premium gas?

[husker boxster]

So to stir the pot a bit more, which would be better?

91 octane
or
93 octane with 10% ethanol

We only had 91 around here but saw the 93 blend recently.

[nieuwhzn]

Trying to save a couple of bucks by filling up with lower octane doesn't work for high(er) performance cars. The ECU will just adapt the mixture so that the engine power stays the same. Lower octane will lead to lower mileage. We've been driving Saabs for many years and decided that the highest octane will cost the same in the long run and results in a smoother engine.

[Dale_K]

I'm new to Posches but my other vehicles built within the past 15 years all have knock sensors that detect motor knock and adjust the ignition timing as needed to prevent it. Can anybody confirm whether or not Porsches have knock sensors? Does the 2000 S model like the one I bought a month ago have them?

I doubt I would use regular gas anyway but it would be nice to know whether the engine can actually be damaged on low octane fuel. I've used regular in my Corvette and couldn't hear any knock or feel any power loss but I decided high test would only cost me about $100 a year and there was no point to the cheaper gas.

[Topless]

Originally Posted by Dale_K

I'm new to Posches but my other vehicles built within the past 15 years all have knock sensors that detect motor knock and adjust the ignition timing as needed to prevent it. Can anybody confirm whether or not Porsches have knock sensors? Does the 2000 S model like the one I bought a month ago have them?

Yes the Boxster does have knock sensors and by design your smart ECU will retard the timing to prevent detonation and engine damage. It is a band-aid that should not be relied upon every day but it is there to prevent damage in the event that you put 87 gas in. Performance and mileage will also suffer with retarded timing due to the knock sensor so you won't save any money running cheap gas.

[Flavor 987S]

Originally Posted by husker boxster

So to stir the pot a bit more, which would be better?

91 octane
or
93 octane with 10% ethanol

We only had 91 around here but saw the 93 blend recently.

You will get better MPG's with the 91 octane (no ethanol) vs the 93 (with 10% ethanol). Did this experiment last year. 93 is probably still the best bet. 93 pure gas (no ethanol) is ideal. It is very easy to find in places like Wisconsin, maybe due to all of the RV's and boaters.

[SeanZ4]

Dale K, look in your trunk (back one) and you should have a sticker in the middle that says your car has knock sensors etc. I have a 2000 S and it does.

The most we can get is 91. Which really surprises me with all the farm equipment etc. Actually that's just given me a thought. I'm going to check the non-tax co-ops. I'll bet they have higher octane. For those out there that must have the torpedo-juice stuff, why don't you consider your local airport?? I know ours will probably sell the av-gas. So just fill'er up with the blue stuff! (disclaimer: I'm sure this isn't a good idea)

sean

[lifeisgood]

How about a bottle of octane booster add to the tank? Any suggestions?

[tamarsha]

When I had FVD build my ECU mapping I made sure to tell them all of my mods and that run 93 octane exclusively. I assume they tweeked it a little to take advantage of that.

There is one gas station near me that sell 100% gas. I try to go by there when I can. It is a little more expense but if you do the math…

Ethanol has about 75% the caloric value as gas… At most stations, 10% of the gas is Ethanol… that is 97.5% the “power” of 100% gas.

A 280 Hp Boxster S will see a 7 Hp gain running 100% gas over a 10% Ethanol mix. Is that worth an extra $0.10 a gallon or $1.50 a tank? Less than $0.40 / Hp gain. Show me a better deal out there.

[clickman]

I have heard that the ethanol mix is much harder on fuel system components.

[husker boxster]

Originally Posted by clickman

I have heard that the ethanol mix is much harder on fuel system components.

That's an old wife's tale from the problems in the 70's when ethanol first appeared. With 30 yrs of development under their belts, automakers wouldn't put components on their cars that can't handle ethanol.

Kind of like graphite shafts in your golf clubs. People still say they may be inconsistant. Was true when they first came out 25 yrs ago but there's too much technology out there now for that to be true today.

[tuanle16]

Originally Posted by lifeisgood

How about a bottle of octane booster add to the tank? Any suggestions?

what are poeple's thoughts on this. just adding a bottle of octane booster to fuel? and is fuel injector cleaner an absolute NO-NO?

[blue2000s]

Use premium gas. The engine can't take advantage of an octane level higher than what it was designed for, which is premium.

Porsche allows for the used of injector cleaners with techron but generally discourages cleaners or additives.

[laphan]

Originally Posted by husker boxster

So to stir the pot a bit more, which would be better?

91 octane
or
93 octane with 10% ethanol

We only had 91 around here but saw the 93 blend recently.

I did this experiment with my previous car (toyota solara). The car recommends 91 octane (but can take 87 with some engine output reduction/increase fuel consumption per owners manual). I put 91 un-oxygenated fuel when I was in Minnesota and I put 93 with ethanol when I moved to MI. No noticeable power difference, but 91 with no ethanol returns at least 2-3 MPG better on highway.