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Discussion Starter #1
My car is corolla 2003 se saloon auto. The car has an stock engine 3ZZ FE but vvti is not enabled in this engine in my country from factory (Pakistan). The odo is 161k KMs. Using 20w 50 for a long time because of stupid mechanics here as they think if the engine crosses 100000 km shift to thicker oil. Now if I want to shift to oem recommended oil
Will I face any problem?
Also I am getting very low fuel economy around 5km per liter (11 US mpg)
On next oil change should I go to 10W40 then 5W30?

Thanks
284476
 

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Just switch. You will be fine. Any leaks will be because the engine already had a leak point
 

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2007 Corolla S
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Because of your temperatures in your country I would suggest a full synthetic lighter weight oil vs conventional oil. I assume thats why they get away with such high viscosities in the first place.

The only reason we see a 50 weight oil in place of a 5w30 in north america is usually someone covering up rod knock etc lol.
 

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Discussion Starter #6
Because of your temperatures in your country I would suggest a full synthetic lighter weight oil vs conventional oil. I assume thats why they get away with such high viscosities in the first place.

The only reason we see a 50 weight oil in place of a 5w30 in north america is usually someone covering up rod knock etc lol.
But is it not bad for the engine this much thick oil. Also where I live high's are 40°C and low's are 10°C
Also economy is bad also bad because of this?
 

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2007 Corolla S
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Because you do not have VVT and when temps are 40c I don't think 20w50 is hurting anything per se. But I agree with you wanting to drop down to a lower viscosity. Especially when it is 10c.

As for economy, viscosity does make a difference for sure. But with that economy you posted I doubt that will correct it. Start there and see how much of a difference it makes.
 

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Discussion Starter #8
Because you do not have VVT and when temps are 40c I don't think 20w50 is hurting anything per se. But I agree with you wanting to drop down to a lower viscosity. Especially when it is 10c.

As for economy, viscosity does make a difference for sure. But with that economy you posted I doubt that will correct it. Start there and see how much of a difference it makes.
Should I shift to 10W40 ? Or 5W30?
 

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Discussion Starter #10
Just switch. You will be fine. Any leaks will be because the engine already had a leak point
May as well just go 5w30. But like I said a full synthetic will handle your temps better in my opinion.
I want to confirm this theory that this much thick oil in any weather condition is bad for the engine because new corolla owner's manual in Dubai condition is recomming 5w20 and here also but toyota dealership is pouring 5w50 against the recommendation in the owners manual. In our country's forum like this people are raising voice against them. I want your opinion on this that thicker oil is bad for our engines
 

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In my opinion a 50 weight is too thick for most smaller engines. The main reason Toyota switched from 5w30 to 5w20 and now 0w20 in some models was for emissions and fuel economy.

Newer cars are being built with such small oil clearances. That thick oil has to jet through tiny bearing feed holes the same way the lighter oils do. So while it appears no immediate damage is occuring I do share your concern.

The only cars I see that recommend that high of viscosities are diesels and high output turbo/supercharged engines. I think I saw a BMW m3 with a 20w60 label on its oil cap. And that was a vehicle built for US market.
 

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Discussion Starter #12
In my opinion a 50 weight is too thick for most smaller engines. The main reason Toyota switched from 5w30 to 5w20 and now 0w20 in some models was for emissions and fuel economy.

Newer cars are being built with such small oil clearances. That thick oil has to jet through tiny bearing feed holes the same way the lighter oils do. So while it appears no immediate damage is occuring I do share your concern.

The only cars I see that recommend that high of viscosities are diesels and high output turbo/supercharged engines. I think I saw a BMW m3 with a 20w60 label on its oil cap. And that was a vehicle built for US market.
So if a car running on a thicker oil for almost 50k kilometers. If I switch to thin oil will there be any problem I will face?
 

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So if a car running on a thicker oil for almost 50k kilometers. If I switch to thin oil will there be any problem I will face?
As mentioned, switch to full syn. 5W/30 if u can get it. It want hurt the eng. Just beaware on hi mileage eng, oil leaks can occur when switching from conventional to syn oil. Dosen't mean it'll happen to yours, just occasionally check o. level & look for any seepage at v.cover, oil pan, filter housing etc. Syn is ALOT slippery VS conventionl oil.
Hopefully mpg will increase, but remains to be seen. Good luck.
 

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Just switch. You will be fine. Any leaks will be because the engine already had a leak point
^^That^^

But is it not bad for the engine this much thick oil?
I think it is bad, although your engine is running OK, so....... The recommended oil viscosity for the 3ZZ-FE according to a chart I found is 5W-30 or 10W-30. So 20W-50 is WAY out of range for this engine. See copy of chart below:

3ZZ-FE Recommended engine oil5W-30
10W-30

Also where I live high's are 40°C and low's are 10°C
Where I live in South Texas the high temps in the summer can be 42-43 Celsius, but usually around 36 C, so it's very similar to your weather. No problem using 5w/30 oil on my 1ZZ-FE with 381K miles. I've always used 100% synthetic or full synthetic, but even a very good non-synthetic oil will do just fine with frequent oil changes.

Also economy is bad also bad because of this?
20w/50 is going to give you bad gas mileage because the oil is so thick, the engine has to crank harder against the oil's resistance. You will definitely get better gas mileage with either of the recommended oils, but you may still have some other issue with your poor mileage, which could be a number of different things. Try one of the recommended oil viscosities and observe your gas mileage and then go from there.
 

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I am very impressed. Have you ever overhauled this engine and how you have maintained this engine till this much km? In Pakistan, people will not even believe it because of stupid mechanics here.
It's 381K Miles = 613K Kilometers! No overhaul of the engine or transmission. In fact, no internal mechanical repairs have been done at all on the engine or transmission (I've replaced the valve cover gasket and the front main oil seal). How have I maintained this car? By doing oil and filter changes (including engine air filter) on a regular basis. This includes transmission fluid exchanges along with radiator coolant exchanges, along with other maintenance. All the cooling system components are original. Now......for some reason I've been lazy with not washing the outside of my car, so the paint looks bad (but I don't care).
:D
 

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When you switch oil to a thinner viscosity, and you find yourself adding oil between oil changes, then that's a key indicator of oil loss.

Give it some time. Too early to say for sure if you are losing oil just based on the images you posted.
 

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Discussion Starter #20
When you switch oil to a thinner viscosity, and you find yourself adding oil between oil changes, then that's a key indicator of oil loss.

Give it some time. Too early to say for sure if you are losing oil just based on the images you posted.
Currently I haven't switched to thinner viscosity. This images are before and after driving only 250 kms on 20w50
 
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