I run Chevron 93 in the S14 (when she's deciding to run) and anyone's 87 in the S13. Big bad tahoe gets big bad 87 lol. If the S13 had a motor in better shape, I would probably stick to the Chevron 93 in her as well, but the motor in there is just about shot.

As someone who drives imports, the price difference doesn't make too much difference... an 11 gallon tank, I'm paying anywhere from $2-$5 per TANK difference, depending on how gas stations have their prices setup. A tank lasts me about 2 weeks. The day I'm too broke to afford about $10 a month difference in gas is the day I go back to one car.