'll let you guys know what I think.

Thanks Nick!
 

Texas1911

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I thought that the 5-30 would be better with high mileage but could be losing lubrication properties sooner... So maybe with the black truck I need to switch to 10-30 or 40..

Oil doesn't really lose it's lubricity... in a good syn. oil you are only really losing the additives package, which provides some of the agents to improve lubricity (zinc, moly, etc.). The lubricity provided by oil is just because of the barrier it forms between the parts. So long as you maintain that barrier the oil is doing it's job. It maintains the barrier by utilizing the pressure from the oil pump to force oil into the bearing gaps (via the galley holes).

Ultimately the lighter weight oils are better at flowing into small gaps since they have less viscosity, but as a result of this, they will build less head pressure (oil pressure), and may lose some of the load bearing capacity. It's kinda a trade-off, but generally you want the lowest viscosity weight that will work in your vehicle.

In summer, in Texas for example, you may have to increase from a 5w20 to a 5w30 to improve your safety margin. The hotter the oil get's, and the looser the engine tolerances, the more viscosity is generally needed. There are other specifics like shear stress, for example in engines that have very high RPM ranges and operate with relatively large camshafts. The engine imparts a very high shear load onto the valvetrain and as a result they can call for some very viscous oils, which also help the engine cope with the added heat from turning 8000+ RPM.

I personally am not a fan of increasing viscosity in older engines. Unless you know that the motor is running low on pressure then I suggest sticking to the same optimal viscosity. Flow keeps bearings cool, and makes the bearings happy. Most tri-metal bearings can actually melt the primary babbit material off if the oil temps climb high enough.
 

Zembonez

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Main and rod bearing clearance make a lot of difference as far as what oil viscosity works best at what temperature. So does journal diameter and width, oil pump design and capacity, etc... Engine designs vary so there is no blanket theory that covers all things engine on this subject. On severely worn older engines an increase in viscosity can hydraulically adjust for the additional clearance and boost usable pressure. Obviously this is not a long term fix. Most current engines run narrower journals and tighter tolerances (and lighter oils) for the sake of "economy". The result is many engine designs that will hardly do 100K... even with good maintenance.

You might call it the pieceofshitifacation of the auto industry.
 

EMS_0525

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Hope no one takes offense but why would you use a different oil than what the manufacturer recommends ? I got into a discussion with someone about a dirt bike, kawi calls for 10w40... they were putting in 20w-50.... Thats crazy to put oil that thick in when they call for alot thinner oil.... I have ran synthetic in my truck since i bought it with out a problem. I have ran syn in almost all my vehicles, cept for the old blazer that burned alot of oil.
 

Zembonez

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Hope no one takes offense but why would you use a different oil than what the manufacturer recommends ? I got into a discussion with someone about a dirt bike, kawi calls for 10w40... they were putting in 20w-50.... Thats crazy to put oil that thick in when they call for alot thinner oil.... I have ran synthetic in my truck since i bought it with out a problem. I have ran syn in almost all my vehicles, cept for the old blazer that burned alot of oil.

+1

I'd generally stick with what the engine was designed for. I do like to use the best quality oil available but I don't like to tinker with the viscosity.
 

sierra

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Got a friend with a 2004 Ford SDF250 which calls for 5W-20. He will not use it, been using 10W-30 for years and thinks 5W-20 is going to ruin his engine. This guy has been a trucker all his life as well as a mechanic.
 

EMS_0525

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+1

I'd generally stick with what the engine was designed for. I do like to use the best quality oil available but I don't like to tinker with the viscosity.

Me too...

Ford has designed thier motors to run on that oil to get best gas mileage and everything, they are ENGINEERED to use it... why wouldnt you.... Have you see the mobil 1 0w-20 oil? that is for the 5w20 vehilces... its like water.... crazy... but they are designed to use it. The royal purple oils seem thin too...
 

sierra

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I use the TSO 0W-30 in my 2008 GMC and that's all I have used since my 1996 Chevy. Just changed my 2009 CTS4 with SSO 0W-30. Had the Cadi dealer change it for me because I had a free Mobil 1 Oil Change coming. Asked him to use my oil and said he 'no problem".

btw-I went with the OEM Mobil 1 for 6,500 miles and the OLM said it was only at 58% but since the car was built in Oct 2008 a year would be up soon anyway. Car never used any oil in those 6500 miles, so much for engines not breaking in with synthetic oil.

Been using AMSOIL since 1975............
 
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EMS_0525

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btw-I went with the OEM Mobil 1 for 6,500 miles and the OLM said it was only at 58% but since the car was built in Oct 2008 a year would be up soon anyway.

The oil life monitor does not use any readings from the oil at all, the way it determines the life of the oil is engine temperature and engine rotations.... FYI.

I dont use mine or my wifes in her car. I change syn oil every 3k miles.... i know its a little over board, but changing the oil is the cheapest insurance to keeping it running.
 

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