Like you I only use premium 93 in the Porsche and in my 2016 BMW 335i which also calls for premium. Amazingly our 2017 VW GTI only requires 87 regular, although VW does say that you lose some power by not running 93. I guess if I was tracking it I would run premium but for my wife and daughter driving it regular is probably fine. Not sure if that is US only or rest of world too. GTI’s before 2016 required premium fuel but basically the same engine.
Daryll

 

I recently switched from Mobil Supreme to Shell V-Power.

At idle with the Mobil gas, there would be random noticeable "stumbles". They were annoying but once the engine started to rev pulling away it ran fine.

With the Shell 93, the engine idle is now smoother and improved even more after a couple of tank-fulls.

We'll see how it does in the next few weeks.

BTW, my car has the low RPM "stumble" which varies randomly. Go figure. I ignore it.

 

In most cases if the octane is the same the only major difference between major brands is the additive. More often than not they are loaded at the same terminal and then the additive is put in for whatever brand they are delivering. By measuring the level of the additives in our gasoline they can tell whether we are slipping in cheaper unbranded gasoline and violating our sales agreement. We've only been tested once in our 25 years but it may be something they do in large markets with large volume stations.
Since I'm a Shell dealer though, I'm happy it's working for you!

 

The octane rating itself does nothing to increase performance (in fact, higher octane fuel is actually more difficult to ignite). Modern cars (like the 996) have knock sensors and will advance the ignition to the maximum limit the octane you are running can handle, so they typically will have higher performance with higher octane fuel, but also (in theory) should be able to run lower octane without damaging the engine. If anybody has run low octane fuel in their 996, I'd also be interested in hearing how performance compared to premium. It would also be interesting to hear if the 996 knock sensors completely eliminate pinging with low octane fuel.

Running too low of octane for a car without knock sensors, or if knock sensors aren't perfect in preventing pinging, is actually pretty damaging to the engine over the long term. That pinging sound is the cylinder firing too early, before the spark plug fires, because the low octane fuel self-ignites from heat and high pressure alone. That early ignition creates a significant downward force on the piston top while the crankshaft momentum is still pushing the piston up. Pinging sounds fairly harmless, but If you think about what is really happening on a physical level when pinging occurs, you realize it's a very bad thing.

 

Usually you only find 93 sold at lower altitudes, and 91 at higher altitudes,,
Has to do with vapor pressure,,

if you measure the cylinder flame front temp, (Not at home... LOL)
For the most part... (there are exceptions)
87 is hotter than 89
89 is hotter than 91 and
91 is hotter than 93

So the big difference is head temperature control.
Which leads to tuning control.

I converted a dwarf car with a GSXR 1350 (Stroked and bored 1100 AIr cooled) to Methanol,
the cylinder head temps at full run dropped from 600 to 325..
On a cool day I had to put a salamander on the darn thing before we went out to race..

 

I have exact same running description, small random stumbles by a cylinder. great throttle response, free revs. just annoying.

I used to use Shell in all; Targa, MB, and Toyotas. I just seem to have a higher sulphur smell when using it.

 

Meth + 996 = ?

 

My shell station in Chicago is also 93. And it’s getting $$$ these days.

 

= arrested!