The case of the disappearing oil

Dear Car Talk:

Where is my oil? Our 2013 Equinox with 52,000 miles has disappearing oil. Between the last three scheduled oil changes, we lost more than 2 quarts. Last week I checked the dipstick, and nothing registered. I added a quart, and it came up to 3/16 of an inch on the stick. Now the oil-change readout says 29 percent left until oil change. I took it to the dealer, and they found nothing — nada. They saw no drips, no signs of oil running down the outside of the engine, and when the car is running, they saw no smoke coming out of the tailpipe, and no smells. They are stumped, and so is this chump. So, what are your thoughts?

– Charles

Well, unless some neighbor is sneaking into your driveway at night and siphoning out your oil, you’re burning it, Charles. It just might not be enough to be visible yet.

If you lost about 2 1/2 quarts between each of your last three oil changes, that’s not a good sign on a car with only 52,000 miles. But it’s not “start fracking in the backyard”level oil burning yet, either.

If you’re a typical driver, you change your oil every 7,500 miles or so (just over 12,000 Kms). Maybe more. So you’re burning the equivalent of a quart every 3,000 miles.

Normally, people start complaining to us when they’re burning a quart every 1,000 miles, or a quart every 500. My brother wouldn’t even buy a car unless it was burning at least a quart every 250.

My more immediate concern for you is that you allowed the oil level to get more than a quart low before adding oil. So you need to be more vigilant, and check it more often. Letting the engine run low on oil will only harm the rings and increase your oil burning.

Unfortunately, oil burning also tends to get worse over time. So your current rate doesn’t bode well for this car’s longevity without an engine rebuild at some point. So if you’re still under some sort of extended warranty, you want to be sure to have your dealer document the oil loss — even if they claim to be stumped by what’s causing it.

They do that by sealing the system, so you can’t tamper with it, and then having you come back in at certain intervals to document the oil loss. That may give you a better case to make, should the oil consumption take a sudden turn for the voluminous in the near future.

Alternatively — and this probably would be my approach — since the dealer didn’t see any blue smoke coming out of the tailpipe when you took the car in for service, you can assume they won’t see any if you go back next week to trade in the car, Charles. Good luck.

Changing your oil regularly is the cheapest insurance you can buy for your car, but how often should you change it? Find out by ordering Car Talk’s pamphlet “Ten Ways You May Be Ruining Your Car Without Even Knowing It!” Send $4.75 (money order in American funds) to Car Talk/ruin, 628 Virginia Drive, Orlando, Florida 32803.

Car Talk shares secrets on how you can save tens of thousands of dollars on your cars over the next 20 years in the pamphlet “Should I Buy, Lease, or Steal My Next Car?” Send $4.75 (money order in American funds) to Car Talk/next Car, 628 Virginia Drive, Orlando, Florida 32803.

Order Car Talk’s pamphlet “How to Buy a Great Used Car: Secrets Only Your Mechanic Knows.” Send $4.75 (money order in American funds) to Car Talk/used Car, 628 Virginia Drive, Orlando, Florida 32803.