Is STP Octane booster worth it?

[Mpgingerson]

I drive a Legacy 93 EJ20G and I've only filled it up with Shell V Power 98 Octane and is it worth it to buy an octane booster from time to time? And one other thing.. I'm very stoked about weight reduction and some people is saying that filling the car up 2/4 or 1/4 will increase MPG/performance. Is this true, I mean it kind of makes sense due to the weight of the petrol.

[mike-tracy]

The octane boosters do work if you use sufficient quantity. If you're just adding a few OZ to your fuel tank then you are really only adding 1/64 ot less of an octane point. Also, if your ecu is tuned to a particular octane, raising it above thsy is only going to have minimal (and probibly not noticeable) affect. So putting half a tank of premium and half of race gas won't make a worthwhile difference.

Lowering the weight of your car for more performance? Sure! The fuel pump is liquid cooled (ie by the fuel) so you dont want to run on fumes or it might burn up. You could also take out the rear seats, head liner, jack and spare tire, the "gf or wifey," go on a diet, remove the complete sunroof assembly (it weights over 50 lbs) and replace with a panel. A guy sells carbon fiber 'sunroof deletes' in the vender section, along with ridiculously awesome C.F. hoods. Smaller wheels will save you a bunch of weight too.

[mike-tracy]

Also, removing the AC pump and condenser should save you 40lbs or so

[MConte05]

Removing weight will do way more than octane booster. I had to run some and mix in race fuel in the rally car due to knock issues from too much timing with a unique engine setup. But once properly tuned won't need it.

Weight is the biggest one. My open class legacy weighs around 2750lbs even with a roll cage in it. I have barely any front beam (supports the lights and intercooler), no rear beam, gutted rear doors, gutted dash, wiring trimmed down, trunk lid gutted, hood gutted, etc. Combine that with a 250whp (ish) EJ20G with a twinscroll turbo and short ratio 4.44 gears.... It's a rocket.

[Mpgingerson]

Okay, I'll skip the octane boosters and instead use some sort of injector cleaner from time to time, but it looks like I've shed all the weight I can at the moment. I still want the car to be really function friendly, and when I want to, go full race car mode haha, but thanks guys!

[Legacy777]

Seafoam is the fuel system cleaner I'd recommend.