2010 BMW X5 diesel vs 2010 Benz ML350 diesel

[IDoSeaDoo]

Here we go guys, time to tell me why I should get the diesel X5 versus the Mercedes ML350 Bluetec. I understand both use the def fluid, which in my book is a big plus. Despite my obsession with boats, I am an environmentally conscious person. But what are the benefits of the BMW over the Benz? It appears the X5 has more power, yet can tow less and gets worse fuel economy. While I prefer the looks and styling of the X5, the Benz is not far behind. I am asking you seasoned owners why you made your choice, and why you love the X5 and over the Benz.

[IDoSeaDoo]

I stumbled on some information regarding the Benz bluetec diesels that suggests that they are ticking timebombs. Seems like they are designed to run REALLY REALLY hot to meet emissions. The oil they prescribe these engines cannot tolerate the heat, and turns to sludge, starving critical engine parts of lubrication. It's a $24k repair bill from the dealer, and about $6000 for a reman engine from a reputable shop. Has anyone heard of any such horror stories about the BMW diesels?

[jclausen]

All I know is these systems to make the diesel work are very complicated and expensive to repair. I would never by one because I don't see the benefit of owning it. The fuel is not cheaper

[IDoSeaDoo]

All I know is these systems to make the diesel work are very complicated and expensive to repair. I would never by one because I don't see the benefit of owning it. The fuel is not cheaper

Do you not have to use premium fuel in the gasoline X5? The diesel here in Florida is only 10% more expensive than regular, but you get 30% better economy, so there is a little gain there. But with diesel, you also can tow more, as there is more torque. I believe the transmissions are built sturdier as a result (correct me if I'm wrong on this one). Also, with the new exhaust/emissions technology, today's diesels emit less pollutants per mile than their gasoline counterparts. Again, that's my speculation.

[IDoSeaDoo]

Well, I have decided 100% against the Bluetec mercedes design. My decision stems from the fact that you can not (easily) remedy the problem of the turbo cooking the oil in the manner I want to. The remedy I speak of involves installing a dedicated oil system for the turbo charger. I found some high quality components made for the racing world that would accomplish this. It would require a small sump tank, a high-temp oil pump, oil cooler, some oil lines and two pressure switches (for redundancy, they're cheap). The system would use a more heat tolerant oil than what is prescribed for the engine (safe for the DPF). A synthetic ester based oil, like a good motorcycle oil. The system would keep the turbo cooler and supply the bearing with consistent and high quality oil. It would help the turbo last longer, as well as greatly reduce the amount of sludge and coking in the engine.

The reason this is very hard to do on the Mercedes Bluetec is because of the way the turbo is bolted to the engine. The oil return does not have a dedicated line like on most setups. Instead, the oil drain hole mates with a hole on top of the engine as you bolt it on. Separating it from the engine oil supply would require to rework that whole installation system. I'm still researching the X5's M57S turbo system, but from I've found, I believe it's just one turbo that has the traditional oil feed and drain lines that bolt to the turbo. These could be easy to block off on the engine and attach my custom oil system. I believe this would be a big help to extending the life of these engines, and making diesel great again. They are definitely not as robust and long-lasting as they once were.