My 2019 Mazda 3 only has 8,700 miles on it.
 

What does your owner's manual say? I am guessing that is says to change the oil at least once a year. I generally prefer to follow the recommendations of the people who designed and built the car. Many cars have a oil weight recommendation, such as 0W-20, that essentially requires a synthetic.

The 10K, 1yr recommendation started when that was required for the mfg to get energy credits. The car is designed to survive a 3-4 yr warranty period running that oil change interval.

If you want to keep a car +80K mi, due to tighter tollarances and smaller oil passages, the experienced mechanics recommend not to go more than 5K mi without an oil change. Especially with the higher MPG 2L turbo engines.

The reason for the 12 mo recommendation is that low miles and shorter drives increases oil contamination reducing lubrication effectiveness.

Especially for the newer high MPG turbo motors. The turbo gets very hot and the oil that remains in them continues to cook and degrade after the engine shuts down.

Don’t forget about variable valve timing passages and piston rings carbon buildup. If I have turbo engine I would be changing oil more frequently due to turbo and coking. But, that’s me.

IMO with new oils that a bit much unless the engine on it’s last legs and need to get every mile out of it. Twice year or minimum once year if not driven much IMO. My car changes around year mark cause or sets most of time in garage.

You didn’t mention mileage? Three times in 6 years only once every two years average. When it was newer get away with that, but if you plan on keeping it IMO every 2 years to long as engine ages it cokes up more when oil left in longer. Most people don’t keep vehicles pass 3 or 4 years so they never experience engine oil related problems. It’s the second owner that discovers oil related problems from lack of changes. That’s why most want see service records on used car.

Plenty of utube videos on oil change intervals. Most recommend 5K or one year which ever comes first. If you drive over road majority to time long steady speed trips can go longer cause that don’t have same effect on oil as stop and go short trip driving.

Talk about a reason to kick someone's @ss

They are changing the oil every two years and probably more than 6,000 miles. This is beyond what the manufacturer probably recommends. Yes, they should be changing it more frequently. Annually should be fine, instead of every two years, as it appears they aren't putting a lot of miles on the car.

Wow! lots of great opinions here. . .

I have always changed my synthetic oil every 5K miles, and never had a problem. Always other parts of the car failed before the engine failed. I have never had a major engine failure since I started owning cars in 1980, with regular oil maintenance. With a low mileage use vehicle, a change every 6 months should keep the engine working well, as well as a brake check as high humidity / rain can cause rust on the rotors and increase brake wear and stopping distances. . .

A quick tip about checking oil using a dip stick:
pull the dipstick with a cold engine in the morning after sitting all night. The oil will have drained down into the pan, and the cool/cold nature of the oil will give an easier read on the dip stick as the oil is thicker and easier to see.

Regular maintenance on a large cost item will keep the large cost item from becoming future junk later rather than sooner, as all vehicles are future junk.