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#130409 - 04/30/05 06:50 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
moribundman Offline


Registered: 06/02/03
Posts: 23591
the morbid one wwrote:
quote:
quote:Don't forget to test your engine under high load. [Big Grin]
Gary wrote:
quote:
If it will help, I'll flog my minivan. It has 5w-20 in it. [Big Grin] I'll slam it up to the rev limiter for ya!! Heck, I can probably hit the hp peak (if it's still there) of 5000 rpm ..and maybe more.


Then you'll have it! A comprehensive evaluation of thin oil in a "world class" (well, 3rd world anyway) engine. [Big Grin]

Gary, when I said "high load" I meant load and not high RPM! Put your car in second gear and do some rolling starts with full throttle. That's high load! Let's see what your rod and crank bearings will "say." Go high speed and let drag and air resistence cause high load on the engine. Sure, high RPM and high load can occur together, but not likely at the local street-legal speeds.

PS: jtantare, no offense taken. [Wink]

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#130410 - 04/30/05 06:53 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
Bryanccfshr Offline


Registered: 10/09/04
Posts: 5414
Loc: Durango, Co
Remind any one of Japan and the 2 liter gas guzzler tax?

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#130411 - 04/30/05 06:56 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
Craig Offline


Registered: 10/09/04
Posts: 218
Loc: Detroit
Ok here's the other reason for 5W-20.
THE ENGINE HEATS UP FASTER!!

Why do they care? Because all the pollution controls on a
new car do NOT work until the engine is completly to
temp. Not just the water gettng warm and the heater working
but also the oil.

At least here in Michigan, we always had/have oxygenated fuel in the winter. This provides for less air pollution.
The typical short runs to the store in the winter do not get the engine warm enough for the anti pollution stuff to work producing more air pollution.

Simply 5W-20 oil warms up faster than any 30 or heavier oil.

Craig

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#130412 - 04/30/05 07:38 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
G-MAN Offline


Registered: 11/15/02
Posts: 8854
Loc: SC
quote:
Originally posted by Craig:
Ok here's the other reason for 5W-20.
THE ENGINE HEATS UP FASTER!!

Not in my experience. The brief time I ran 10w30 back in the winter that was the first thing I noticed. The automatic climate control on my Chrysler won't let the fan start up on the heater until the coolant reaches 40C. With 10w30 the fan would start blowing warm air much sooner than when I'm running 5w20.

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#130413 - 04/30/05 08:01 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
jtantare Offline


Registered: 04/26/05
Posts: 239
Loc: California
quote:
Originally posted by Craig:
Ok here's the other reason for 5W-20.
THE ENGINE HEATS UP FASTER!!

I think you have it backwards. Thick oil generetes more heat than thin oil. So the engine will heat up faster with thick oil.

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#130414 - 04/30/05 08:12 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
AEHaas Offline


Registered: 01/09/05
Posts: 1312
Loc: Sarasota, Florida
Thicker oils have more internal friction and therefor heat up faster. However, it assumes all else is constant. A thicker, synthetic with more lubricity may have less friction than a poorly formulated dino 20 wt oil.

aehaas

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#130415 - 04/30/05 08:44 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
Mamala Bay Offline


Registered: 02/21/04
Posts: 1988
Loc: USA
It's hard to compare thin & thick with quality synthetic oil because they are thinner to begin with than dino. They flow faster. It runs cooler. Less heat better for the engine longevity.

Given the choice, I would want an oil as with synthetic that cools the engine down far quicker than dino oil. The thinner the fluid, the quicker it cools it down. Now the question remains, how much thinner can you go in wear protection.

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#130416 - 04/30/05 09:03 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
427Z06 Offline


Registered: 12/06/03
Posts: 7409
Loc: Austin, TX
When testing a non-friction modified 15w40 HDEO and a friction modified dino 5w20 in particular engines, my experience has been that when they have non-friction modified 15w40 HDEO in them, they reached operating temperature is less time. My guess is, they were burning more fuel to maintain the same idle and moderate acceleration levels, thus the engines were generating more heat.

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#130417 - 04/30/05 09:35 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
Bryanccfshr Offline


Registered: 10/09/04
Posts: 5414
Loc: Durango, Co
quote:
Originally posted by jtantare:
quote:
Originally posted by Craig:
Ok here's the other reason for 5W-20.
THE ENGINE HEATS UP FASTER!!

I think you have it backwards. Thick oil generetes more heat than thin oil. So the engine will heat up faster with thick oil.
I think thinner oils are able to absorb/transfer heat faster due to the advantage in surface area(I could be visuallizing viscosity wrong but I think of thicker viscosities as having larger molecules or longer chains of them while lighter viscosity would have smaller molecules/shorter chains). Would that not allow the motor oil to warm up faster? [I dont know]

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#130418 - 04/30/05 09:58 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
Mamala Bay Offline


Registered: 02/21/04
Posts: 1988
Loc: USA
quote:
It's hard to compare thin & thick with quality synthetic oil because they are thinner to begin with than dino. They flow faster. It runs cooler. Less heat better for the engine longevity.

Given the choice, I would want an oil as with synthetic that cools the engine down far quicker than dino oil. The thinner the fluid, the quicker it cools it down. Now the question remains, how much thinner can you go in wear protection.

In theory a thinner oil will cool your engine down quicker. But in real world application, wear protection I would assume is the first priority.

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#130419 - 04/30/05 05:25 PM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
TallPaul Offline


Registered: 10/22/03
Posts: 12907
Loc: By Detroit
quote:
Originally posted by Mamala Bay:
It's hard to compare thin & thick with quality synthetic oil because they are thinner to begin with than dino.

Actually I don't think this is true in the strict sense of the word thinner. A 10.5 cSt synthetic is just as thick as a 10.5 cSt dino. The synthetic does flow better and in a sense is thinner in that it has a much narrower molecule size distribution, or so I seem to recall.

Rather than risk a thin 5w20, I would go synthetic 10w30.

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#130420 - 04/30/05 05:57 PM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
AEHaas Offline


Registered: 01/09/05
Posts: 1312
Loc: Sarasota, Florida
And this is why oil is so difficult. At 100 C two oils may have the same viscosity. The same oils may differ widely at 10 C and below and may differ widely at 150 C and above. This is why we have to compare viscosity only at a certain temperature.

The viscosity can also be defined by the application. My Ferrari runs much cooler with the 20 wt Mobil 1 than the 40 wt Shell Helix Ultra. My operating viscosity is about the same as the "thicker" oil at the higher temperature. My oil is NOT thinner driving to work than with the 40 wt oil. I get about the same pressures with either oil.

aehaas

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#130421 - 04/30/05 07:31 PM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
quote:
The viscosity can also be defined by the application. My Ferrari runs much cooler with the 20 wt Mobil 1 than the 40 wt Shell Helix Ultra. My operating viscosity is about the same as the "thicker" oil at the higher temperature. My oil is NOT thinner driving to work than with the 40 wt oil. I get about the same pressures with either oil.

I'm trying to sort out some observed data and will probably be left with more questions. We assume that thinner oils more easily uptake btu's ..which follows with our normal perceptions of other common observations. What we don't know (or at least I have trouble defining) is whether the apparent oil temps that we see, either higher or lower, are the function of heat uptake/rejection or interactive properties that promote heat creation.

That is, if we accept that thinner oils uptake and reject heat better than thicker oils ..fine. That belief sort of mandates that you also would assume that thicker oils would always be lower in temp since their uptake of btu's would be reduced. You sorta can't have one school of thought without adopting the other (there's naturally more to this ..but let's save space). So we have to also consider that there is some reactive/interactive component that is in place besides simply heat transfer characteristics. Does oil viscosity merely reflect/indicate conditions temperature-wise, or does it cause it???


We commonly see many applications where a "lubricant" is more of a coolant. Industrial compressors/blowers, automatic transmissions, etc. where the actual lubricant has little tolerance for high shear/high stress conditions beyond a narrow temp/flow range.

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#130422 - 05/01/05 09:57 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
jtantare Offline


Registered: 04/26/05
Posts: 239
Loc: California
quote:
Originally posted by AEHaas:
And this is why oil is so difficult. At 100 C two oils may have the same viscosity. The same oils may differ widely at 10 C and below and may differ widely at 150 C and above. This is why we have to compare viscosity only at a certain temperature.

The viscosity can also be defined by the application. My Ferrari runs much cooler with the 20 wt Mobil 1 than the 40 wt Shell Helix Ultra. My operating viscosity is about the same as the "thicker" oil at the higher temperature. My oil is NOT thinner driving to work than with the 40 wt oil. I get about the same pressures with either oil.

aehaas

It would make a lot more sense to show oil viscosity specs as a curb on a temp vs cSt graph rather than just 2 data points at 40 and 100 C and extrapolating a VI from those 2 points.

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#130423 - 05/01/05 02:42 AM Re: I am tired of everybody saying 20 wt oils exist only for gas mileage
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
quote:
Gary, when I said "high load" I meant load and not high RPM! Put your car in second gear and do some rolling starts with full throttle. That's high load! Let's see what your rod and crank bearings will "say." Go high speed and let drag and air resistence cause high load on the engine. Sure, high RPM and high load can occur together, but not likely at the local street-legal speeds.
Well, would 75 in a minivan climbing the mountains of central PA on I-80 qualify?? I don't think my oil temp broke 160F. Granted I haven't done any "Fast and Furious" action in my minivan ..but [I dont know] .

(visions of the black vantriliquist on Police Academy 3, with Taiwanese Kung-Fu movie poor lipsynch):
"I will accept your challenge!" [Dual]

The minivan ..so obedient ..so docile ..so unnoticed ..so under estimated...it asks no praise ..and makes no apologies. [Big Grin]

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