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Fuel Quality

J

John Maddox

New member
Looking at Porsche Post this month on this topic (thanks Maurice) I wonder if anyone else has views.

I have tried Optimax/BP/Esso/Total/Tesco special 97+ Octanes and find little discernable difference.

I live in a predominately retirement area and my theory is that the local Petrol Stations sell very little of the special fuels to the locals and hence the fuel I buy is relatively old.

Fuel looses it's octane value over time so I reckon there is little difference between fresh 95 and the older special fuels.

Anybody an expert in this field who can give a view ?
 
You're absolutely correct about fuel degrading and being less efficient. I understood it to be a roughly 6 months for it to get to a state of wanting and therefore not worth using.

You mention that you've tested various types of fuel, over what sort of period did you test them?

I have done a similar exercise but only against Shell Optimax and Shell regular. There was no obvious difference however over the course of about 3 months I did notice my fuel economy go up using Optimax. Using them for a week or 2 had no effect.
 
John
I hope you are driving sensibly in the retirment area, I recently stuck this on the Turbo forum

When I got mine without a handbook in English I was advised that I could get away with 95 ron if I wasnt going to be racing it all the time. I tried a full tank or two of Optimax(£90!! , long range tank)and didnt notice any difference.
After a few thousand clicks and being much more aware of the sound and feel of the car, I noticed when my foot was flat on the floor I could feel a slight bits of hesitation(?pinking) in the top end of the turbo rev range so I tried out the Optimax again and found that this went away(so I presume it was the knock sensor etc) I also found that I was also getting nearly 2 mpg extra!

So definately use the good stuff as it works out cheaper when considering mpg and performance. Only thing to be aware of is that some of the testing on super unleaded has noticed that it starts todegrade after a few weeks sat in the pumps so use a high volume station, which happily coincides with normally the cheapest.
 
Just a quick thought, if you have had your car remapped on 98 ron super unleaded then keep running it on super as the safety margin may have been taken up by the mapper.

I had my car mapped (by mistake) on a tank of fuel with octane booster in it so it was closer to racing fuel, then ran it on optimax - 1. 1 track days later it needed new pistons, barrells, and a head, ouch due to big style melt down :-(

You will be OK on a std engine but if you have had it tuned in any way stay with high octane fuel

John
 
Thanks guys - interesting points.

I did not do a scientific test but used higher octane fuels for a few months and subjectively did not notice any difference in performance or mpg.

My 993 has done 156,000 miles so perhaps the compression ratio isn't what it once was!! and this is masking any improvement.

Still goes very well though.
 
Talking to a proprietor of a Shell station recently who informed me that with Optimax the retailer has to send a tank sample off every 10 days back to the refinery to establish that there is sufficient turnover and little or no degredation of the fuel. i guess the same applies to those doing low mileage with a tank full of fuel. There was a very good article on fuel in one of the monthly magazines last month (will try and remember which one). It was an interview with a guy from Shell and was very informative. Seems that with the higher octane fuels the additives vary from European Country to Country based on average ambient temperatures etc. Went on to say that they have different fuel blends for their racing fuels as they move around the globe depending again on temperature etc.He also stated the fuel companies effectively buy from each other depending on whos got what and where they have got it stored in the UK at any particular time. Went on to say that the unique brand addatives where added to the fuel at the point the tanker is loaded. Seems that one of the purported qualities of the additives in Optimax is to give a far quicker initial ignition and combustion time when compared to ordinary Super.

Mike Cooper
 
Be wary of relying on a single manufacturer (or fuel) and expecting consistent results. Saw recent correspondence (Can't now recall whether it was The SUnday Times Motoring, Evo or Circuit Driver magazine or similar) which confirmed that they do sometimes cross-supply so you can have Esso (or other) fuel in a Shell pump. Assume that if Shell are selling it as 97Ron then would have to be 97 Ron whatever the source otherwise would fall foul of trade descriptions legislation.

The other tip from Evo (echoed by an earlier thread reply) was to use a well-frequented petrol station so you have a high turnover and a good chance of getting fresh petrol.
 
Hi,

The interview was in EVO, with Mike Copson from Shell.

The petrol companies do cross sell from different refineries, to avoid having to truck fuel across the whole country. Normal 95 Unleaded is made to the same standard by all companies, with company specific additives being the only differentiation. These additives are added to each batch of fuel as it is loaded into the tankers, so that petrol refined by Esso becomes "BP" Fuel etc

Optimax, however, is only made in Stanlow refinery in Cheshire, and is not shared with other fuel companies.

In the EVO interview, Mike Copson did state that fuel "weathers" with age, presumably as the additives either evaporate or react with each other, so it is better to get the fuel from a busy station with a good turnover of Optimax

Pete
 
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