oil weight

burnan · May 4, 2005

Hey Everyone,

I am new to this forum. I just bought a 2500HD 6.0L. It only has 63 miles on it. I was reading in the manual that GM says to use 10-30 wt engine oil. Does anyone use 10-40 or heavier. I have never believed in lighter oils. I don't see why 10-40 would casue a problem but I would like to read other opinions or experiences. I am surprised they recommend a light oil for a truck that is made to work.

Thanks,

burnan

2500HD4X · May 4, 2005

I use a 5-40 Mobil 1 truck + SUV (Relabeled Delvac 1?) in my 6.0L. It works fine, I cannot tell the difference in mileage and it seems quieter. Before I found the T+SUV I used to run 5qts 5/30 with the sixth quart 15/50 Mobil one. In the summer it gets really hot here and 5-30 just seems thin for towing in 100 plus, I would have a real hard time with Fords 5-20 recommendation...... Anyway, if you are interested in oil stuff you should check out www.bobistheoilguy.com and go to the forums. Type in LS1 in the search feature and you can read all about what people have tried in our engines. Its a good resource if you are interested. Good luck with your new truck and welcome to the forum!

2500HD4X · May 4, 2005

OOPS!!!!!!!! Sorry about that.....It posted twice....

snoman · May 4, 2005

Hey Everyone,

I am new to this forum. I just bought a 2500HD 6.0L. It only has 63 miles on it. I was reading in the manual that GM says to use 10-30 wt engine oil. Does anyone use 10-40 or heavier. I have never believed in lighter oils. I don't see why 10-40 would casue a problem but I would like to read other opinions or experiences. I am surprised they recommend a light oil for a truck that is made to work.

Thanks,

burnan

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The reason they do not suggest 10w40 is that back in the 80s they had some problems with sticking rings that they traced to the VI (Viscosity Improver) that is used in larger amounts in 10w40. It seems it would cook out in the higher temps of those engines back then and gum up the rings over time. Also, there is nothing gaining by using a heavier oil than what is call for because thicker oil also fractionally reduces MPG from increased oil shear forces required in engine when it is used. In hot climates you could use a 15w40 dino oil because it does not have the VI problem or even straight 30 weight. When I lived in Texas for a bit in the 70's striaght 40 and 50 weight was popular durring the summer and even straight 60 could be found if you looked for it. Some car maker are even going to 5w-20 or 0w-20 as the recommanded oil in their vehical to minimize MPG loss to oil shearing and pumping losses. 10w30 dino oil is a bit better in hot weather than 5w30 because it has less VI in it and VI actually takes away fractionally from is ability to lubercate and the 10w30 tend s to be a bit thricker at higher temps (in dino oil) than 5w 30 is.

RICH256 · May 4, 2005

Hey Everyone,

I am new to this forum. I just bought a 2500HD 6.0L. It only has 63 miles on it. I was reading in the manual that GM says to use 10-30 wt engine oil. Does anyone use 10-40 or heavier. I have never believed in lighter oils. I don't see why 10-40 would casue a problem but I would like to read other opinions or experiences. I am surprised they recommend a light oil for a truck that is made to work.

Thanks,

burnan

<{POST_SNAPBACK}>

The reason they do not suggest 10w40 is that back in the 80s they had some problems with sticking rings that they traced to the VI (Viscosity Improver) that is used in larger amounts in 10w40. It seems it would cook out in the higher temps of those engines back then and gum up the rings over time. Also, there is nothing gaining by using a heavier oil than what is call for because thicker oil also fractionally reduces MPG from increased oil shear forces required in engine when it is used. In hot climates you could use a 15w40 dino oil because it does not have the VI problem or even straight 30 weight. When I lived in Texas for a bit in the 70's striaght 40 and 50 weight was popular durring the summer and even straight 60 could be found if you looked for it. Some car maker are even going to 5w-20 or 0w-20 as the recommanded oil in their vehical to minimize MPG loss to oil shearing and pumping losses. 10w30 dino oil is a bit better in hot weather than 5w30 because it has less VI in it and VI actually takes away fractionally from is ability to lubercate and the 10w30 tend s to be a bit thricker at higher temps (in dino oil) than 5w 30 is.

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And this is exactly why synthetics are much better for many users. The 5W30 Mobil 1 does not contain any VI.

snoman · May 4, 2005

5W30 Mobil 1 does not contain any VI.

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Actullay it does but it is done differently than with dino oil and not called a VI but rather reformulation. Syn oil is not bad stuff but the "gotta have" need for it for you vehical to last is greatly over stated. Modern dino oil is darn good stuff.

XFORD · May 4, 2005

I usually run 5-30 Mobil 1 but this time I switched to Mobil 10-30 to see if it would quite down the motor. It did make it quiter but now I smell burning oil. Under the hood of mine says 5-30. Maybe it's there for a reason.

snoman · May 5, 2005

I usually run 5-30 Mobil 1 but this time I switched to Mobil 10-30 to see if it would quite down the motor. It did make it quiter but now I smell burning oil. Under the hood of mine says 5-30. Maybe it's there for a reason.

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It says that for MPG reasons and for reduced cam lobe wear (in theory) during very cold starts not because 10w30 makes it smell. I suspect that you spilled a few drops of oil unnoticed that is burning off. In one "test" truck of mine I have used 10w30 Mobil one for 16 years now in my burb (though I used 5w30 during winter when I lived in Montana) and still do not have to add between changes but I I have also put 200K plus on engine with dino oil too. I plan to keep burb another 6 or 8 years (atleast) and I will continue the test with it. My newest truck just gets dino oil and is changed every 2000 to 2500 miles because it is not driven much. (it is just coming up on 32k and it is over 5 years old)

RICH256 · May 5, 2005

I usually run 5-30 Mobil 1 but this time I switched to Mobil 10-30 to see if it would quite down the motor. It did make it quiter but now I smell burning oil. Under the hood of mine says 5-30. Maybe it's there for a reason.

<{POST_SNAPBACK}>

The 5W30 may give a little better gas mileage while the engine is warming up.

Nothing really gained by going to 10W30.

At operating temperatures there should not be much of any difference between 5W30 and 10W30. Both theoretically have the same viscosity at operating temperature of 100C (212 F), that being the same viscosity as straight weight 30 oil. At 0C (32F) is the temperature when the oils have viscosity equivalent to straight weight 5 or 10. Remember at cold temperatures both of these oils still have viscosity's heavier than at operating temperature.

snoman · May 5, 2005

I usually run 5-30 Mobil 1 but this time I switched to Mobil 10-30 to see if it would quite down the motor. It did make it quiter but now I smell burning oil. Under the hood of mine says 5-30. Maybe it's there for a reason.

<{POST_SNAPBACK}>

The 5W30 may give a little better gas mileage while the engine is warming up.

Nothing really gained by going to 10W30.

At operating temperatures there should not be much of any difference between 5W30 and 10W30. Both theoretically have the same viscosity at operating temperature of 100C (212 F), that being the same viscosity as straight weight 30 oil. At 0C (32F) is the temperature when the oils have viscosity equivalent to straight weight 5 or 10. Remember at cold temperatures both of these oils still have viscosity's heavier than at operating temperature.

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Actually, it has to fall within a specified range to meet 5w or 10w spec at a certain temp and the same for 30 rating but it does not tell you what the oil does when temps are above, below or inbetween spec temps. Also generally the less VI an oil has (5w30 has more than 10w30 does) the more stable the oil will be a higher temps and less likely to break down as rapidly over the service life of it in engine. Example, straight 30 weight will give better and more stable protection than a 10w-30 in a hot engine and will lube it slightly better as well because because it generally lack VI which while improving the viscosity range a bit it actually takes a bit away from the oil lubrication properties (samll though it may be, it does none the less)