When the Liberty was available with a Diesel it had lots of torque and slightly better fuel economy. In the end it wasn't a big seller and even my local dealership said it wasn't worth the extra money.Fair enough. The government mandates a lot of emissions and safety equipment, but overall configuration is still a pretty free market determined by supply and demand.
The government doesn't mandate configuration. Yet. I don't believe there are any government rules that would specifically forbid putting a diesel engine in a light pickup truck (assuming the engine passes emissions laws, and we know such an engine exists).
So then you ask yourself, why is nobody doing it? Is it because every automotive manufacturer - VW, BMW, Mercedes, Chrysler, Ford, GM, Nissan, Toyota, Honda - they ALL don't realize there's this huge untapped market?
-Ryan
I saw an interesting study (around 2004) where Cummins brought over a medium duty Diesel truck engine from Europe (a 4L V6) to see how it would do with EPA emissions testing. Euro testing and American testing are different so it's hard to compare the two. The goal was to determine how much effort was required to meet US emissions standards if used in an SUV. The stock engine emissions was 2-3x the allowed limits for a start. Then they tried tuning mods to bring the engine into compliance. Their conclusion was that a completely new intake/fuel/exhaust design was needed.
Countries that import their oil prize fuel economy and even the gassers do way better than ours. Countries with oil prize clean air and set much stricter emissions standards.