The only thing ULSD will harn under your hood is old seals in an IP, it will not damage internals at all. Some cars will have IP seals start leaking while others will not. So far my 91 is hold up fine, but only about 1/2 tank of ULSD has been bought by me, not sure about PO fuel.
Only ones I have seen have trouble were folks switching from BD to ULSD no-bio, but there has been so much confusion due to rumors and people not reporting complete facts.
I know the MB & CRD both seem to run a lot quiter and with less smoke then on LSD thats is for sure. Some have reported hard starting on cool to cold days, the CRD has this problem but not the MB for some reason.
