Toyota’s stance on using a heavier weight oil

In my manual it says a heavier weight oil can be used when operating under heavy load or high speed
Removed from my 2026 Prius and oil grade change as well from 16 to 8.

2025

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2026

2026.webp
 
i could see bearing surface areas being larger in a small engine, and perhaps therefore a lighter oil could be tolerated.............using a thicker oil would still be a plus.
 
Removed from my 2026 Prius and oil grade change as well from 16 to 8.

2025

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2026

View attachment 338212
Regardless of the verbiage change, it is still incredibly difficult for Toyota argue you can't use an oil with higher viscosity under high speeds or extreme load conditions.

In other words, the verbiage has changed but the engine and the benefits of thicker oil have not.
 
I have some 7.5W-40 Amsoil frankenbrow running in my 2019 0W-20 Tacoma. It's not winter anymore, but my MPG's have improved a tiny bit. I am pretty sure I could be dreaming and 19mpg v 18mpg is nothing, but it's not any worse, that's for sure.
I run only Euro oils in my Sequoia. Cannot tell anything about mpg, as it is horrid as always. But, timing chain assembly is definitely quieter.
 
Just my thought Toyota isn’t giving specific or unspecific permission to use a heavier weight of oil, but they are “telling“ you a fact that thicker oil in certain use examples may have more protection the owner of the vehicle ultimately makes the call the EPA tries to use dealers as an authority when they are just service provider and sales. EPA is the authority, but they have no authority to enforce on the consumer.
 
Just my thought Toyota isn’t giving specific or unspecific permission to use a heavier weight of oil, but they are “telling“ you a fact that thicker oil in certain use examples may have more protection the owner of the vehicle ultimately makes the call the EPA tries to use dealers as an authority when they are just service provider and sales. EPA is the authority, but they have no authority to enforce on the consumer.
I’m not sure they can enforce it on a dealer either. The rules state that the manufacturer must make sure that the tested grade is commercially available, and that the manufacturer vigorously dissuade the use of any other grade, but I’ve never seen language that they are required to use that grade for subsequent service fills.
 
I wonder what the "tight clearance" crowd thinks about this?
A friend of mine lost a Triton V-10 after using the wrong oil. The next few months will be interesting if manufacturers are forced to modify their "specifications" because they have no other option. If the shortage is real and long-term, this year may settle the viscosity debate once and for all. Time will tell, but my popcorn popper is ready. ;)
 
A friend of mine lost a Triton V-10 after using the wrong oil. The next few months will be interesting if manufacturers are forced to modify their "specifications" because they have no other option. If the shortage is real and long-term, this year may settle the viscosity debate once and for all. Time will tell, but my popcorn popper is ready. ;)

If anything helped settle the viscosity debate, it's GM telling 6.2L truck owners to stop using 0W-20 and use 0W-40 instead.
 
That was a short lived recommendation though
GM's direction to run the 0W-40 still applies to the engines not deemed to be replaced under warranty but still to be used with the thicker oil. Source - LINK

But GM's move on that reinforces the fact that engines can use thicker oil than what's called out (recommended) in the OM, which is the focus of this thread.
 
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