Super-unleaded or unleaded?

[richrack]

I drive a 987.2 Boxster S, and when I picked up the car, the Porsche dealer told me I just need regular unleaded petrol. I asked about Super-unleaded, and he said that only turbo-engined Porsches need super. For my kind of mostly "sensible" driving, unleaded seems fine - I mostly use Shell. I have occasionally tried super (Shell V-Power), but for day-to-day driving could not feel any difference, or notice any difference in fuel consumption. Maybe I'm not driving fast enough to tell!

I intend to keep the car for a long time, so want to make sure its the right choice. Any views on choosing between unleaded and super?

[ORD]

Buy super. Shell is probably the best. It is better for the engine and anyone who says otherwise is s cheapo

[rObArtes]

yep 98RON all the way

[HappyBoxster]

I have the same car and I was given the same advice from the OPC. Use normal.

On the off chance that this is simply the same 'rogue' OPC then it might be useful to know that I purchased from Bournemouth.

[nsm3]

RTFM

Failing that, see what it says on the sticker inside your fuel filler cap.

Normal doesn't harm the car, but the knock sensors retard the ignition and lower performance.

If you don't extend the engine, you probably won't notice?

[sidicks]

richrack said:

I intend to keep the car for a long time, so want to make sure its the right choice. Any views on choosing between unleaded and super?

What does it say in the manual and on the inside of the fuel flap...??

[billzeebub]

Shell Vpower every time

[Rockster]

nsm3 said:

RTFM

Failing that, see what it says on the sticker inside your fuel filler cap.

Normal doesn't harm the car, but the knock sensors retard the ignition and lower performance.

If you don't extend the engine, you probably won't notice?

Actually if using something less than the proper octane grade of gasoline the engine's timing is most likely to be retarded at part throttle operation. It is at part throttle relatively high load operation where the timing would be most advanced. This advance gives the burning charge time to get going so as to develop max. pressure in the cylinder and generate the most work from burning the mixture.

(One can see this, observe it by using an OBD2 scan tool to observe/monitor ignition advance in real time. At part throttle low speed operation timing advance can climb to 34 to 36 degs. before top dead center. Running this much advance really makes a difference in the engine's responsiveness and helps gas mileage too.

Running less than the proper octane grade of gasoline in the engine is false economy. While the fuel costs less the miles per gallons is worse and to add insult to injury the exhaust gas temperature is raised which subjects all components in contact with this to higher operating temperatures which can only shorten their service life.

Oh, and the higher octane fuel has a better detergent package which helps keep fuel systems and engine components from building up harmful deposits.

[NicD]

How long for the ECU to adapt to 98 after using standard? is it reset and sampled for each start up, or averaged over a period?

[ORD]

NicD said:

How long for the ECU to adapt to 98 after using standard? is it reset and sampled for each start up, or averaged over a period?

Consensus on here was that on recent Porsches it will adjust after a short while - someone mentioned 1/4 of a tank as a rough guess.

OPCs saying to use regular fuel is so worrying that I don't like to think about it. Idiots. It would also probably ps off Porsche to know that their dealers contradict what it says in the manual.

[BIRMA]

Apart from the higher octane I use it because of it's cleaning additives.

[graemel]

Shell V Power Nitro every time. Within the last thread on this it was the turbo charged cars that noticed an increase in performance. It made a very big difference to how my super charged truck runs.

[mrdemon]

rObArtes said:

yep 98RON all the way

I only use 99Ron :-)

[nsm3]

I only use 97, as that is all I can find locally.

[ORD]

I think, rightly or wrongly, that I can feel the difference, esp at low revs.

[NicD]

thanks ORD, I will switch to Shell VN for next fill up.

The car (987.2 S PDK ) is used mainly for outer London commuting, so lots of low rev work.

It feels very smooth and responsive now, but will be delighted if this improves.

I always filled my GT3 with high octane but haven't always been able to with my Boxsters.

Now fuel price declining a little, won't be so painful.

Nic

[richrack]

Thanks to all for the feedback. I'm tempted to keep to Super from now on.

The Drivers Manual says "The engine is designed to provide optimum performance and fuel consumption if unleaded fuel with 98 RON is used. If unleaded premium fuels with octane numbers of at least 95 RON are used, the engine's knock control automatically adapts the ignition timing."

So I suppose that the dealer is right, as the car can be driven on 95 RON fuel, although it won't produce "optimum performance". Acceleration is also subjective - the car will always feed a lot quicker down a narrow country lane than on a motorway! So I guess what I was asking - can anyone really feel the difference in performance in day-to-day driving, or notice any difference in fuel consumption?

[thegoose]

The best way to notice the difference straight away is to fill with Vpower then have the adaptions reset on Porsche diagnostics, so that the car's expecting the correct high grade fuel.

The car's computers will adapt quickly to low grade fuel, but are slow to adapt to high grade again, hence people saying they tried changing and didn't notice a difference. The difference occurs gradually, in both performance and mpg.

I don't think the OPC are right at all about this - here we are, sir, the representative of the brand, the OPC network is the pinnacle don't you know but, err, ignore what Porsche say and fill up with any old fuel just like you would an econobox, that's what we do, I mean, it's not like the brand's built on a reputation for performance is it? So what if it doesn't run as well as it might, you'll save 2 or 3 pounds each time you fill up.

[mollytherocker]

Spending serious money on a Porsche and then putting lower octane fuel in it, to me, is very strange behaviour!

[Callughan]

Porsche West London fill up their cars with unleaded.

I used to especially notice a difference on the 996. A couple of times when I put in 95 it didn't feel as responsive.