There needs to be a definite payback from the get-go. I think the mpg gap has closed, diesel fuel costs have leapfrogged from where they were in the 70s when it was cheaper than gas and gasser reliability has gone up due to fuel injection.

It's not so clear...

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)