5w30 or 10w30 - which one to use

[JAG]

Originally Posted By: CompSyn
Well, I know the question is in regards to 5w30 or 10w30, but my answer is neither. Get 0W-30. Better start-up protection.
If startup happens at really cold temps and the additive packages are equally good at preventing wear in those conditions, then that's true. Otherwise, the claim does not hold.

Originally Posted By: CompSyn
Better fuel economy.
Again, same type scenario as for cold flow. It depends on many things so the claim does not hold. One example: I've used Castrol 0w30 and many XW-40 oils in my VW. The oil that gave the worst gas mileage overall was Castrol 0W-30.

Originally Posted By: CompSyn
I personally use AMSOIL Signature Series 0w30, good stuff.
Yes it is good stuff. Good and expensive.

 

[Steve S]

It really won't matter which oil you choose.

 

[FrankN4]

JAG
Help me to understand. I copied all the below some time ago after doing a Google on viscosity:

"For the purpose of lubrication, viscosity has been since the beginnings of Lubrication Engineering held as the most important quality of the Lubricant.

The reason for this is that if the lubricant is too thin, it gets forced out from bearing surface under pressure and poor lubrication occurs, this leads to bearing surface damage.

For example Motor Oil that is measured to have viscosity of 9.5 cSt @ 100 C will be rated as SAE 30, while another Motor Oil that is measured to have viscosity of 12 cSt ( or 26% more viscous ) will also be rated as SAE 30 Motor Oil.
Yet in real life operation 26% difference in viscosity may make difference between engine that will run forever and one that will wear out prematurely.

No matter what oil you use for any purpose the ideal viscosity that provides the ultimate lubrication, that is TOTAL bearing surface separation, and at MINIMUM power that is consumed by the lubricants viscosity (MINIMUM TEMPERATURE RISE) occurs ONLY at ONE combination of:
SPEED
LOAD
TEMPERATURE

Under ALL other combinations of the three factors, the lubricant is NOT IDEAL."

THE BELOW IS FROM ABOUT 2004 AND MAY BE UPDATED BUT IT SHOWS ORIGIONAL THOUGHT.

"Thinner motor oils such as 5W-20 or even 0W-20 are becoming more popular these days and are even specified by some OEM's (FORD & HONDA)
Although these oils are promoted as "energy conserving" they generally trade a gain of less than 0.1 MPG in Corporate Average Fuel Economy (CAFE) for shorter useful engine life.

FORD which has previously designed cars to have 10 year or 150,000 miles life has reduced the mileage life expectation to "beyond 100,000 miles" on vehicles that are operated on SAE 5W-20 Motor Oil.

HONDA only claims "useful life" as 7-years or 70,000 miles in EPA certifications for their CIVIC which uses SAE 5W-20 Motor Oil, while the previous model that utilized SAE 5w30 Motor Oil was certified for 10 year or 100,000 mile durability.
By contrast Mercedes-Benz recommends use of ONLY Synthetic Motor Oil that is at least SAE 5W-40! This is a recent increase in recommended viscosity from SAE 5w30. Apparently customer research indicated that engine longevity is more important to typical MB customer than fuel economy.

Even more important is the High-Shear High-Temperature MINIMUM specification in SAE J300. In tables below you will notice that there are "two" SAE 40 specifications, one with minimum HSHT value of 2.9 cP for Automotive Oils (SAE 0W-40; 5W-40; 10W-40) and the other for Heavy Duty Oils (HDO) (SAE 15w40; 20W-40; 25W-40; 40).

This double specification is at insistence of heavy duty engine manufacturers who have required HSHT viscosity limits consistent with good engine durability in high-load, severe service operation. HSHT value of 3.7 cP or 27% more viscous oil at 150ºC (300ºF).

Yes, a 27% increase in viscosity makes a difference between Automotive engine that lasts 100,000 miles and Truck engine that lasts 1,000,000 miles."

My truck engine is an American "Bubba" engine; cast iron block V, in block cam, pushrod, rocker arm, 2 valves per cyl. It might possibly see 3000 rpm on extremely rare occasions. There is a realistic possibility that it will go through its projected service life of 200,000+ miles without ever going to 3000 rpm. It will see 70 MPH, about 1700 rpm, but never faster. It will haul a full camping compliment over the Smokey Mountains of TN and NC 3 to 4 times a year, 78F to 100F.

From the above site, they also said that engines that run at lower RPM need a thicker oil than engines that run higher RPM. They said engines that have oil temperatures higher than the 100C/212F need a thicker oil. They said engines that are heavily loaded need a thicker oil.

If I had a 30 grade, 5W or 10W, that had a HTHS of 3.5 and a 40 grade, 5W or 10W, that had a HTHS of 3.0, would my engine be better protected by the 5w30? What if the oil temperature hit 230-240F? I actually use a 15W-50 that has a 100C cSt of 18 and a HTHS of 4.56. Why would it not be better to use an oil that had both a high HTHS(3.7 or better) and a high 100C cSt(12.5 or better) Please, this is a real question, not a response. I don't know. I do know that 15W-50 has taken everything we own which includes a Chrysler van that called for 5W-20, now about 114,000 miles, to compacts with DOHC 4 cyl that sometimes see 6000 rpm, well over 100,000, to my Toyota which called for 10w30, now at 300,000, to my Cavalier, which called for 5w30, to just over 203,000. Was it the viscosity or the HTHS that gives such long life to these engines? I am thinking either viscosity or a combination of viscosity and HTHS.

 

[ARB1977]

5W30 or even a 0W30, ran it in the Tacoma and now in the Jetta (0W30).

 

[JAG]

Originally Posted By: FrankN4

JAG

No matter what oil you use for any purpose the ideal viscosity that provides the ultimate lubrication, that is TOTAL bearing surface separation, and at MINIMUM power that is consumed by the lubricants viscosity (MINIMUM TEMPERATURE RISE) occurs ONLY at ONE combination of:
SPEED
LOAD
TEMPERATURE

Under ALL other combinations of the three factors, the lubricant is NOT IDEAL."

Very true.

Originally Posted By: FrankN4
THE BELOW IS FROM ABOUT 2004 AND MAY BE UPDATED BUT IT SHOWS ORIGIONAL THOUGHT.

"..."

I replaced its contents with dots for brevity. That info. did not seem like accurate info. to me.

Originally Posted By: FrankN4
My truck engine is an American "Bubba" engine; cast iron block V, in block cam, pushrod, rocker arm, 2 valves per cyl. It might possibly see 3000 rpm on extremely rare occasions. There is a realistic possibility that it will go through its projected service life of 200,000+ miles without ever going to 3000 rpm. It will see 70 MPH, about 1700 rpm, but never faster. It will haul a full camping compliment over the Smokey Mountains of TN and NC 3 to 4 times a year, 78F to 100F.

From the above site, they also said that engines that run at lower RPM need a thicker oil than engines that run higher RPM. They said engines that have oil temperatures higher than the 100C/212F need a thicker oil. They said engines that are heavily loaded need a thicker oil.
Yeah, less speed between parts decreases film thickness and a more viscous oil may increase it. Higher oil temperatures reduces viscosity. Using more viscous oil may increase oil temperature but not enough to bring its viscosity down to a less viscous, cooler oil. Yeah, higher loads decreases film thicknesses.

Originally Posted By: FrankN4
If I had a 30 grade, 5W or 10W, that had a HTHS of 3.5 and a 40 grade, 5W or 10W, that had a HTHS of 3.0, would my engine be better protected by the 5w30? What if the oil temperature hit 230-240F? I actually use a 15W-50 that has a 100C cSt of 18 and a HTHS of 4.56. Why would it not be better to use an oil that had both a high HTHS(3.7 or better) and a high 100C cSt(12.5 or better) Please, this is a real question, not a response. I don't know. I do know that 15W-50 has taken everything we own which includes a Chrysler van that called for 5W-20, now about 114,000 miles, to compacts with DOHC 4 cyl that sometimes see 6000 rpm, well over 100,000, to my Toyota which called for 10w30, now at 300,000, to my Cavalier, which called for 5w30, to just over 203,000. Was it the viscosity or the HTHS that gives such long life to these engines? I am thinking either viscosity or a combination of viscosity and HTHS.
In the early days of motor oil there were only straight weight oils and there was no need to do HTHS tests because it was nearly linearly related to kinematic viscosity at 100C. IOW, they could be equated by a simple constant. Viscosity index improvers were developed which causes this simple relationship to not hold. Oils with them have viscosities that depend on shear rate (among other variables as do straight weight oils). They increase kinematic viscosity more than HTHS viscosity; an oil without them having same kinematic viscosity at 100C as one with them will generally have a higher HTHS.

I wish I had more time to answer all of your points/questions, so if I didn't answer sufficiently, I recommend you read the threads in the Interesting Articles forum.