Your car has a low enough compression that 87 will work perfectly. The truth is if the engine is designed to run on 86 or 87, 93 might not even completely ignite and you might suffer a loss of efficiency plus the extra cost. On the subject of the trim level the EX and LX models share the same 150hp V-tec engines, only the DX has a 135hp with no V-tec. The V6 came in LX and EX and put out 200hp with Vtec.