Oh yes, the interiors can hold up well if taken care of. Mine had 207K on it when I bought it, and it looked as good as my son's car with about 70K on it. The prior owner was an insurance salesman in central Texas, so he drove a lot between the small towns. I had to battle the smoke smell in the 2010 GT I had also, but luckily bowls of vinegar and shampooing the interior helped a lot with that.
As for fuel, I've used mostly 89 octane in my 03 GT and it runs OK on it. But since gas is now much cheaper, I've been blending 1/2 and 1/2 - 89 and 93 octane for an average fuel price of $2.16. 89 was $2.05 and 93 was $2.27. I've noticed my MPG is a bit higher in the city, like 25.5+ vs 23.5 on only 89 octane, so it is probably a break even on the cost vs the additional MPG. I'm on my third blended tank now so I'll keep checking the MPG.
And it is a lot more fun then a base model for sure!
