Using GF-7A instead of GF-7B...

[phantomxj]

Greetings, everyone.

I came here asking a question because I emailed a number of other sources but got no answer back.

I am from Iraq and I own a Chinese-spec Toyota Corolla Hybrid with 8ZR engine. This engine is basically the same as the 2ZR engine. In the summer here, it can get really hot, reaching 50°C (122°F), and I drive about 4,000km (about 2,500mi) every month, which includes a lot of uphill driving.

I am currently using 0w-16 oil but I want to switch to 0w-20. In the manual, it does mwntion that I can use a thicker oil for more protection for these extreme driving conditions... but I noticed that all viscosities higher than 0w-16 are GF-7A while the original viscosity recommended to me is GF-7B. I am curious because I read that this B classification was made for engine with very tight clearances and this got me concerned. Will a GF-7A oil liks 0w-20 cause long-term damage?

 

[phantomxj]

Oh. A hybrid. I would probably run the 0w-20. Perhaps the engine does not run constant or long enough to get and hold a operating temp of over 210F to really warm the 5w30. Ow20 should be good restore protect .

Thanks, I'll stick to 0W-20 for now. You guys have been really helpful. I'm glad I came here.

 

[kschachn]

Yes, but then everyone kept reply with a new piece of information and... well, curiosity got the better of me.

Like I said.

 

[kschachn]

Oh. A hybrid. I would probably run the 0w-20. Perhaps the engine does not run constant or long enough to get and hold a operating temp of over 210F to really warm the 5w30. Ow20 should be good restore protect .

Again, heavier oils warm up faster.

 

[phantomxj]

Again, heavier oils warm up faster.

I'll switch to a 20 grade for now and if I notice that the engine is still rough when running, I'll consider a 30 grade oil... but I'm curious, how faster will a 0W-30 warm up when compared to a 0W-20 oil? I'm interested because it's a hybrid and I can't just sit around and wait for the engine to warm up, I just start and go but take things slowly till it gets kinda warmed up.

 

[Durdude]

Again, heavier oils warm up faster.

Oh. I have not heard that. Why is this?

 

[JohnnyG]

Thanks, I'll stick to 0W-20 for now. You guys have been really helpful. I'm glad I came here.

Just like the song, "Hotel California"
You can come here any time you want, but you can never leave.....

 

[phantomxj]

Just like the song, "Hotel California"
You can come here any time you want, but you can never leave.....

I kinda do like it here. Everyone has been really helpful, and seems to know their... oils.

 

[JohnnyG]

I kinda do like it here. Everyone has been really helpful, and seems to know their... oils.

And a LOT more.

 

[ZeeOSix]

Oh. I have not heard that. Why is this?

Thicker oil has higher film shearing friction if the oil film is being sheared between moving surfaces. But a thinner oil between the same two moving surfaces gives a thinner operating oil film thickness, which increases the shear rate in the thinner oil which also increases the heating. So if both oils are being sheared between the two same moving surfaces at the same speed, then their heating rates will cancel out to some degree because of the film thickness and shearing rate difference in the two resulting oil film thicknesses.

The shear rate going up as the film thickness goes down is also why tighter bearings run hotter with the same viscosity oil as the bearing clearance decreases. Tighter bearings run hotter than looser bearings when using the same oil viscosity.

The heat up difference between a 0W and 5W isn't worth worrying about, especially in a warmer climate. And the heating difference between a KV100 grade of 20 vs 30 is even more negligible.

 

[phantomxj]

And a LOT more.

Hey, knowledge is power, you know?

 

[kschachn]

Thicker oil has higher film shearing friction if the oil film is being sheared between moving surfaces. But a thinner oil between the same two moving surfaces gives a thinner operating oil film thickness, which increases the shear rate in the thinner oil which also increases the heating. So if both oils are being sheared between the two same moving surfaces at the same speed, then their heating rates will cancel out to some degree because of the film thickness and shearing rate difference in the two resulting oil film thicknesses.

The shear rate going up as the film thickness goes down is also why tighter bearings run hotter with the same viscosity oil as the bearing clearance decreases. Tighter bearings run hotter than looser bearings when using the same oil viscosity.

The heat up difference between a 0W and 5W isn't worth worrying about, especially in a warmer climate. And the heating difference between a KV100 grade of 20 vs 30 is even more negligible.

And the winter rating has little to do with it.

 

[ZeeOSix]

And the winter rating has little to do with it.

My point was if you're starting up a cold engine the 5W will typically be thicker than a 0W at the same cold temperature, and theoretically warm up a bit faster in the early stages of engine warm-up due to the higher shearing friction of the thicker oil, but again the difference is basically splitting hairs. There are all kinds of heat transfer factors going on inside a running engine that can add-up or cancel each other out. In the end, the difference is way smaller than most people think. Once the oils are near and at full operating temperature the in-bearing film thickness temperature rise is pretty negligible between a KV100 20 and 30 grade due to the running MOFT factor.

 

[ZeeOSix]

Here's some test data showing the temperature rise difference between a 0W-20 and 0W-30 with the oil supply at 90C. Unknown what the bearing clearance was, but I'd assume normal factory clearance. The temperature rise difference at 4000 RPM is only 1.5C in the bearing. Higher RPM of course also causes a higher temperature rise. At low RPM the difference is only about 1C.

 

[berniedd]

In the toyotaownersclub forums, 5W-30 is well recommended for 2ZR engines, especially in hot climates. I would go with that. Heck, I might even go with 5W-40 if I lived in your climate that goes 50 degrees C.

 

[Japanese]

In the toyotaownersclub forums, 5W-30 is well recommended for 2ZR engines, especially in hot climates. I would go with that. Heck, I might even go with 5W-40 if I lived in your climate that goes 50 degrees C.

That's true but he saiid his is a hybrid.

 

[berniedd]

Right. It's a hybrid, but he says he does a lot of hill climbing, which I take will keep the engine running for quite some time.

 

[phantomxj]

In the toyotaownersclub forums, 5W-30 is well recommended for 2ZR engines, especially in hot climates. I would go with that. Heck, I might even go with 5W-40 if I lived in your climate that goes 50 degrees C.

That's a bit too thick and above the maximum recommended viscosiry in the manual, but if 0w-20 proves to be still too thin, I might switch to 0w-30 to make the engine even quiter and smoother.

 

[phantomxj]

Right. It's a hybrid, but he says he does a lot of hill climbing, which I take will keep the engine running for quite some time.

Correct, uphill driving keeps the engine on for longer but I don't find it that concerning. I drive a lot on the highway which also keeps the engine on. The engine was fine in 0W-16 but boy, it sounded rough.

 

[phantomxj]

I switched to 0W-20 for now because I could hear the high-pitched noise of the engine on those uphill drives with 0W-16, and it is better now with the new oil. Temps are currently in the 30—45°C range, once we get close to 50°C, I'll check the engine sound again on the same uphill drives and then decide if 0W-30 is needed. Thanks everyone, I appreciate all the responses and I learned so much from you all, especially @ZeeOSix, you are a hero.