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Old 02-20-2007, 05:40 PM   #11
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Quote:
Originally Posted by bonnie94ssei
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Hotter temperatures decrease the life of engine oil...but also decrease engine wear when oil life isn't taken into account (think about cold starts).
Are you saying that hotter temps due to a 195 stat will thin the oil quicker over time and allow for more protection on cold starts?

I wouldn't say that'* reason to keep a 195. If you wanted more protection at cold starts, use 5W as opposed to 10W (especially in winter), and/or switch to synthetic oil, and keep the 180 in for more protection while you are driving, when you need the stat most.
Nah, I'm just saying that...at least the impressions I'm getting from searching around, the engine wears more the colder it gets...perhaps to a point.

So if you take oil life out of the picture... (the hotter it is, the shorter the life of the oil) if you ignore that fact, then hotter engine temperatures result in less wear.

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My engineering friends have told me, (and I believe them) that higher operating engine temperatures should produce better efficiencies.
As an engineering student, I can confirm this. The basic theory goes like this:

1.) The hotter the combustion chamber temperature, the less heat loss there is through the block/heads.

2.) The less heat (energy) lost through the block/heads, the more there is to power the car.


Granted, fluids last longer with lower temps...but if you have the necessary cooling capacity to keep your oil/tranny fluid cool, then higher combustion chamber temperatures can yield better efficiencies.


One thing I'm beginning to wonder...are the lower temp thermostats suggested for longevity or for performance?
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Old 02-20-2007, 07:07 PM   #12
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Longevity, Performance, and fuel efficiency. All three.
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Old 02-20-2007, 07:14 PM   #13
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Quote:
Originally Posted by 95LHS
So if you take oil life out of the picture... (the hotter it is, the shorter the life of the oil) if you ignore that fact, then hotter engine temperatures result in less wear....snip...
One thing I'm beginning to wonder...are the lower temp thermostats suggested for longevity or for performance?
Again, wrong answer.

Engines are made of various metals. All of them expand with temperature. Take piston rings for example. The hotter they are, the greater the pressure they exert against the cylinder walls. This also sets the minimum engine temp. Below 160 F the fit of the rings is loose enough to produce blowby, so this is considered the normal lower limit to the engine temp range. So, as the temps rise, the force pressing the piston rings into the cylinder walls increases. A running temp of 195 produces more force than 180, and hence more wear on the cylinder walls. ( Physics again..coefficient of sliding friction with the pressure of the rings to the wall being the normal force ) Also, the pistons are of different composition than the block, so they expand at a different rate with temp changes. Run too hot, and you have a real problem with the components stuck against each other. Same-same for bearings, wrist pins, etc. Run the engine above the temp range and you run out of clearance between the moving parts.

Also, the engine cannot run at the efficiencies you alluded to. In theory it sounds good. In fact, the heat output of running at stoich 100% of the time will ablate every metal surface of the motor. You could build engines out of every exotic metal you can lay your hands on, but then again, who could afford it? So while hotter and leaner sounds good on paper, in reality, cooler and richer will yield a higher power output (Denser fuel air charge, more aggressive spark timing with a lower risk of pre-detonation, less need to mix exhaust gas back in.)
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Old 02-20-2007, 07:18 PM   #14
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Quote:
Originally Posted by 95LHS
Quote:
My engineering friends have told me, (and I believe them) that higher operating engine temperatures should produce better efficiencies.
Quote:
Originally Posted by bill buttermore
My engineering friends have told me, (and I believe them) that higher operating engine temperatures should produce better efficiencies. But theory and practice are two different things, and engine oil and transmission fluid at 180 work better and last longer than they do at 200.
We call this: taken out of context. Doesn't sound the same when you have the entire quote, does it?
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Old 02-20-2007, 07:34 PM   #15
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Quote:
Originally Posted by bill buttermore
Quote:
Originally Posted by 95LHS
Quote:
My engineering friends have told me, (and I believe them) that higher operating engine temperatures should produce better efficiencies.
Quote:
Originally Posted by bill buttermore
My engineering friends have told me, (and I believe them) that higher operating engine temperatures should produce better efficiencies. But theory and practice are two different things, and engine oil and transmission fluid at 180 work better and last longer than they do at 200.
We call this: taken out of context. Doesn't sound the same when you have the entire quote, does it?
Well, although I didn't quote your entire post, I replied to it in its entirety. If you read my whole post (a novel idea!) you'll see that I wasn't trying to take anything out of context...just treating your points separately.

Sorry if anything was misconstrued.
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Old 02-21-2007, 01:49 AM   #16
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The part of my quote that you omitted (and did not address) that concerned me was not the effect of heat on lubricants, but my point that there are huge differences between a theoretical heat engine and theory put to practice in the 3800 Buick. These have been ably voiced by Curt above, who makes the argument far better than I could. I thought it misleading to parse my comment, as it made it appear that I agreed with your assertions, when that was only in small part, true.

This discussion reminds me of an old joke. A gangster, wanting to clean up at the races, kidnaps a theoretical physicist and forces the man to come up with a technique to determine which horse will win a given race. After much effort, the physicist excitedly exclaims: " I have the technique you demanded." When asked to explain, the physicist began: "First, assume a spherical horse..."
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Old 02-21-2007, 09:39 AM   #17
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again,

any time anyone comes in here claiming bad things about reduced temp thermostats, all they can come up with is theory. Why cant people just take the advice and knowledge of the thousands of members here and make some use out of it, instead of producing scientific THEORY that doesnt include all of the facts or variables.

There is also no way to determine if the thermostat alone will cause premature wear to an engine due to how much fluctuation occurs between two vehicles during its lifespan. If the history of Bonneville club shows us anything, it shows that a 3800 WILL easily reach in excess of 200,000 miles while running a 180* thermostat the majority of its life. In fact 90% of 3800s on this forum are junked not due to engine failure, but due to body rot, transmission failure, or crash.

Focus your efforts on whats in the forseeable future: the body rot and teh transmission, either way the motor will out last the car. 180*, 195* it doesnt matter.
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Old 02-21-2007, 10:57 PM   #18
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Quote:
Originally Posted by toastedoats
snip... Why cant people just take the advice and knowledge of the thousands of members here and make some use out of it, instead of producing scientific THEORY that doesnt include all of the facts or variables. snip...
Welp, while the rehash gets to be a bit tiresome, sometimes getting a nice reality smack in the face is the only way things get learned.

I can only venture a guess that those who believe that the higher temps are better for the car have never been racing. They have never seen folks with a lot more experience doing everything they can to cool the motor down between runs, etc. etc. And thus have not yet learned that a cold intake manifold is worth more to your ET than all the thermal efficiency calculations combined. Some things just have to be learned. Perhaps a stack of burned up exhaust valves and blown pistons would convince them.

The whole 195 vs 180 vs 160 argument comes down to what you think you can get away with on the sniffer. GM had no choice, the car had to pass emmissions to roll out of the factory, so they selected a 195 operating temp. As the end users, we can bend the rules a little to let the engine live a more comfortable life and put out a little more power with a 180..or strech the limit a little more with a 160. Here in Florida, my car will never have a sniffer stuffed up the tail pipe, so I'll run the 180 in everything, as I always have done. Somebody who has to pass an emmision check can still try it, and they will probably still pass. Either way, no harm has been done to the motor.
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Old 02-22-2007, 01:04 AM   #19
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Geez, I hope there is room for a dissenting opinion in this thread.

No way would someone want everyone to agree with them all the time and would want to surround themselves with "yes men " sycophants would they ?

I had experience in another thread where I came very close to being flamed, someone made an abitrary decision about no longer arguing a certain topic and then another moderator got all sarcastic after the thread in this so called FORUM got locked and as bonus I found out more about Connecticut then I'll ever want to know.

So now I am really convinced by all the kindly delivered comments that it is "go180 or blow"!
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Old 02-22-2007, 01:35 AM   #20
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I'm going to say this again...

Run what you will... 180 or 195... If you are in an Ice cold climate you may want to stick with the 195..

I run the 180 in everything I own as well..

15F is in no way going to make or break a 3800

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