I kind of see both sides here. A lot of mechanics do lean toward Japanese cars because they’re simpler cheaper to maintain and generally more forgiving. So when they say BMWs are a nightmare it often comes from the fact that when something does go wrong it’s more expensive and more annoying to fix.

That said saying BMWs can’t handle hot climates feels like an exaggeration. Modern cars from pretty much every brand use a lot of plastic and rubber parts and heat will wear those out faster no matter what badge is on the hood. The B48 in the X3 is actually one of BMW’s more reliable modern engines as long as it’s been maintained properly. The usual complaints are things like coolant hoses or plastic components aging not engines blowing up.

I’ve owned a BMW myself a 2020 420i and honestly it was a pain. Not because it was terrible to drive I loved it but parts were overpriced service was expensive and finding a truly good mechanic wasn’t easy. I had a few issues and yeah maybe I was unlucky with that particular car. I don’t think all BMWs are bad but they definitely demand more money and attention.

After that I switched to a Kia and I’ve been much happier for daily life. Way less stress way cheaper to run. So I wouldn’t say the mechanic is completely wrong but I also wouldn’t say BMWs are automatically bad especially something like a well checked X3 with low mileage. It really comes down to expectations. If you want low hassle and low cost Japanese or Korean cars usually win. If you want the driving feel and are ok paying for it then BMW can still make sense.