I've fooled around with fuel octanes in the Solara and found the 93 octane (readily available around here) is BOTH conducive of better performance (incremental, but it's there) AND better mileage (upwards of about 1mpg or a tad more in cases) from carefully measuring my results on multiple trips. It doesn't make up for the cost of premium altogether, but it DOES offset a portion of it, and if you add in the performance increase, it's worth it to me.
I always run premium in the Solara and my Supra. Now, in my TUNDRA, I've found it runs JUST AS STRONG and JUST AS GOOD (or poor) MILEAGE with 87 octane as 93, so with a 26 gallon tank that drains so fast it's like there is a HOLE in it, I always run the 87 and have no issue and good performance and... well... mileage will NEVER be great with the big, 5.7 liter V8! HA! It's a blast to drive all the same!
-crisp