Not sure, i'm not very technical minded. I was just reading through some stats for US trucks, and noticed the big 5.0 Litre engine one's can only tow about 7000 lbs, which is what a 2.5 diesel can tow usually.
I agree that more small diesels would be wonderful. The American manufacturers (and VW) just lost a sale – – I bought a Mercedes GLK 250 Bluetec just to get the 2.1 L diesel engine, along with AWD and enough ground clearance to be able to handle a dirt road or drive into a pasture when needed. (Mobile medical practice, we get called out to strange locations fairly often)
With as many miles as we drive I appreciate the 34-ish mile per gallon in this vehicle.
Our other vehicle is a VW Passat 2.0 L TDI. We often get 47 mile per gallon in that. We specifically told the product development manager for Volkswagen that we wanted VW/Audi to bring out an A3 or Tiguan-sized vehicle with a 2 L engine. We need mileage, torque, and all-wheel-drive. They blew it
On a side note we drove and loved the Ram 1500 Eco-diesel. However 28 miles per gallon does not quite do it for us. We have no requirement to tow 9000 pounds. The Jeep Grand Cherokee eco-diesel lost out due to poor visibility out of the drivers seat and higher noise level inside.
Whatever they're doing to diesels to make them pass emissions in the US seems to be working. I think once they find a way of reducing N0X quickly and cheaply, they will be able to start considering smaller, cheaper diesels for the US market. As trollbait has pointed out numerous times, fuel is so cheap in the US anyway, there is no market for a diesel, and the one's that are available only offer small benefits in terms of economy. I've always thought the US has used N0X emissions as an excuse for far too long, even a small diesel like mine with C02 emissions that match a Prius, has N0X emissions so low, the C02 output is 70000% higher.
The VW 1.6 TDI Bluemotion is possibly the best engine for economy, it's been tweaked and tuned by VW's eco technicians. Recently, a hypermiler managed an impressive 97 MPG on a 1000 mile trip in Europe.
My friend has an Isuzu pickup 2.5 TDI and he gets close to 40 MPG in it, and can still pull over 7000 lbs. American trucks seem to have massive yet underpowered petrol engines, bit of a joke compared to the stuff on sale in Europe.
I don't know.
I have a F-350 it pulls 33,000 lbs. 7000 lbs is a bit of a joke compared to the stuff we pull around here.
Diesel engines cost more to build. The compression ratio is much higher than gasoline engines, so physical loadings on crankshafts, rods, engine block and other components are substantially higher so they have to be built more robustly. This costs money.
Historically, Diesel fuel cost a lot less than gasoline because it wasn't in high demand, but is a byproduct of refining operations. This is no longer true. China has no refining capacity of their own, nor do they have an electrical infrastructure that supports their rapid industrial expansion. The plants have on-site large Caterpillar generator sets. These power plants burn Diesel fuel that is imported from countries with refining capacity such as the United States. So Diesel now costs more per gallon than gasoline.
Another detriment to Diesel ownership is getting it started in the morning in sub-freezing weather unless you leave it "plugged in". GM sold a lot of 8.1L gas engines in its HD pick ups to people in the North East that needed the towing power of a diesel, but didn't want to deal with the cold-starting hassles, or pay the ~$7,500 additional for the Duramax.
Emissions systems for diesel engines are more complex, and cost more. Up until the past few years, Diesels were exempt from periodic emissions testing required for vehicle registration. This is no longer true, Diesels are now tested. So this "advantage" no longer exists.
One of the biggest "mysteries" in the US domestic truck market is why hasn't GM ever put the Duramax in the Suburban / Yukon XL? Technically, the two platforms are identical, so the hardware is available. The reason I've been told numerous times is "no demand". They could easially build a Duramax Suburban, but not enough people will buy it, so they don't.
So it's the cost of several factors that narrow the advantages of Diesel over gasoline to the point that the extra costs of fuel and acquisition don't justify the higher MPG potential. Which makes demand for small diesel engines in the US market low, so manufacturers aren't inclined to develop and then produce them.
You can't buy what isn't built. And they won't build what won't be bought by enough of the market to make it profitable. Regardless of how much "sense" it makes.
I have a diesel Silverado 4x4 and a gas Silverado 4x4. The gasser is much cheaper to maintain and a better drive around vehicle. If you need a pickup to move couches, garbage and stuff a gasser is much cheaper to buy and maintain. I use the diesel to tow very heavy loads, like a travel trailer, a diesel outperforms a gas engine by a lot in MPG and low rpm torque when towing a heavy load. When towing long distances over steep grades, I just put the diesel in cruise control and it just maintains, the gasser will have to be almost floored to do the same.
Pick up trucks with small engines are not very useful, had a F100 with a 300 CI 6 in it, the truck was no good for hauling anything, it was too slow and underpowered for a full size truck. Generally trucks should have a decent sized engine to perform their primary job, otherwise get an economical hatchback to putt around in. Trucks are not passenger cars.
Mercedes is offering their full size vans that can be upfitted for heavy duty use, and still their 2.1 ltr diesel 4cyl, so a small diesel in a large vehicle can work. In their current ML250 and it's replacement the GLE, they use the 2.1 ltr diesel too. Not exactly light vehicles.