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Oil cap is gone, engine seized

I have a question - we own a 2015 Mazda CX5 with 189,000 highway miles. Last oil change was done Oct 19th and it has since been driven 5000 miles or so. This week the engine seized up and wants 6k to repair it. Mazda dealer says there was no oil cap. Is there any way this happens other than the cap not being properly tightened in October or can an aging engine ‘shoot’ it right out?

If you had been checking your oil level once a week or at least every fuel stop you would have noticed the missing cap .


Thanks chief. I’m curious as to whether it’s feasible for an aging engine to have caused the cap being pushed off/pop off or not and whether the last oil change not being properly done is the only feasible explanation.

Oil caps rarely “blow” off." If it did, you’d hear it and it would likely have been caused by a hole in the piston. Leaving the cap off is the oil change place’s mistake. They may not have put enough oil IN the car at that time, it may have used some over the course of 5000 miles, and the engine seized up.

The oil cap being off should have set a check engine light. You driving the car 5000 miles and never checking the oil contributed to your engine failure. You own this, lock, stock and blown engine.

There are 3 reasons a cap can be missing. The locking feature can be defective and it can vibrate off in 5000 miles. Or it could have been improperly installed and vibrated off. Or it could have been left off at the oil change. There is absolutely no way to determine which one happened. The only solution to this problem is to do what I do. No matter how good the mechanic is, I always open the hood and look around at the repaired area. From hearing horror stories if I was to let someone else change my oil, I will never start my car without checking the oil first. If my vehicle loses no oil, I check the oil every 2000 miles. If I use any oil at all I check it at least once a week. Most will say 2000 miles is too long to wait between oil checks and they are right. That is my sin. Everytime I check the oil, I check all other fluids except for transmission fluid and look for any obvious problems. If my hood is opened for any reason the oil is checked. You may learn to have a routine similar to this, and it may cost you less hassles in the future.

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For a car this new, I’d consider a used engine from a junkyard. No need to pay for a remanufactured or factory new engine.

Most people drive a lot less than 47,000 miles in a year, so a junkyard engine probably has less than half the mileage yours does. It should be possible to have a low-mileage used engine installed–with a warranty–for less than $4k, probably closer to $3k.