Hmm. There's a big array in Adafruit_SSD1306.cpp:
static uint8_t buffer[SSD1306_LCDHEIGHT * SSD1306_LCDWIDTH / 8] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
:
You could try just getting rid of the initializing data (what a waste of FLASH. Sigh.)
static uint8_t buffer[SSD1306_LCDHEIGHT * SSD1306_LCDWIDTH / 8];