0W40 in Chevy Vortec

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3
Location
Evansville, IN
I have a Chevy Silverado with a 4.8L Vortec engine. I have been using Mobil 1 5W30. I've heard "good to excellent" reviews on Mobil's 0W40 formula. It seems to be well-engineered for longer drains. My owners manual refuses to recommend anything other than a XXw30 oil. I would like to try the 0W40 for it's long-drain capabilities as well as its higher viscosity. Is the reason they don't recommend any 40 weights simply because of fuel economy, or will the heavier oil damage the engine? The truck is no longer in warranty so that is not an issue for me. Any input would be appreciated.
 
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quote:
Originally posted by mdecamps: I have a Chevy Silverado with a 4.8L Vortec engine. I have been using Mobil 1 5W30. I've heard "good to excellent" reviews on Mobil's 0W40 formula. It seems to be well-engineered for longer drains. My owners manual refuses to recommend anything other than a XXw30 oil. I would like to try the 0W40 for it's long-drain capabilities as well as its higher viscosity. Is the reason they don't recommend any 40 weights simply because of fuel economy, or will the heavier oil damage the engine? The truck is no longer in warranty so that is not an issue for me. Any input would be appreciated.
It won't damage your engine. Someone asked a similar question about 15w50 on the Mobil 1 web site. And while Mobil 1 is loathe to go against what a maufactuer recommends, they did say that there is nothing to the prevailing theory that the thicker oil won't properly lubricate the bearings of modern engines. Also, the Shell "Expert" on the Rotella Forum said the only issue to using Rotella (5w40 syn, 15w40 conventionl) in a modern gas engine is the catalyst poisoning that could result from the extra zinc in this heavy duty oil. He confirmed that there is nothing to an Xw40 oil not lubricating bearings properly. [ November 22, 2002, 01:34 PM: Message edited by: XHVI ]
 

Al

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I agree. Just for information: I own a Nissan 2L Sentra. It allows 10W-40 oil as long as the ambient temperature is greater than 0 degrees F. This engine has a higher rev limit and piston speed than the 4.8 L. [ November 22, 2002, 04:08 PM: Message edited by: Al ]
 
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Better look at the hot viscosities. The 5w30 is rated at 9.7 and the 0w40 is 14.4. Could be hazardous to your oil seals if the engine is built for lower pressure. An alternative might be to consider 0w30 which actually has a viscosity of 10.1 or about 4% higher. I have been considering blending to get a little higher in the 30 range by mixing 0w40 with 5 or 10w30. Maybe next summer. RW
 
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I don't understand how that matters. The maximum pressure is limited by the regulator in the oil pump. An engine is certainly not going to fail because it's idle OP is a few PSI higher...
 
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Dick, are you talking about the higher pressure overpowering a PCV system, or internal seals? I agree that the oil pressure would be higher on average than with a lighter oil, even if it just means opening the relief valve more often. Still, I can't see this being a source of leaks. Seals would have to be failing already and would be similarly affected by raising shift points. Or am I missing something? David
 
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quote:
Originally posted by dickwells: Better look at the hot viscosities. The 5w30 is rated at 9.7 and the 0w40 is 14.4. Could be hazardous to your oil seals if the engine is built for lower pressure.
I thought I'd heard it all when it came to reasons not to use Xw40 or Xw50 weight oil. [Roll Eyes]
 
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[QUOTE]Originally posted by mdecamps: I would like to try the 0W40 for it's long-drain capabilities as well as its higher viscosity. [/QUOTE First of all welcome to the site. I would recommend that you have your oil analyzed and find out if you need a different viscosity. Extended drains are great, but without analysis???? I am sure the 0W40 will work great with no problems, but arbitrary drain intervals can be difficult to predict. And just increasing viscosity doesn't assure this. IMO
 

mdecamps

Thread starter
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Evansville, IN
I'm going to start initially with a 7k drain and having it analyzed. If everything still looks pretty good at that point, then I'm going to try and work up to 10K. 0w40 is designed for the european engines that all recommend drains of 10-15k anyway. I don't think it will be a problem.
 
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Dixie
MDE, One thing you have to watch with these big V-8's is the relationship of fuel consumption to relative sump capacity. All things being equal, the more fuel you burn, the quicker the oil will become contaminated. Some of my best results with long drain synthetics have been in four cylinder VW engines that are tightly built and get 30+ mpg. These engines typically have 4.0 quart sumps .... In this case, you have a motor that probably gets 15 mpg? and has a sump of 6.0 quarts as I recall, so it's a somewhat more severe environment - specifically in terms of nitration. I'd test the 0w-40 after 7k-8k miles, but I think you'll be fine here .... For engines that idle a lot, it makes sense to use a fuel consumption criteria as the basis for oil change intervals. Some commercial customers do just that .... TooSlick
 
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901
Location
Northern Illinois
My observations of oil pressure guages tells me that the limit valve is set somewhat higher than most of you seem to think, at least on some engines. I have first hand seen the oil seals blown in a brand new opel manta by using 15w50 Mobil 1. Now that was a long time ago and I have no knowledge of the pressure relief valve situation in an opel, but thats what happened. It was the crankshaft seals that leaked and I have a feeling that the slower drainback from the head also caused the valve seats to be flooded. Just something to take into consideration. TA [ November 23, 2002, 08:38 PM: Message edited by: dickwells ]
 

mdecamps

Thread starter
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Evansville, IN
One thing you have to remember is that oil pressure is the highest when the engine is cold....just watch your oil pressure guage and you will see this. The 0W40 will actually be THINNER than the 5w30 at startup and will only have a slightly higher pressure at operating temperature. According to this theory the 0w40 will never see as high of an oil pressure as the 5w30, therefore not blowing any seals. Does this make sense? Now a 15W50 would be a different story....
 

Patman

Staff member
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Oakville, Ontario
That theory definitely makes sense. Whichever oil is thicker on the cold start will always see the higher oil pressure, regardless of it's operating temperature viscosity. So a 5w50 oil would actually never be as thick as a 15w40. (just that the 5w50 is thicker at operating temp)
 
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