Premium Gas?
 

I saw a note in The Week magazine stating: "Some manufacturers stipulate that premium gas must be used in their vehicles, but no manufacturer Consumer Reports has questioned has tied the use of premium to a vehicle's reliability, only to its performance. We suggest using premium only if the alternative leaves your engine pinging or seeming sluggish.
Premium is merely a recommendation for many vehicles and recent track tests of two of them showed no difference in performance when regular gas was used. Fuel economy and 0-60-mph times were identical.
Though octane levels appear to matter little, quality does. Many major gas station brands sell only "Top Tier" detergent gasoline. Avoid anything but Top Tier to keep your engine clean and running smoothly.

Granted, the note does not indicate which manufacturers were queried, but what do we think?

The Boxster has a very high compression ratio for its age, high enough that it retards timing when the clutch is disengaged because the sudden rev drop could cause knock. I wouldn't play with lowering the octane on that. With all the quirks the M96 already has, why mess with pre-detonation?

The 986 has an 11.0:1 compression ratio, the same as a Ferrari 360 Modena and a Lamborghini Murcielago.

Many cars that "recommend" 91+octane are just hot versions of economy cars, with compression between 8-10:1 and the rest of the difference made up by timing or boost. With electronic spark control, the car can easily back off timing if fed regular fuel, and run like a base model. Some non-sports luxury cars might only call for premium to keep the engine clean, after all being stranded in the middle of nowhere because you can't find 93-octane isn't a very luxurious experience.

But the Boxster and the M96 are both designed from the ground up for performance, it's not an up-tuned version of an engine that runs on 87 and certainly not designed to be low-maintenance.

Of course, I haven't tried running less-than-recommended fuel, but I have a strong inclination that you shouldn't try it, either.

You can find top tier stations here

https://www.toptiergas.com/

Yes it does make a difference in performance and deposit buildup. Gas is not a shelf stable product and keeping your gas tank full and mileage low is not good for your Porsche.

Premium only! Regular octane fuel is garbage. I run premium in everything, especially small engines.
(Mech engineering experience talking)

Well. This Mech Engineer runs regular in everything except the K100 RS, which has no knock sensors. But my 986 only has 193,000 miles on the clock, so I’m just a noob.

The 986….
 

…..and all modern cars have knock sensors and can run 87 octane unless you see a label on the fuel filler cap that says, “MUST” use a specific octane.

If it is just a “recommended” label, then you are fine with 87.

Now, that part of it is just the knock and damaging engine part of it.

The detergent part of it is less exact. Many companies only put their best fuel additives in their premium fuel.

But, you can fill up on 87 and drop a bottle of Techron or Red Line or Driven fuel injector cleaner in the tank and you will be fine.

Of course, that brings the cost up to just buying premium fuel.

Don’t overthink it.

The OP doesn't mention WHY they want to use regular instread of premium. I assume it's because of the price difference.

For arguements sake, let's say premium is $1 / gallon more expensive than regular. A fill-up will cost you a whole $15 more for premium. If you're scraping to save $15 once or twice a mo, a Boxster may not be the proper vehicle for you.

Where we live SoCal, and usually the difference between Premium and Regular is about $5 (max) per tank, and needless to say, we always use Premium in all the cars..

I use diesel in my Boxster. :cheers::D:matchup::barf::p

Wow!

Move to Nebraska. It's generally 50-75 cents at most difference. Thought I was being generous at $1 (and it made the math simple).

The Costco in my area sells Top Tier gasoline for prices that are competitive with most of the unbranded gasoline stations. Premium is $3.64 and Regular is $3.16 today. The $0.48 cost difference is typical, but it does vary.

The owner's manuals for my 2005 Mercedes C230 says Premium is required. I think the manual for my Boxster says the same thing. I expect both cars would run on Regular, but I also expect the fuel economy would decline. Based on this, I decided that saving a few dollars per fill by using Regular would not have a huge impact on overall operating costs.

Because German cars in general seem to be maintenance and repair intensive, I decided to eliminate a risk factor and pay extra for Premium fuel.

Well, for some of us, that would be $15 a week, and that’s reasonably serious beer money.

At one time, not too incredibly long age, I believe that PCNA had a statement on their website noting that regular fuel was just fine, given modern engine controls.