js2>'eating' engine oil is quite dependent on the engine, irregardless whether it has a turbo or not. from what i've heard s2000 and rx8's 'eat' a lot of oil, and they're not turbos and evos dont 'eat' oils. of course, these might be one off cases so you should check the oil once every few weeks.
the s15r MIGHT 'eat' some oil, cos the one s15r i've experienced seems to be running low when its due an oil change. not to dangerous levels though, about 3 quarters of the way between the suggested empty and full range.
go ahead with the s15r, for the money these cars are going for now, not a lot of cars comes close with the performance and looks. keep us posted on the buying process and experiences you have yea?