Fuel Additives
 

The Boxster manual states not to use fuel additives.

Have you used any fuel additives? If so, which brand do you use?

Why does the manual state to not use any fuel additives? Many fueling stations already incorporate additives in their pumps?

Buy the highest octane (91 or 93) that you can from a busy national chain and don't worry.

If you want (and I do) use the Chevron Fuel System Cleaner BEFORE every oil change. Add to your full tank about 300-400 miles before your change, run it down, refill, and go get an oil change.

For winter storage, I use 1 ounce StaBil per 2.5 gallons fuel.

That's it.

Compatibility mostly, not all additives play well with each other.

The only fuel additive PCNA ever sanctioned using is Techron, which is a system cleaner, not a performance additive.

If you are buy quality fuel, it already has additives in it.

What kind of fuel additive do you want to use? Something to CLEAN the fuel system? If that's the case, as JFP mentioned, Techron is as good as any and better than most. And it's already in the fuel, if you buy that way.

IF you're looking for some sort of performance increase (including consumption) from an additive, you're wasting your $$. (assuming your motor is stock, or mostly-so.)

The best advice is below: Buy High Quality fuel from a busy station. This ensures the fuel is relatively "fresh" and clean.

While working at Saleen & Shelby American I assisted 2 different EPA Certification engineers to get the cars EPA certified. Both engineers insisted on never using anything but Chevron Supreme fuel in the vehicles until they passed. That's all I put in my cars to this day.

I've always used Techron in my Boxster. Have I had any issues? No. Have I seen any benefit? That's a difficult question to answer, as I have no baseline to compare to. Why do I keep using a product that I cannot verify any gains? Because I'm a creature of habit. Do I enjoy wasting money? I suppose so, if it provides some deterrent to the "wish I would have kept using Techron" scenario that I might encounter in the future...but then again, I don't see it as a "waste", more of a proactive payment. Do I use Techron in my other vehicles? No. Why not? Because I'm not hopelessly stupid, just partially so. ;)

Great input. I was thinking about using BG 44k fuel system cleaner.

I was always told to put a bottle of Techron in my gas tank well before my planned oil change. Run that tank down and likewise the next tank. Then dump the oil that may have been diluted by blow-by with the Techron additives and injector cleansers. Put in new oil after a complete drain. Do it before you put the car into hibernation for the winter.