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Timing belt replacement based on age and not miles for low mileage cars?

I know of someone with a 2002 Mazda Millennia with only 50k on it. The timing belt calls for changing every 100k but I was wondering if age is as much of a factor as mileage. I see no reference to this anywhere but know it applies to tires so why not belts?

Also, I am somewhat worried I may have purchased a Gates “New old stock” belt for another car. It is new in the box but may have been sitting around for a while.

Both these are non-interference engines but a failure would still be inconvenient. Are timing belts much of a concern with age or should one mainly be worried about mileage?

Good idea. Rubber (and fabric) ages with both. Not a “bad” idea to replace it sooner then later. Even though it may be non interference, you are right. It could still fail at the worse possible time and there is no substitute for confidence . I would definitely replace it some time in the near future.

Time wise the most I’ve seen for timing belts is 7 years, I myself have pushed one belt to it’s breaking point which happened at about 100k and a little over 10 years. I had already purchased the belt, WP and the rest of the installation stuff, it just happened to break a few days before I had planned on doing it. Replaced the belt and everything else right where it broke, inconvenient ? Yes. Impossible task, No. I would definitely NOT recommend this this maintainence schedule to any one in their right mind.

Most manufacturers recommend a 7 year interval max. The Mazda should definitely get a new belt.

I wouldn’t worry too much about the age of your other “NOS” belt. Rubber chemistry is so good these days that belts rarely fail due to age. Sitting on a shelf for a year or two isn’t going to hurt it. Put the belt on and change it in maybe 5-7 years, or sooner if the mileage warrants.

I believe many Toyotas have 9 year intervals. I would definitely replace it.

Gotcha. I figured this might be a concern. The Mazda in question has the 2.5L V6 and the other engine in question is a 1.0L 3 cylinder SOHC Geo Metro engine. I have demonstrated that these are non-interference firsthand by having a belt break. The DOHC versions of the Suzuki G series engines are interference so be careful if you have one of those.

I agree with @WheresRick‌

My 2005 Toyota has a 9 year timing belt limit, and that’s when I replaced mine.

Here’s something interesting . . . if that same engine is used in a slightly older Toyota, the limit is 6 years

I suspect Toyota realized that the timing belts were still looking good at 6 years, provided the mileage wasn’t sky high. As the others have said, timing belt composition has improved over the years.

On a side note . . . I once replaced a timing belt on a Camry which was 13 years old at the time, with the original belt. It had more cracks than a sidewalk, and it was clearly not long for this world.

I am not much of a Toyota person but aren’t most of these interference? That Camry sounds like it just dodged the bullet with the cracked up timing belt.

The engine I swapped into my Geo Metro was from a 1993 with only 70k. I like to pull the top 3-4 bolts from the timing cover and pull it back just a little so I can look at part of the timing belt. This was one extremely cracked up so I am guessing it is an original.

As for the change interval increasing with time, I have heard part of this has to do with improving chemistry of the rubber compounds. The newer belts are simply better even though the rest of the engine is the same.