Also hybrid doesn't lend itself to diesel as well.
One of the benefits of hybrids is the relatively poor low end torque of a gasoline ICE. The electric part of a hybrid dovetails nicely with this deficiency. A diesel's low end torque is where it shines :!:
And diesel being more fuel efficient to begin with will exhibit less MPG benefit with being hybridized.
Diesel having a _much_ higher compression ratio than a gasoline ICE the hybrid part would have to be correspondingly larger for the required extra "grunt". So unless you go with the "Toyota" type of hybrid there is this third drawback to the marriage.
Finally the cost effectiveness / pay back time will be _much_ longer with a diesel.
But from an emissions perspective of course anything that reduces ICE on time is a benefit as long as the pollutants emitted in the creation, maintenance and disposal of the added technology don't exceed this obvious front line savings.
HTH!
