the best bet is a 1.6l engine. I'll give you a list. mazda 3 1.6, mitsubishi lancer 1.6, also milleage is depend on how you dive it. like high reving before changing gears, not tunning up your engine etc,. never go up to 1.8L and 2.0L engine.
I would stick with a V6 and stay away from 4 cylinders. The life of the 4 cylinder cars are much shorter than those of V6 or V8 engines. V6 engines can still give you good gas mileage. V6 cars are larger which will help with passenger room and protecting you in the event of an accident. I have a 2006 Pontiac Grand Prix (no longer in production), but it gets 27 highway and 22 city driving. Not sure what is more important to you safety, room, and longivity; or mileage and cheaper payments in the short term.
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