Edmunds.com reviewed payback times for hybrid-electric and diesel-engine vehicles

Average premium for all hybrids is $4,981

Premiums ranging from Toyota Camry Hybrid at $289 to Lexus LS 600h L at $15,969

Average diesel-engine premium, meanwhile, currently is just $2,360

Gas and diesel fuel prices staying low, and uncharacteristically consistent, during summer

Latest round goes to diesel

Two factors currently working in diesel's favor:

Diesel-fuel prices have dropped and price "premium" for diesel technologies is low

As gasoline prices stay low, hybrids struggle to justify typically higher initial-cost premium

Lower cost premiums / availability of tax rebates, diesels much better payback proposition