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[Solved] Should we question the reliability of Japanese I4 and V6 engines?

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It seems that all modern engines in more recent years (2016-present) manufactured by Toyota, Subaru, Mazda and Honda all feel like they are the same in some way IMO.

The ones that I am talking about are:

  1. 4 cylinder engines for regular vehicles (cars and SUVs)
  2. 6 cylinder engines for luxury vehicles and ones who want more power in their cars and SUVs

If all these engines feel like they are the same, should we question the reliability of them? Should we even question the reliability of the previous 4 and 6 cylinder engines? I feel like the predecessors have some similarities as well.

5 Answers
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Of those four companies, they all have relatively different renditions of the 4 and 6 cylinder engines. 

Subaru easily sticks out because they are boxer engines for 4 or 6 cylinders. Toyota, Mazda, and Honda have inline engines for their 4 cylinders. And V engines for their 6 cylinders. (Although Toyota use to make an inline 6, and Mazda is planning to come out with their first inline 6.)

Honda sticks out in their V6, because they still use timing belts. Toyota and Mazda all use timing chains. 

This is just the tip of the iceberg. There are so many differences between their engines. Although most of them are reliable, it is hard to say they are the same. Because there are more nuances that make them differ from each other. 

 

6

Come again?

 

What part of my question do you not understand? Just curious.

all of it

Here is my question: Should we question the reliability of Japanese I4 and V6 engines?

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all modern engines in more recent years (...) by Toyota, Subaru, Mazda and Honda all feel like they are the same (...)

In what way? they couldn't have been more different.

It's how Subaru's FB20 Boxer couldn't have been any more distant to the Honda EarthDreams 1.5T...

Even the fairly similar engines like Mazda's SkyActive-G 2.0 is extremely dissimilar to the Toyota DynamicForce M20A.

If all these engines feel like they are the same

Engineering wise they're different, they drive differently, and they have different concerns.

should we question the reliability of them? Should we even question the reliability of the previous 4 and 6 cylinder engines?

YES. Most of them have serious flaws, like oil consumption on Mazda turbocharged units, or how on Toyota's DynamicForce the EGR cooler cracks and causes it to burn anti-freeze in addition to some manufacturing defects, or how Mazda's sky active non-turbos had an issue with the accessory belt bursting, or how Subaru's 4cyl boxers engines still have a tendency to overheat and burn oil although they get damaged very easily by those things, or how Honda still has no clue why their 1.5T randomly misfire, and A LOT of other concerns...

Can you share a little more about what you know about the Toyota cracked EGR cooler? Is it still a problem? Have they fixed it?

If they'd just fix it, it wouldn't be Toyota - they blame it on the owners.
But it's far from this engine's only concern. https://static.nhtsa.gov/odi/tsbs/2021/MC-10206528-9999.pdf
Anyhow, it's a good engine - just some possible faults to watch out for.

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Posted by: @kp

Should we question the reliability of Japanese I4 and V6 engines?

Why?

Do they all have some hidden catastrophic flaw, lurking in their bowels?

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Here is my question: Should we question the reliability of Japanese I4 and V6 engines?

We should question the reliability and longevity of any new design, Japanese or not.  That being said, I would still take a chance on a Toyota I4 or V6 over a Honda I4 or V6 over a Mazda I4 over a Subaru Boxer H4.

What I like about Toyota, they have more naturally aspirated designs than the other Japanese companies, incorporate both direct and port injection (to mitigate carbon buildup on back of intake valves), use timing chains, the valves for all practical purposes do not need to be adjusted like they need to on Hondas, and they don’t incorporate cylinder deactivation at all (like they do on Honda V6 engines and some Mazda I4s).

That being said, I am also a proponent of waiting a few years on new designs to see how they shape up.  I am not about to cut any automaker slack, Toyota included.  In fact, I believe Toyota is past peak reliability and has been for a while.

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