Exxon 93 octane.

 

76 Union 91 Octane in both the p-car and the wife's audi.

 

No way to really know but generally discount gas retailers have to have some way of keeping a profit margin while selling gas at a discount compared to name brand stations and one way is to buy cheaper gas and cheaper gas is a gas with fewer additives.

When gas prices were high not that long ago word was some major name brand stations were operating at nearly a zero profit margin due to the high cost of gas they were required to buy/stock. Some owners claimed that they kept selling gas even at nearly no profit just to bring people in for the purchases they made in the store. Almost everyone who walks into a gas station comes out with something besides a receipt for gas.

76 is a good gas based on my unscientific experience. My cars run ok on it along with Chevron, Shell and USA, Rotten Robbie and Quik Trip (back east) and various truck stop gas stations that I use when I travel long distances.

BP and Exxon are not stations I encounter and tend to not buy gas from them when I do. Nor do I buy gas from discount outlets on Safeway, Wal-Mart or Costco parking lots.

I do not buy Arco gas and do not like its gas stations. The gas may be ok (though discounted it comes in for suspicion regarding its additive package) but I do not like having to use cash to buy gas and I do not use a debit card and the stations don't take credit cards.

Valero gas I avoid. Valero's claim to fame is its refineriers can refine the lower grades of crude and whle gas is gas (has to adhere to certain characteristics) I just don't feel right buying gas at these stations.

A UK published car mag (Evo IIRC) did a test of gasolines in the UK a while back. Found considerable differences between various brands of the same grade of gasolines. The brands don't map well to USA gasoline stations but one interesting thing that came out of the test was gasoline can go stale.

Gasoline can go stale, be stale. There were differences (measured on a dyno and with an experience race car driver on a test track (using the same car for each gas) between the same gasolines bought at different times from the same stations and different stations and staleness was the reason. Premium gas having more additivies than the lesser grades of gasoline has more to lose over time than the lesser grades of gasoline. Just a few weeks can see premium gas go off. It still is premium -- though it might have lost some octane points to account for the reduction in power and torque the testing found -- but the important additive package deteriorates.

The advice Evo offered was to buy a name brand gas and buy from a busy station to help ensure getting the freshest gasoline. A bonus is generally a busy station is one offering gas at a lower price so you get fresh gas and save a few pennies/gallon.

Sincerely,

Macster.

 

From my 356 research, I do think that ethanol degrades, so I do agree with trying to get fresh gas. I would never run with less than premium, wish I could get 93 vs. the 91 available in CA, and have in the past added some 100 for the helluva of it but never really went for a run that would let me decide if it was worth it.

 

ALWAYS Chevron 94 Octane when in town.

 

I generally choose Chevron 94, but will use most other retailers' premium grade if I'm on empty and a Chevron isn't conveniently nearby.

By the way, it was my understanding that often gas for different retailers is delivered from the same refinery, depending on geographical region. So the gas you buy in one area, may all be essentially the same, with the only variation perhaps being specific additives etc.

 

Djlod,

Here's why you should not use low octane fuel on high performance engines.

Low octane fuel combust very fast, explodes instantly hence you'll hear knocks on the engine. High octane combust spontaneusly(slower than just exploding instantly) which pushes the pistons steadily.

You won’t hear the knocking because the engine has the anti-knock system. It retards the timing as soon as it senses knocking and won't let you accelerate as hard because its sensing the fuel is detonating(lower octane) instead of spontaneously combusting(higher octane). Knocking is caused by lower octane fuel properties, which explodes swiftly, and causes the rattling on the valves, lifters and pistons, instead of combusting spontaneously which the Porsche engineered for. For the engine not sustain damage from knocking, they installed the knock sensors, which retards the timing in the expense of performance but do prevent damage.

Bottom line is, the ECU(engine control unit) will not let the engine accelerate as hard as it would if it had higher octane fuel. Hence the "for Optimum Performance use premium fuel" verbage in the owners manual.

 

what about Sunoco 94?? Any opinions?

 

I was wondering about Sunoco 94 also myself.
But it seems like, at least in my area anyway, that Sunocos are everywhere and often hole-in-the-wall looking convenience stations, so I've hesitated.

 

Sunoco 93...she never says "no".

 

I used Shell and about a year ago switched to Chevron.

 

91 is the top available here. And, as to it not making any difference, many years ago, as an impecunious student, I destroyed the valves in the high-compression engine of my first (non-Porsche) sports car by deciding that I could only afford regular gas, rather than the premium it was supposed to have. I won't make that mistake again.

Regarding the difference between 'brand-name' and 'no-name' gas, I have often seen tankers finish their delivery at a local brand-name station and then drive across the street to deliver to the cheaper, no-name station on the opposite corner.

 

Thanks for the reply.
I will show this to my colleague who uses the cheap stuff in his P car.

 

Great reply.
Thanks Mike.

 

Gas is a fungible commodity.

Exxon's product probably rides in the same pipe as Shell's until it gets to the terminal. Then they add their 'handful of oats to the silo" so marketing can spin it.

It's all about the money.

BD