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Super Moderator
2016 3.6 Limited with ES
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2,692 Posts
Discussion Starter #1
The purpose of this thread is to give those who wish to dig a little deeper into oil selection something else to consider. It is not meant to be a gateway to any recommendations but instead a tool to work with given your own circumstances. When people make recommendations about using an oil that may not be strictly condoned by the OM, but based on their own driving situation, the following may be helpful. First a bit of background.

The industry lists cold and hot temp viscosities at two different temps which are 40C and 100C. This is universal by oil producers and companies that do UOAs.

The concern arises when your temp doesn't reach 100C or in some heavy duty uses, exceeds 100C as your normal oil temp.

On my 3.6 the freeway oil temp is around 195 - 197F sometimes around 205 going up a modest grade but did get up to 221 sustained when driving up the grade outside of Vegas with a cargo box, full car, 70 mph and ambient temps of 110. But it's almost always 197 which means that my oil, at my operating temp, is thicker than the 100C temp spec listed by the oil producer. Fortunately, there is an easy way to figure out the viscosity of your oil relative to the listed 100C spec. Here's how.

You will need the following:

1. The Widman operational viscosity calculator found here.

http://www.widman.biz/English/Calculators/Operational.html

2. An F to C temperature conversion calculator unless your car displays C. I used this one.

http://www.rapidtables.com/convert/temperature/fahrenheit-to-celsius.htm

3. The 40C and 100C temp values from the data sheets from whatever oil producer you want to evaluate.

I'm using Castrol 0w-30 in my car so let's run the numbers.

197F is converted and rounded up to 92C. From Castrol's site, the 100C and 40C figures are 12.18 and 73.21. This is a very thick 30w and as you'll see, it's a 40w at my regular operating temp.

Using the Widman calculator the operational viscosity at 92C is 14.57 cSt. That a true 40w oil without any doubt and somewhat thick but the car runs well and mileage is good. I'm happy with that.

If my temp goes up to 220 sustained, the cSt value changes to 11.19, a nice 30w.

But if I run the Pennzoil Platinum 5w-30, that has 100C starting value of 10.3 it changes to a much thinner oil that borders on being a 20w but I'll let you run the numbers to see.

The caveats here are plenty such as viscosity isn't the only thing that provides protection to your engine although we know that thicker oil is recommended if the engine is put under heavy use at high temps. We also know that thicker oils take longer to get up to operating temp so for shorter trips where a thicker oil never really warms up, a thinner oil may be better. Also consider that the oil temp from the car might be from a sensor that obtains data at a cool point in the circulation but it's all the data that Mother Sub gives us.

I have my own conclusions on what a good oil might be given the above but I leave those choices to each driver. Some may not be bothered and others might use the calculator just for the fun of it.
 

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On the Super Mod Squad
2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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26,193 Posts
moved to proper section,

as for me I like quality green European olive oil. and like Oliveri's bar tender type integrated spout.
making sure to not buy more then can be consumed in 6 months. (freshness matters).

 

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Super Moderator
2016 3.6 Limited with ES
Joined
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2,692 Posts
Discussion Starter #3
moved to proper section,

as for me I like quality green European olive oil. and like Oliveri's bar tender type integrated spout.
making sure to not buy more then can be consumed in 6 months. (freshness matters).
Product of a European countriy or produced in Europe? There is a difference.

My oilness transcends cars.
 
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