2014 Toyota Highlander - When do I need plugs

Does a 2014 Highlander need new spark plugs at 120,000 miles

Probably . That will be in your owners manual in the maintenance section . Since you are asking there might be other things that need to done or should have been done.

Well, which engine??

One Toyota site is saying that the 3.5L V6, spark plugs are every 60K or 72 months
2.7L I4 is 120K or 144 months… That is which ever comes 1st for both engines…

So yes replace your spark plugs either way…

Always best to go by your owners manual as mentioned above…

Now if you just replaced them at 100K miles with the correct plugs, then no… But you gave us very little info to give you a proper answer with…

The 2014 Toyota Highlander maintenance guide shows spark plug replacement every 120,000 miles, this applies to all three available engines.

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No dispute, but replacing them more frequently, as long as done correctly, does no harm, except to your wallet. And more frequent plug replacement will likely do some good, e.g.

  • The plugs will be easier to remove, so less likely to cause cylinder head thread damage.

  • The plug’s average gap size will be closer to spec. Overly wide plug gaps can result in damage to the car’s ignition system .