Is Premium Unleaded Necessary?

[XLRVIII]

I was told once by a reliable source, that the "octane plug" is not always what it says it is.

true, on most mark 8's removing the spout will decrease timing by 3 degree's..which sucks
there were a few pcms that would add 3 degree's.

the beauty of the spout is that if you have the SCT software you can dictate what the spout does, and could open or close that connection with a toggle switch or momentary WOT switch.

 

[DLF]

Not spout, which on some older cars, bypasses the DIS and locks the timing @ 10 degrees BTDC.

Octane adjust plug

Which, BTW, does absolutely nothing in the stock '98 BTC0 tune, as the "Octane Plug Spark Modifier" table that it controls is filled with zeros.

Usefull at the track though with SCT software. I use it to add 2 degrees timing on my SC when running race gas. Add 102 octane unleaded and pull the plug.