I just spend the extra buck or two and go for the premium. Probably doesn't need it, but I feel better about it.
You might feel better, but your wallet doesn't.
Here in Canada many of the gas stations used "good better best" to describe the fuel grades, which was a lie because putting higher octane fuel in an engine that is tuned for 87, will not benefit anyone except the fuel companies and didn't make your engine run much "better". Using higher octane than recommended generally doesn't make your engine perform any better if it's not tuned for the delayed detonation with higher compression ratios. Due to less ethanol, you might get a slight bump in mpg so you can drive further on a tank, but the cost of the 91 fuel is greater than the savings of increased range in mileage, so you're actually wasting money. After complaints from the public, the companies advertise the fuel grades claiming more fuel additives to clean your engine today, which is still misleading because people think the higher grades clean better but they really don't. It's still just a way to try to sell more expensive fuel that you don't need and not get in trouble with advertising.
Here in Canada 89 and 91 are priced at a higher premium rate than in the US too. As an example, right across the border in NY state a gallon of 87 is $3.79 and 91 is $4.49, that's a 70 cent difference. Here in Canada the same example is 23 cents per liter more which is 87 cents more per gallon (0.23 x 3.78 - a gallon is ~3.78 liters). We also pay a lot more tax at the pump so today's price is 1.63 x 3.78 = $6.16 a gallon, about 37% more. So when visitors from NY come to Ontario, they get to pay 37% more for fuel.
Welcome to Canaduh.