What is the format of the number on the can bus? The code you posted appears to be dividing by 10 to convert an integer representation of a float to an actual float. If that is the case, you do not need to use String or float to do the printing, it can all be done using integers.
Which library are you using for the display? Adafruit's libraries for OLED displays typically allocate the memory for the display buffer at runtime, so it does not show up in the ram usage from the compiler. If that is the case, you are definitely out of memory.