Hmmm,

Not "completely" true. I drive Mercedes Diesels and they are not noisy nor smelly and have very good power. My full sized diesel powered S class sedan is much more powerful on the highway than my 240. The difference between gasoline and Diesel engines are like the differences between piston and turbine based aircraft engines. While the piston engines develop power quicker than the turbine based engines the turbine based engines are much more powerful. The diesel engines get most of their power from torque. Granted the Volvo and VW engines are on a totally different quality level than Mercedes engines the common urban legends about smokey noisy diesels are generated from poorly maintained cars with severe engine problems. Even gas engines stink and make noise when they are at the end of their service life. A high torque engine can be fun too. I have had lots of fun passing high end sports cars on a steep grade without even downshifting while their engines are screaming through every gear change as I effortlessly glide by them.

Personally if I were going to put a diesel into a Volvo I would consider doing an OM-617 Mercedes Benz 5cyl turbodiesel in there. The problem your going to run into is emissions. Even though you have an emissions exempt engine in your car your VIN number will still register as a gas engine. Depending on your emissions laws there may be some sticky paperwork to go through to get your "Gas VIN" exempt from emissions.

Before you do your conversion go find a diesel powered car and drive it for a week or so. Some people (especially the lead foots) can't adjust to the different way the power band works in these cars. For high speed highway cruising they are ideal. My Full size car (with over 380K miles) gets 30mpg cruising comfortably at 80mph on the interestate. If your looking for longevity and fuel economy diesel is the way to go.