Does a 99 Civic Si require 91 Octane or higher, or is 87 Octane ok for it and not going to do damage to the motor? Thanks

 

I want to say that 87's fine, but I'm not sure... do you have the owner's manual handy? If so, read through it; it'll say what the car needs.

 

if you look on the fuel doorit says right in it run premium fuel only....i had a 00 Si and all i ran was premium the car wont run very good on anything less then 91

 

You actually need 93 or the highest your gas station has. Anything less and you risk damaging the engine

 

Yeah the owners manual says 91, but ive been running 87 and its been running fine no sputtering, i cant hear the valves tapping, nothing of the sort.

 

You need to run what is recommended for your car. Is saving 10 damn cents at the gas pump really worth the risk of significantly reducing the longevity of your car? [:@]

 

Remeber Tony when people put 87 in a car that needs 91 they are thinking of the now, not the future. lets just kick back and wait for the crying and selfass kicking

 

99 si has 10.4 : 1 compression and you wouldnt hear valves tapping but you could hear pinging which means detonation and engine damage Ionly run93 on my b16a engine. Besides the gas mileage you will lose on saving that 20 cents a gallon by not running premium as recommended is actually worse for your wallet any way youlook at it.

 

My dad had a BMW 740 or something like that a while back and he insisted on putting 87 octane in it when it called for 91. He was the same as you "its fine, no noise".... whatever. At about 238000 km (sorry, i'm not in miles) the motor threw a rod on the highway and became not worth it to fix.

Using lower octane SLIGHTLY changes the timing on your car, so slightly you wouldnt notice, but it does have a bad long term effect, as my dads BMW, which he drove like a grandma, throw a rod and pretty much blew up.