Mercedes-Benz GLS 450d long-term report: A diesel, is a diesel, is a diesel!

Electrification is keeping the combustion engines we love alive and well. Case in point the big 3-litre six-cylinder diesel, on this even bigger, Mercedes-Benz GLS 450d SUV. Now I’ve been spending an inordinate amount of time in electric cars and by all logic should have got accustomed to the silence and refinement; the lack of vibes or anything really emanating under the bonnet. Except that faint murmur of the diesel rumbling away in the distance, far from an intrusion, it’s honestly a joy. It’s the beating, thrumming, heart of the car. It makes the car feel alive, and not an appliance taking you to work and back. All this without the traditional coughing, sputtering and belching associated with diesels, especially on crank-up.

Here's where electrification comes in handy. The OM656 six-cylinder diesel in the Mercedes-Benz GLS 450d gets 48-volt mild-hybrid technology which powers the integrated starter-generator. Operating faster and quieter than the traditional starter motor, the ISG uses controlled electrical torque to spin the engine gently and precisely, no need for a ramp-up which reduces vibration and sound during start-up. Also since there are no gears meshing, there is no mechanical cranking sound, which you get in a traditional starter where the pinion gear engages the flywheel producing the whirring sound. The resultant smoothness of this diesel engine is remarkable and the benefits are particularly noticeable in stop-go traffic when auto stop-start is active. With the ISG engaging the flywheel instantly and turning the crankshaft to start the engine, there is no delay, no shudder, no chug-chug-chug – all of the (intrusive and irritating) reasons we used to switch off start-stop in traffic.

And of course, the system recovers energy usually lost under braking and deploys that to torque-fill so you get very good throttle response, no gaps in the torque curve, and even a boost of torque when you need it. The 750Nm of torque makes the GLS an absolute mega mile-muncher and with an average fuel consumption of 8kmpl plus the 90-litre fuel tank, it delivers a 700 plus kilometre range. Not to forget that behind the steering wheel the GLS gives you that king of the road feel. I love driving it. Except I’ve been doing it all wrong. I completely skipped the main event. The back seat!

That got addressed on a recent trip to Stuttgart to drive all the generations of the Mercedes-Benz S-Class. I was flying out of Mumbai but flying back to Pune (via Delhi) and so couldn’t leave the car at the airport; Mercedes-Benz very kindly provided me a chauffeur to bring the GLS back to Pune and I took the opportunity to experience the back seat. First impressions – acres of space. The seats are super comfortable and so large that you can even sit cross legged. There’s adjustable recline angle, pillows on the headrest, and there are sunroof controls at the back. The wireless charger in the armrest can fast-charge a compatible phone.

Most importantly though, the ride quality is so good I could hammer out this report in the car itself. Many of you have pointed out we don't do full justice to our long-term test cars and only focus on the driving experience. I see your point. And I can confirm, 3 hours in the back seat of the GLS, on the laptop or the phone, and I reached the airport without a headache. Three days later, back home, and the GLS’ fuel gauge was still above half a tank (it was a little below full when we left for Mumbai). Like I said, a diesel, is a diesel, is a diesel.