I have a 89 with a large street port and rb header, high flow cat, and exhaust, Blitz intake dual pulleys. should i still use 87

 

On a S4? Yes still use 87 octane. There is no need to increase octane unless you have upped compression or boost. If you have done neither dont worry about octane.

 

sweet, 87 is so cheap compared to 93 these days

 

shoot an n/a periferial port should probobly still use 87. it might even help sinca at those cimd of rpms there is very little time for each ignition event to occur.


i swear the oil companies have brainwashed amercia in to blindly thinking premium gas is inherently better when t is fact worse for about 90% of the cars out there.

unless you have 1O.5:1<compression, or forced induction, YOU DONT NEED PREMIUM!!!!!

 

80 is best i wish we had that at the pumps when i had my n/a

 

Ya non-turbo 13Bs were designed by Mazda to run lower octane than 87 octane, somewhere around 83. Unless you have FI or raised compression, dont worry about it.