The issue is our fuel quality, we are far behind European standards for Diesel (We just recently took sulfur out of the fuel, which by the way is going to cause serious issues for pre-sulfur removed diesels like lead-free gasoline did back in the day,) the fuel we have runs great in our American diesels because we crank them out to run on crap fuel. The diesel engines offered by many other manufacturers would actually have premature failure and issues unless the engine was modified to essentially use lower grade fuel
This is the second post in this thread to this effect, and it's just wrong. Or, to put it another way, you're painting with a very broad brush. Are there differences? Of course! But in the grand scheme of things, they're minor.
For 2007, the US got ultra-low sulfur diesel (ULSD) fuel. This was a huge step, and was the only roadblock to being able to sell modern, low-emissions diesel engines in the US. These engine use a diesel particulate filter (DPF) to mechanically filter out the soot. But they get clogged with sulfur unless ULSD is used. As of 2007, US and european diesel is more similar than different.
The biggest difference between the two is that euro diesel has a higher cetane number (analogous to octane). The "hotter" fuel in europe does have a performance advantage, but it's not that significant. And, more to the point, it won't keep a euro diesel engine from working well in the US except for a few (highly tuned) exceptions.
Just to give you a bit of background, I've been testing/developing euro diesel engines in the US since the late 90's. Not that it makes me an expert, but I'm not just a internet speculator. Or a guy, who knows a guy, who knows a guy.
And yes, some manufacturers have had some issues bringing their euro diesels to the US (VW tdi, for instance) but that is not as clear cut as some sources would make it seem. And the failure rate is shockingly low, but the flow of information on the internet may make you think otherwise. What you have to understand is that the function of diesel fuel in diesel engines is MUCH more complicated than gasoline in spark ignition engines. Small changes in chemistry and lubricity can have huge effects on performance and reliability. Factor in the "dosing" strategy, where fuel is added to the exhaust to initiate regeneration in the particulate filter and it gets way more complicated. But I'm trying not to get too off topic here, so I'll leave it at that.
I would love to see a diesel 4runner, but I'm a little skeptical that Toyota would do it without a big cost increase. The high compression ratio makes engine block design a real challenge and the fuel system and exhaust systems (including the particulate filter) are crazy expensive, too. To say nothing of all the precious metals that are needed in the catalyst. I'm not saying it won't happen, but I think a 6 or 8 cylinder would be cost prohibitive due to engine costs and the upgrades to the drivetrain that would be required. I'd ballpark it at $5,500 increase, depending on how many markets they could amortize the costs over. Personally, I think the value proposition of a 4runner gets very close to the edge of the cliff with an extra $5k tacked on. A 4 cylinder would be more feasible, but I think the US market would likely reject that. I would probably be the one guy in line with my checkbook , though.
