The story goes that when UPS decided on the 757's, Boeing made it a condition of the deal that when the DC-8's were to be retired from their fleet that they would be turned over to Boeing to be scrapped.
Would be ashame to scrap them. Just as an example, comparing the DC-8-62F with the B757F (not to mention the -73F which is larger/heavier but with a reduction of 30% in fuel burn compared to the -62F).
The B757F has high payload-range restrictions compared to the DC-8-62F (and -63/-73F). The B757F carries just over 35 tons for approximately 4 flight hours whereas the DC-8-62F carries 42 tons for over 7.5 flight hours. Additionally, the higher lease rates of the B757 make its overall operating costs more expensive than the DC-8's.
I read in a report some time ago that for the B757 to equate the total operating cost of the -62F, the fuel price would have to increase to $2.50 per USG. Perhaps the "8" may still have a future when biofuels catch on?
Instead of scrapping the "8" -60/-70 series, Boeing should put at least one of each in the Museum of Flight and preserve them well.
Green-dot