is-90-the-same-as-91

is 90 the same as 91 is 90 octane the same as 91 is 90 gas the same as 91 is it ok to use 89 instead of 91 is 91 the same as 93 what happens if i put 93 instead of 91 can i use 95 instead of 91 using 89 instead of 91