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CougarXR/7
12-21-2016, 06:52 PM
Ok.......I have over 210 thousand on my 94' SC...............I use Castrol High Mileage 5/20 grade oil.................no problems. So........just wondered if anyone uses STP to get some extra protection?

KMT
12-21-2016, 08:00 PM
Any leaks?

If that castrol hi mile mean 'extended use' or for high mile cars?

Some reason you've not been running the factory recommended 5/30?

But no, I don't bother w/STP on my 110k Anny. Mobil1 5/30 hi mile. Doesn't use/burn/lose oil between changes, so...

CougarXR/7
12-21-2016, 11:03 PM
I use the high mileage.no leaks or burning oil.........just curious if anyone used STP. Back in the Muscle Car days..........I added it every oil change. 5/20 for those below zero days here in the Chicagoland area.

davec73
12-21-2016, 11:35 PM
Restore engine treatment is the best product to use in high mileage engines. Stop is a terrible product to use for modern motors with small oil galleys.

racecougar
12-21-2016, 11:51 PM
A 0W-30 would make far more sense regarding cold ambient temps than a 5W-20. :confused:

TBirdJKC
12-22-2016, 03:06 AM
A 0W-30 would make far more sense regarding cold ambient temps than a 5W-20. :confused:

Yeah, I always understood that first number was the thickness of the oil "cold," and the second number was the actual viscosity at operating temp. So 0W-30, 5W-30, and 10W-30, would all be the same once up to temperature, but 5W-20 would be all around too thin compared to 5W-30. Correct? I've never run anything but what the manual calls for in any of my vehicles.

racecougar
12-22-2016, 10:19 AM
That is correct.

Tim Groth
12-22-2016, 02:27 PM
My '89 w/ 232k on the clock runs any brand of synthetic oil. It leaks and burns oil so usually whatever is the best price point at the time. Never have bothered with any additional additives.

Weight is usually 5w/30 or 10w/40

-Tim

Rotaryeccentric
12-22-2016, 07:42 PM
I've driven my SC all winter long for the past 6 winters in Salt Lake City. 5W-20 is what I use in the winter because I can have cold morning starts as low as 5*.

The funny thing is that 5w-20 actually has a lower 40*C viscosity than 0W-30. Castrol's product sheet lists 5W-20 as 49.35 mm˛/s at 40C. 0W-30 is basically the same but a slight bit higher at 51 mm˛/s.

So, buy what's available or on sale :)

racecougar
12-23-2016, 12:19 AM
The funny thing is that 5w-20 actually has a lower 40*C viscosity than 0W-30. Castrol's product sheet lists 5W-20 as 49.35 mm˛/s at 40C. 0W-30 is basically the same but a slight bit higher at 51 mm˛/s.

Of course it does. 40C = 104F which is smack dab in the middle between the temps for the "W" and standard grading (0F and 212F).

racecougar
12-23-2016, 12:20 AM
This should probably be posted here: https://bobistheoilguy.com/motor-oil-101/

Rotaryeccentric
12-23-2016, 06:38 PM
Of course it does. 40C = 104F which is smack dab in the middle between the temps for the "W" and standard grading (0F and 212F).

True, true. So this is where things confuse me. I need your help on this one. The Castrol product sheet gives a different viscosity unit for the below freezing figure, in mPa.s (cP) - whatever that is

0w-30 they run at -35C
5w-20 they run at -30C

0w-30 comes out to 4600 mPa.s (cP) at -35C
5w-20 comes out to 4300 mPa.s (cP) at -30C

Are those close? Is that a reading for how thick or "difficult" the oil is on things at winter startup? Am I reading any of this right to begin with? Should I even be reading any product sheets to begin with? :)

It seems like they are relatively close numbers to me and that's why I decided they are pretty close oils, because the numbers match well at below zero, at 40C, and at 100C - (its like 9 mm2/s for 5w-20 vs 9.5 mm2/s for 0W-30 at 100C)

The boboilguy page is really insightful, but it looked like his examples are at 75*F and it seems like that is closer to the 40C rating than what true winter conditions are like for me.

Anyway, sorry if this is overkill of a simple question, but trying to tell how far it matters.

Appreciate the help!

racecougar
12-24-2016, 04:16 PM
Could you post up a link to the data sheets you're looking at? The ones I've found for those weights are showing different values (for example: 5800 centipoise at -35C for 0W-30 Castrol Edge)?

To make a direct comparison, the oils should be tested at the same temperatures. 300 cP is a noticable difference in viscosity.

And no problem. I enjoy the discussion.