Does thinner oil heat up more quickly on start up?

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FZ1

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Thanks. It would seem that the thinner oil would allow the engine to heat more quickly on start up than a thicker oil. Why do you think not?
 
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 Originally Posted By: Bryanccfshr
No, it will be closer to operating viscosity quicker/
the OP's question is flawed because the thin and thick oils start off at different viscosities. so technically "thinner oils reach op temp quicker" is correct. you would have to compare the slope of the viscosity vs temp curves to see which one has the steepest downgrade i.e. heats up the qucikest, but, even if the thicker one had a steeper slope (i.e. heats up quicker) it will likely still be more viscous than the thin oil when comparing it up the temperature scale...
 
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Thicker oils are harder to shear. They generate more friction and heat in doing so. They require more power to pump them. Keep in mind (as Bryan is trying to state) you're always on a sliding scale of view when talking about viscosity and temp. Except for the differences in starting and ending viscs, both will transition through the same viscosity at different times and temps. Heavier oil, in my observations, has a steeper initial curve in warming, but no difference in overall length (time to normalized temp -whatever that may be).
 
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I havent noticed any differance in warm up time between ASL 5w30 compared to Rotella 5w40, but I did notice that the RTS 5w40 took longer to cool back down to normal cruising temps after a few hard pulls. Motor spec'd for 5w30
 
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Just a guess, but I think thinner oil will heat up and cool faster than thicker oil. I think once heated up, thicker oil will take longer to cool off, JMO. I'm pretty sure someone has tested this and a factual explaination can be given. AD
 

FZ1

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Thanks ,guys. In our dearly departed thread from last night, the engineering paper stated that the most important factor in engine start up wear was coolant warm up. So it would seem that 1. you want a thinner oil that warms more quickly on start up.2. The farther North you live,the more important is is to garage your car and/or consider a block heater to help the car warm faster on start up. Thoughts?
 
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 Originally Posted By: FZ1
Thanks ,guys. In our dearly departed thread from last night, the engineering paper stated that the most important factor in engine start up wear was coolant warm up. So it would seem that 1. you want a thinner oil that warms more quickly on start up.2. The farther North you live,the more important is is to garage your car and/or consider a block heater to help the car warm faster on start up. Thoughts?
True. The more north you live during the colder months the better a garage, thinner oil, a block heater, etc. would be. The ultimate setup would be a block heater with an oil pan heater. Given a choice of only 1 I think an oil pan heater would be better choice since it is usually attached to the bottom of the oil pan, and heat rises, at least that is what the Wolverine Oil Pan Heater people told me. They said if you want to warm an engine heat the oil, if you want to warm people heat the coolant. Obviously opinions vary.
 
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I have to agree 100% on the oil pan heater there is always talk about cold start wear . The time it takes the oil to get to the oil pump from the pan is the most important item on the list of what causes cold start wear because it is probably the only thing that will make a difference in extreme cold.
 
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 Originally Posted By: Steve S
I have to agree 100% on the oil pan heater there is always talk about cold start wear . The time it takes the oil to get to the oil pump from the pan is the most important item on the list of what causes cold start wear because it is probably the only thing that will make a difference in extreme cold.
That's how I feel. The only question I have is once the engine is fired up, does the oil cool off as it hits the colder upper regions of the engine? Or is enough heat generated to maintain the temps achieved by the pan warmer, and the temp slowly rises from there? That's why I think a block heater/pan warmer is the best combo for Northern USA and Canada. But given a choice of only 1 I'd still go with the oil pan heater. JMO
 
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 Originally Posted By: oilyriser
Thin oil will flow through the bearings and heads sooner instead of getting bypassed back to the sump, so it should warm up faster.
No, as long as it's correct for the ambient temps thicker oil will flow through the bearings and heads just as quickly.
 
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 Originally Posted By: FZ1
Thanks,man.
I told you, it's exactly as I said in the other thread.
 
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 Originally Posted By: BuickGN
 Originally Posted By: oilyriser
Thin oil will flow through the bearings and heads sooner instead of getting bypassed back to the sump, so it should warm up faster.
No, as long as it's correct for the ambient temps thicker oil will flow through the bearings and heads just as quickly.
I missed the other thread and the engineering paper. Can somebody post a link to it again? I see little way for the average car owner to tell how much the oil pump is bypassing.
 
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 Originally Posted By: BuickGN
No, as long as it's correct for the ambient temps thicker oil will flow through the bearings and heads just as quickly.
Exactly
 
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 Originally Posted By: labman
 Originally Posted By: BuickGN
 Originally Posted By: oilyriser
Thin oil will flow through the bearings and heads sooner instead of getting bypassed back to the sump, so it should warm up faster.
No, as long as it's correct for the ambient temps thicker oil will flow through the bearings and heads just as quickly.
I missed the other thread and the engineering paper. Can somebody post a link to it again? I see little way for the average car owner to tell how much the oil pump is bypassing.
BGN's observations are from watching oil come through the pushrods onto the rockers virtually instantly after engine start-up. I have made the same observations on a smallblock Ford. These are the last components in the oiling system.
 
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I use TWO block heaters PLUS an oil pan heater. that way my engine is happy, and i'm happy because the cab warms up quicker and the defrost works right away. What is the effects of temperature on shear? I would think that if the oil is highly viscous, then molecules would not slide past each other as easily, and they would shear more. That makes me think that pre warming my oil helps to prevent it from shearing. No?
 
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Viscosity when cold is my only consideration, and that is important. Thinner oils do run cooler, like when on a long run on the highway - maybe 10 deg. F or so. But are thin oils warmer/cooler from start to mid temps.? Not an issue, and has no practical value.
 
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