my $87 a month is for the same coverage as yours, we call it liability here. I do have some dollar amount limits increased, but it only adds like $6 or so to do that.
diesels in general get better gas mileage than gas engines of similar size and power. we used to have options back in the 80's, had diesel vw's, mercedes, and audi's that were 50ish mpg. the most fuel efficient american car ever built was a Chevette that had an isuzu diesel in it and would almost get 60 mpg highway. of course your talking 60-100hp diesels and the only thing they try to sell to us is big truck hauling turbo diesels. theres also the biodiesel and veg conversions to add to that cost savings, so I for one, am disappointed that we don't have more options in diesels.
VW has been better than most at giving the american market some diesel cars. my sister in law has a Jetta TDI that gets 50ish mpg. problem is that so many of us don't remember that they already had a 50mpg Jetta 30 years ago. I do think the TDI's can actually do better than that, theres a whole club of owners who talk about the 1k mile club or something like that (1k miles on 1 tank of fuel).
the biggest problem today is that those cars are either old 300k mile cars, or brand new $40k cars, with little in between. I owned 3 Chevettes when I was a teenager, but the average american wouldn't or couldn't spend the time to fix and run one. It also takes a lot of money to buy a fuel efficient new car so the great majority of us who have to keep an eye on the bottom line cant afford to drive cheap. what is needed is a $3k-$5k option, where someone may recoupe fuel costs vs car and insurance payments in a year or so. I think you would see a large jump to alternative fuels at that point (not that I would classify diesel as "alternative").
I dont know what the resistance is to be honest, other than someone just not wanting to do what everyone else does. I'm not a fan of hybrids, though they are our best common option currently. even they only really get 40ish on the average and that can almost be done on a gas engine if its built for that. diesels are one of the most flexible and dependable systems around, get great mileage, and have already been able to work out most bugs and problems. All they need is a shipping invoice and an add campaign, were plenty malleable in this country.