Ambient Temp and Oil Temp?

[Gene K]

1. In a modern water cooled gasoline pc engine what is the average difference in oil temps between 100*F and 0*F?

2. How much difference can you expect in minimum viscosity?

3. Is a 5W-40 (14.0 cSt @ 100C) any thicker at 212*F than a 5w30 (10.5 cSt @ 100*C) is at 190*F?

I know in a Heavy Truck Diesel with a real oil temp gauge it rises 30*F from 180*F to 210*F with a 100*F change in ambient temp.

I'm really interested in why there are not different lubricant suggestions for different temp ranges any more.

 

[LouDawg]

Quote:

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1. In a modern water cooled gasoline pc engine what is the average difference in oil temps between 100*F and 0*F?

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Uhhhh, 100 degrees?

JK...couldn't resist!

I'll let the experts weigh in now.

 

[Gene K]

Calrification:
1. In a modern water cooled gasoline pc engine what is the average difference in peak sustained oil temps between 100*F and 0*F ambient temperature?

 

[Bryanccfshr]

First off to make the Degrees symbol hold down the Alt key and pres the numbers 248. Then you can type 100°.

Of course ambient oil temperature will have an effect on the final oil temperature. Alot depnds on the cooling systems designed in the engine. Those without any oil coolers will show the most variation with ambient temperature. Those with air to oil coolers will have reduced variation while engines with oil to coolant type exchangers will maintain the most consistant oil temperatures in regards to ambient air.

To determine what you are asking use our Bolivian members viscosity curve page he posted for us to use. Pull the 40° and 100°C viscosities of the oils in question off of a PDS and see where theyare at the temperatures in question. Here is the Widman chart.

 

[Bryanccfshr]

To answer directly if the 5w40 has a 40°c viscosity of 77cSt then the 5w40 would have a viscosity of 11.5 at 230°f. to get as thin as the 5w30 is at 212°f it would need to be nearly 240°f.

 

[Gene K]

Degree symbol shortcut doesnt work with my operating system. It can be done, but it is a pain.

 

[dwendt44]

To get the ° symbol, hold ALT key down and type 0176.
That's a zero.
Number lock is ON.
Under 'Accessories' on you program list find 'system tools', then look for 'Character Map'.

 

[moribundman]

Silly PCs. The degree symbol is done with shift+option+8: °

 

[Bryanccfshr]

Or a technically challenged individual could create a document titled "symbols" keeping it handy while browsing and copy the ° out of this thread and paste it in there for use when they needed it.

 

[Gene K]

Since they changed the forum software I cant even get it to work using html. When I press Alt on the keboard it "freezes" the keyboard. No "option" key on my board. Cut and Paste is the only option that seems to work.

BTW I am using an old Redhat version of Linux and a Pre-Firefox Mozilla Browser.

 

[mdv]

05 Tundra with an Autometer oil temp. gauge. Typically, above freezing oil temps run around 180 in town and between 195-210 on highway. 225-240 when towing. Below freezing, oil runs 160-180 and will creep up to 195 if on highway for more than 20 miles.

Anyone have the link to the viscosity calculator that someone here created?

 

[TeeDub]

I used to see a difference of of 10F-15F in average oil temps in my old Audi between summer (85F-100F) to winter (15F-30F).

It still makes technical sense to go up and down one SAE grade, depending on ambient temps. As a general rule of thumb, a reduction of 10C/18F in oil temps is roughly equal to going up one SAE grade in terms of oil pressure and oil film thickness in the valvetrain.

For example, in an OTR truck,you could switch between the Amsoil 15w40/AME and 10w30/ACD every six months. In gas engines, you could switch between a 5w-20 and 10w30 if you were running a conventional oil.

The main reasons for going to a thinner oil in cold weather are easier starting and better fuel efficiency. Provided the oil is thin enough to allow the engine to start reasonably easily, it will be thin enough to prevent excessive startup wear.

 

[427Z06]

Quote:

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1. In a modern water cooled gasoline pc engine what is the average difference in oil temps between 100*F and 0*F?

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Will vary with various engines, especially if one has an oil cooler.

Quote:

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2. How much difference can you expect in minimum viscosity?

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See above

Quote:

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3. Is a 5W-40 (14.0 cSt @ 100C) any thicker at 212*F than a 5w30 (10.5 cSt @ 100*C) is at 190*F?

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Need to know the VI, but using Visc and VI of current formulations, a little.

http://www.geocities.com/CapeCanaveral/3655/VI.html

Quote:

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I know in a Heavy Truck Diesel with a real oil temp gauge it rises 30*F from 180*F to 210*F with a 100*F change in ambient temp.

The concept of changing oil grades for ambient temps is an old one stemming from the use of single-grade oils back in the day.

I'm really interested in why there are not different lubricant suggestions for different temp ranges any more.

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Pull up Widman's chart. Take a step back and look at it. Notice that at the high temperature end, there very little difference between the grades relative to each other. And when you go beyond that chart, you get into HTHS territory.

Big rigs may spend a large percentage of time at WOT. How much time, percentage-wise, can you spend at WOT on a public street or highway in your car/truck/SUV?

Depending on engine design, a thicker oil may end up running at a higher temperature, thus negating most of it's additional viscosity.

The concept of changing oil grades with ambient temps originated back when single grades were the norm.

 

[Steve S]

Feul mileage considerations .

 

[Steve S]

The engines have oil coolers