Timing chain endurance miles vs. years?

It's as much a question of maintenance as mileage (use).

My 2006 has 220k and no indication of chain stretch. Dipstick had no varnish on it when purchased at 160k and I use 5k OCI. (Don't know exactly how "clean" it is inside because I haven't had to disassemble anything).

On the other hand I have seen late model cars with sludged up engines and measurable chain stretch at 80 or 90k.

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Apples and oranges. A timing chain can last decades without degrading.

You already know your wife's car is on borrowed time. That belt letting go is the only thing that needs to happen to make that car a worthless hulk, so think about it.

 

Also the timing chain design does have plastic guides - one for the chain tensioner, and a metal backed guide opposite that.



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Usually it was always a belt engine was not interference You can just run it down the road until the belt breaks pull it over to the side of the road pull off the covers drop on the belt let the tensioner go throw the plastic covers in the trunk and off you go same with my sienna 1mzfe belt breaks on the road no problem at all tow it home or change it on the side of the road if you like timing chains generally last the life of the engine what does that mean exactly who knows but generally what the manufacturer suggests is lifetime which you know is about a hundred thousand miles or so in my 20 r and 18 RC forklift engines the timing chains would last 20 years easily.

 

Usually they will break from age the plastic gets soaked with oil tears up the plastic and it snaps tabs break things like that If the chain stretches so much that it can dig into the plastic guide then obviously it's going to chew it up I usually that's where something's been run low on oil or gotten really hot or something weird's going on normally change stretch is a few thousands of an inch