There are a hell of a lot more gasoline-powered Toyotas out there than diesel VWs. At least in the U.S., diesels are generally dirtier. That might be because

There are a hell of a lot more gasoline-powered Toyotas out there than diesel VWs. At least in the U.S., diesels are generally dirtier. That might be because our diesel has mostly been high-sulphur, not the cleaner diesel that Europe has. Most diesel engines are built for heavy equipment, tractor-trailers, or pickup trucks in the U.S.