What oil will you use?

[Draco-REX]

Penzoil Platinum. Good HTHS for the price and the BobIsTheOilGuy.com forums like it.

Mobil 1 and Subarus don't go together well. US Castrol is on the thinner side when it comes to HTHS. And considering my planned useage and OCI, Amsoil and RedLine are a bit pricey.

[smbrm]

Originally Posted by Calum

As described, the number before the W indicates the cold viscosity and the number after the W indicates the hot viscosity properties of the oil. Given that this car calls for an oil that has low viscosity at low temperatures, 0W, I would stick with something that also is a 0W. But the Higher number is a little ambiguous. The lower the number is, the more the oils viscosity drops as it gets how. Changing to an oil with a higher number after the W will give you a more temperature stable oil more then anything else. The viscosity at normal operating temperature wont be effected much, but will remain in the correct operating range for the engine for a higher temperature.

I'll be running Mobile 1 0W40.

Sort of. The number after the W does not represent a rate of change of viscosity with temperature.

It does however represent a range of viscosity values at temperatures and conditions that oil producers and engine manufacturers have jointly agreed are relevent to engine operation as it relates to oil thickness. To be listed as say a "30" in an ?W-30 requires that the oil fall within a range of viscosity values for kinematic viscosity of 9.3-12.5 cSt at 100 deg C and have an HTHS(high temperature high shear) dynamic viscosity of greater than or equal to 2.9 mPas at 150 deg C. ?W-20 would be 5.6 to 9.3 cSt and HTHS greater than 2.6mPas.

HTHS dynamic viscosity requirements actually relate to temperatures and oil shear rates in connecting rod bearings as a mechanical point of reference.

http://www.tribology-abc.com/abc/viscosity.htm#dynamic

Scroll down to the table for SAE Viscosity Grades for Engine Oils1 — SAE J300 Dec 99

The industry standards in the above table show the minimum requirements that oil producers and engine manufacturers use for categorizing the flow characteristics of engine lubricants. Engine designers can then design engines knowing what properties to expect from products based on their viscosity grade.

Lower HTHS values have demonstrated better fuel economy, but because the oil is thinner at high temperature, care has to be taken to ensure engines recommending these viscosity grades are appropriately designed to use them. If an engine has been properly designed to use lower viscosity engine oils adequate film thickness should be available from the recommended viscosity grade under conditions specified by the engine manufacturer.

Now if you plan to subject the engine to higher loads and temperatures, than what the manufacturers suggests are normal, as the owners manual in this case suggests, one might want to consider an oil with a higher number after the W. Conceptually, there was however, an old rule of thumb which suggested that you have more potential for wear from an oil that is too thick at low temperture than you would get from one that is too thin at high temperature.

This can get to be a complicated subject rather quickly!

[Wreakin]

I'll go going with M1 0w-30 AFE. I really don't see the use of going with a heavier oil, unless you plan to track every weekend.

[Draco-REX]

For those planning on Mobil 1, keep track of your oil consumption. If you see your engine using a lot of oil, switch to different brand.

[Calum]

Originally Posted by smbrm

a bunch of very true and well worded, good info.

Hey, thanks for the much more complete explanation. First off a disclaimer, I've lost a lot of the finer details in the almost decade since I studied this.

Basically what I was trying to get at was that with the periodic heavy loads that most of us will be subjecting our engines to, an oil with a better VI would be more appropriate. Also, by maintaining an oil with similar cold properties you'll ensure the oil stays within the designed operating range of viscosity, even at normal operating temperature. But, the oil won't be as proned to go out side the designed range of viscosity when we start beating on the car.

[driver01]

Ill probably stick to motul 5w40 for the track and summer time
and 0w20 for winter time, as I understand 0w20 is fully synthetic oil.
for 0w20 ill use the dealer supplied.

[smbrm]

Originally Posted by Calum

Hey, thanks for the much more complete explanation. First off a disclaimer, I've lost a lot of the finer details in the almost decade since I studied this.

Basically what I was trying to get at was that with the periodic heavy loads that most of us will be subjecting our engines to, an oil with a better VI would be more appropriate. Also, by maintaining an oil with similar cold properties you'll ensure the oil stays within the designed operating range of viscosity, even at normal operating temperature. But, the oil won't be as proned to go out side the designed range of viscosity when we start beating on the car.

Glad the info was of help. I can get carried away in the detail having been a formulator for over 30 years.

As you have said, higher VI, simply put, is good. However VI is also a complicated subject when you layer in the effects of temporary and permanent viscosity loss as well as any fuel dilution during use of the oil.

Just for clarity sake when trying to understand low temperature performance what the numbers in the table are telling us is that a

0W?? oil is supposed to guarantee that the oil is thin enough to allow an engine to crank fast enough to start at -35 deg C and thin enough to properly pump at -40 degC.
5W-?? oil is supposed to guarantee that the oil is thin enough to allow an engine to crank fast enough at -30 deg C and thin enough to properly pump at -35 degC.
You want the oil to be thin enough to pump at 5 deg C lower than the oil being thin enough to allow the engine to crank fast enough to start to ensure that the oil gets to all the places its supposed to be!

Some may say it never gets that cold where I live! However the lower low temperature viscosity results in reduced oil drag in the engine, improves oil flow and reduces fuel consumption. Also increases power.

[Calum]

Originally Posted by smbrm

having been a formulator for over 30 years.

Damn! The only thing I've done for over 30 years is breath. I've been in the Navy for 13 years, so far I've been an oiler, fridge tech, heavy equipment tech, Boiler operator, instrumentation tech and now I'm an electronics tech.

Sorry for the off topic everyone.

[smbrm]

Originally Posted by Calum

Damn! The only thing I've done for over 30 years is breath. I've been in the Navy for 13 years, so far I've been an oiler, fridge tech, heavy equipment tech, Boiler operator, instrumentation tech and now I'm an electronics tech.

Sorry for the off topic everyone.

Well I had lots of different jobs but they all were related to engines oil in one form or another.

[dsgerbc]

Anybody knows where Subaru sources their 0w-20 synthetic? Is it any good?

[serialk11r]

Originally Posted by smbrm

0W?? oil is supposed to guarantee that the oil is thin enough to allow an engine to crank fast enough to start at -35 deg C and thin enough to properly pump at -40 degC.
5W-?? oil is supposed to guarantee that the oil is thin enough to allow an engine to crank fast enough at -30 deg C and thin enough to properly pump at -35 degC.
You want the oil to be thin enough to pump at 5 deg C lower than the oil being thin enough to allow the engine to crank fast enough to start to ensure that the oil gets to all the places its supposed to be!

Some may say it never gets that cold where I live! However the lower low temperature viscosity results in reduced oil drag in the engine, improves oil flow and reduces fuel consumption. Also increases power.

I'm pretty sure that's the absolute minimum temperature your car is guaranteed to start. From what I understand, even summer temperatures are too low for the oil to flow well, and the majority of wear occurs on startup and when the engine is still cold, and that doesn't mean cold to the human body

[smbrm]

Originally Posted by serialk11r

I'm pretty sure that's the absolute minimum temperature your car is guaranteed to start. From what I understand, even summer temperatures are too low for the oil to flow well, and the majority of wear occurs on startup and when the engine is still cold, and that doesn't mean cold to the human body

Guaranteed based on the definitions. Unfortunately the SAE viscosity grading system does not have a "grade" to specify performance at lower temperatures than those associated with 0W. However that does not prevent formulation of viscosity values lower than the maximum for the grade's temperature definitions.

Butane is added to gasoline in winter, to assist low temperature starting. Butane has a flash point of -60C. So as long as the front end of the fuel can vapourize(has a low IBP), it has an appropriate distillation curve, the engine oil is thin enough to allow pumping and fast enough cranking to meet minimum start rpm, and the battery retains enough amps an engine can be started at temperatures lower than -35. Actually its usually battery cranking amps loss with temperature decrease that has the greater impact on starting ability.

".....even summer temperatures are too low for the oil to flow well, and the majority of wear occurs on startup and when the engine is still cold..."

Correct to a point but more appropriately stated as: there are benefits from using low viscosity multigrade oils even in summer.

[Memphis]

So for Memphis weather I would it would be best to use 0w-20? What do you guys think of AMS oil?

[NeedsmoreCowbell]

For hot texas summers ? 5w40?