Exploring the Performance of Diesel Vehicles: A 1,500 km Test in Romania

There’s a joke I make every time I go back to Romania, which is that I didn’t need to leave to find horror stories. I just needed to drive between Brasov and Bucharest at the wrong hour. The problem is a mountain pass that’s been down to one lane in each direction for longer than I care to think about, with no real alternative route around it. BMW Romania handed me a 2026 X3 40d xDrive in Tanzanite Blue over an Amber and Atlas Grey interior, and I used it to prove the joke right: nearly 1,500 km through Deva, Hunedoara, deep into Transylvania, up to Brasov, out to Viscri, and down into Bucharest, with my wife, our two kids, two car seats, and enough luggage to make Vlad the Impaler reconsider his hospitality standards.

The X3 40d isn’t sold in America and never will be. That’s exactly why I wanted it. The B57 3.0-liter inline-six diesel, now with 48-volt mild-hybrid assistance, makes 303 hp and 670 Nm (495 lb-ft) of torque, does 0-100 km/h in 5.4 seconds, and carries a combined WLTP claim of 6.6 liters per 100 km, somewhere around 38 to 42 mpg depending on which side of the Atlantic is doing the converting. Diesel is still the default choice in Romania for anyone who actually covers ground, and after a week with this car, I understand why better than I did before I left.

A Trip To The Village King Charles Likes To Visit

Viscri is the kind of place that makes you understand why a British monarch would quietly buy a house there. Narrow lanes, fortified Saxon church, storks nesting on chimneys, and none of it built with a 4.7-meter SUV in mind. I threaded the X3 down streets that felt sized for a horse cart, which, this being Transylvania, is not always a hypothetical alternative form of transport. And it’s quite charming, if you ask me.

Getting there and back was the easy part. The trouble started on the road everyone in this story eventually has to take: Brasov to Bucharest, roughly 170 km, which Google Maps insists is a two-hour drive and which reality insists is a personal test of character. One lane each direction through the mountains, no real detour, and on a bad day it’s six or seven hours of watching the same three trucks inch forward ahead of you. I’ve done this drive in cars that made me hate my life by hour three. The X3 didn’t. The seats held up, the cabin stayed quiet, and by the time we rolled into Bucharest I was tired from being a parent, not from being punished by a chassis.

Six Cylinders, One National Pastime

Overtaking in Romania isn’t really optional, it’s closer to a civic duty. Every stretch of two-lane road eventually puts you behind a tractor, a truck hauling something you’d rather not think too hard about, or a fellow driver who has decided 70 km/h is a personal ceiling. The B57 turns all of that into a non-event. The torque is there from just off idle and doesn’t let go, so the gap that would require a running start and a prayer in a four-cylinder car takes half the commitment here. I stopped counting overtakes by day two, mostly because the car stopped making them feel like events worth counting.

It’s smooth doing it, too. Idle clatter is nearly gone, and under load the engine sounds like it’s working, not complaining. The ZF eight-speed shifts fast when asked and disappears when it isn’t, and the two got along well enough that by day three I’d stopped thinking about the drivetrain at all, which for a car doing this much driving is close to the highest compliment I can give it.

The steering is lighter than BMW enthusiasts are conditioned to expect, and I liked it anyway. Nobody wants heavy, artificial resistance while three-point-turning out of a Bucharest parking spot with inches on either mirror. The seats earned their keep too, real bolster and thigh support, and across multiple full days in the car my back never filed a complaint, which is not something I can say about every press loan I’ve driven.

Ambient Lighting: Great For Kids, Less Great For Door Panels

My kids treated the ambient light bar running across the doors and dashboard like their own personal disco, cycling colors on command whenever the traffic jam threatened to get to them. You can switch it off if it’s not your thing, and there were moments I wanted to, but as a distraction device for two small children stuck in a car for the better part of a day, it did its job better than anything I packed for them.

What didn’t impress me is something I’ve said about BMW cabins before and will keep saying until it changes: the plastic on the doors isn’t good enough for what this car costs once you option it the way most Romanian buyers do. The new interior door handle in particular feels flimsier than the rest of the car around it.