Mileage/Maintenance Question

If the maintenance guide for your vehicle says to change the timing belt at 90,000 miles or 72 months, but you only have 30,000 miles on your otherwise very well maintained vehicle after 6 years, is it really necessary for the timing belt to be changed?

Of course not. You can wait a few more months for the belt to break and then simply replace the engine or the whole car.
Or… You could take the cheap way out and replace the belt now, since it is due.

Yes, it should be chenged. Elastomerics dry up, crack, and become weakened even if they’re not used.


Is your advice the same for non-interference engines as it is for interference engines?

If so, I’m not sure that your advice is based on technical knowledge.

On the other hand, tsmountainbike makes a good point. A belt might wear out due to age - regardless of mileage.

And he doesn’t suggest a doomsday scenario based on an unknown (regarding whether the enginge is interference/non-interference)

Thanks, tsm.

Even if it is non-interference, the chance of damage remains. It could be damaged by the truck that rear-ends you when you lose power. It could be damaged during towing, and so on. If you try to be a cheapskate, then you will just wind up paying more. I stand by my statement. The cheapest thing is to replace it before it breaks. They give the interval as mileage OR time for a reason. Why do so many just assume they can ignore the time part?

Also, since you didn’t give the make/model/year of your car, I am free to assume that it is an interference engine.

You really should replace it now, even if it is not an interference engine.  After all it is not too healthy to have your engine stop without warning on a crowded freeway. 

As noted there are good reasons they list both time and miles.

Knowing something about the vehicle you’re talking about would help a lot.

If I were sure it was a non-interference engine I might wait a while longer, especially if the vehicle is garaged. Having said that, I had a timing belt break while I was driving. It was a non-interference engine, but the power steering stopped working, the power brakes stopped working, and the car immediately started losing speed.

To this day I’m thankful I was not in the passing lane on the freeway when it happened, or in a bad part of town, or in the middle of a downpour. If the timing belt breaks the engine stops running, and you’re stuck wherever you happen to be. I had to push my car a block down the street to find a place to leave it, then had to arrange towing the next day. Luckily, the car was not vandalized overnight.

Now, one of my cars has an interference engine, but doesn’t get too much mileage. The schedule says 90K miles or 72 months. I waited longer than 72 months to replace the timing belt, even though the mileage was only 60K. I think the car was about eight years old when I had the belt replaced.

I gambled. I was lucky. I’m not so sure I’ll do it again, though.

The mfg recommendation is based on tests results. The tests are not real world but accelerated wear test simulations. Based on the results the mfg recommendations should result in no failures unless the belt was defective in the first place. If your belt has lasted this long it did not have a defect. I worked for a company that made auto timing chains and we had test motors running all the time to see how the timing chains held up.

After 72 months the chance that the belt will fail increase. Exactly what that risk is remains unknown. If you are comfortable dealing with the unknow then don’t change the belt. Interference engine or not only affects the amount of damage and costs to get the motor going again if a timing belt fails. If tight money is the reason behind not changing a timing belt, then tight money will be the reason behind junking the car rather than fixing it if indeed it is an interference motor.