Hi you all,

Silly me, when I bought my car, I forgot to ask what fuel she's used to.
First petrol station visit, I looked like a fool trying to decide what to quench her thirst with.
I opted for 95 and settled at $120+ for a full tank.

I later contacted the past owner who admitted to the 91 long held option.

As a good owner, I want to do it right.

My question here: What's best for my car?!

Anyone, an opinion?.. .

 

Hello Laurence....don't know if your query has been asnwered but I believe it's not a good idea to use cheap fuel or 91 octane, as most of this rubbish comes from Indonesia and contains as much as 10-15% ethanol which is not good.
Steer clear of United or independant fuel outlets.
Stick to recognised brands and the correct fuel to use is 95 octane.
98 is OK to use for the occassional clean up but is really a waste of money.
I get 10.4 litrs/100klm from my '98 XJ8 on 95 octane.

Cheers,
Maximus

 

The octane rating of fuel has no connection to it's quality or the volume of additives required for cleaning. This flies in the face of those that think that bigger numbers (either in price or rating) must be better and the belief is backed up by marvellous marketing campaigns, but science is science.

Higher octane fuel simply resists detonation better than lower octane. That's it, nothing else. Whether your car needs high octane or not can be be determined very easily- what gas is recommended in your owner's handbook? It's that simple.

All modern cars can easily use up to 10% ethanol without issue. They were built for it from the factory. Again read your handbook.

 

Thanks all for your opinions and suggestions.
After considering it all, I may opt for what the car was built for and settle with the 95. I trust it will only be a few extra dollars but it may go a little longer and keep the engine up to good health, I think!

I'd have another enquiry and that would be:
Does the quality of the petrol varies between petrol stations and if it does, how do we know or quantify the difference?!.. .

Please note that I live in New Zealand and we don't have United or Independant (as far as I know).
We have: Shell, Total, BP, Caltex & Challenge

 

Different places have different gas.

If you don't have an owner's manual go to this thread and download it:

https://www.jaguarforums.com/forum/x...ownload-10577/

Here in the USA the sign outside the station is just a suggestion and the gas may come from a refinery other than the name on the pump.

 

Considering the compression ratio I wouldn't use less than 95.

2.5L 24-valve dohc SFI V6 [2.5]
Bore x stroke: 81.6x79.5mm
Compression ratio: 10.3 to 1 (91-octane unleaded)
Horsepower (SAE net): 192bhp@6800rpm
Torque (SAE net): 178lb-ft@3000rpm
Transmission: 5-speed manual (f.d. ratio 3.80:1)
Transmission (opt.): 5-speed manumatic (f.d. ratio 3.90:1)
Differential: center Torsen clutchpack
EPA fuel economy (city/hwy, 1985 test): 19/28mpg

 

Check with the manufacturer re the use of ethanol blend fuels. The reason for this is because some of the seals & plastics used in earlier engines & fuel systems react with ethanol, not because the engine cannot burn it. Mostly you will find that late 90's engine & fuel systems onward can cope.
Many yaers ago, probably too far back for most of the Forum members to recall, Caltex marketed a 'new' fuel blend which they called 'Boron'. It made a difference of up to around 2mpg (1.5 was common), primarily because we could advance the spark a little without 'pinking' (pre-detonation, pre-ignition, knocking are words more commonly used now). Higher octane fuels resist this, and computer control utilises 'knock' sensors to control the spark timing to minimise the problem. Higher compression engines usually require higher octane fuels to resist pre-detonation (which is basically when the compression ignites the fuel before the spark can). If you continuously run an engine that 'pinks', you will eventually (not overly long to wait, either) burn a hole in one or more pistons. As a rule of thumb, don't use a fuel with a lower octane rating than the manufacturer recommends so you can avoid this problem.
Some cars will give better fuel consumption on higher than recommended octane fuels, some won't. The only way to find out is to try by running the tank nearly empty, and refilling with the alternative that you wish to try. Ignore the first couple of tank fills, as they will be 'contaminated' by the previous fuel rating. Then keep a log & record your results. Whichever fuel then gives you the best 'bang for your buck' is the one to use. For some it will be an ethanol blend, for some premium, and others will find that the base fuel as recommended by the vehicle manufacturer will be the one to use. In my experience, that can vary between Marques, and even between models from a Marque. For example my Rangie gains nothing by paying for premium over standard, and an ethanol blend drops the performance & uses more fuel resulting in a higher cost per km ending up being about 5 t 6 cents a litre more expensive to use.

Cheers,

Languid

 

The evidence presented to support the conclusion disagrees with the conclusion.

Bear in mind that the EPA implies the US AKI octane rating method, so the poster may have allowed for the difference.

 

I follow the owners manual, its there for a reason, I expect the engineers who designed the engine designed it to use a particular octane rating, has to do with compression, and quite a few other factors, but mainly compression.
And as far as using the independant fuel companies, stay well away.Speaking from a professional viewpoint, I have worked in Scientific Analytical research and developement laboritories, hospitals and several years in the petro Chemical industry all round Australia, the large majority of fuel supplied by the independants just makes the goverment critera for fuel qualit.yI personaly would not use them in a lawn mower.
And by coincidence, to prove a point, a dear friend of mine used a local independant in the Point Cook area this weekend (in desperation the tank was really almost empty) and the car was hauled off to the Mazda dealer this morning with the engine management light on, and we have just heard from the technician with the comment, " thats the worst fuel he has ever seen in his life" drain and clean the two year old cars tank and start again.

 

the beagle is on the money. I also used to live in Pt Cook, and my next door neighbours had their Falcon Wagon breakdown coming back from Echuca. Clogged fuel lines, had been buying cheap (cheep cheep) fuel from an independant there. Likely the same one. That was seven years ago.
I'd be checking to find where Total & Challenge get their supplies from. Caltex, BP, & Shell would be from one of their own refineries (and they do 'share' between them - that same neighbour was a truckie, subsequently got a job driving delivery tankers for one of the three). The others may be buying on the 'spot' market in Asia & shipping directly to their own distribution point. Thus, as long as it meets the minimum standard, it's 'legal' to sell.

Cheers,

Languid

 

Gas from independents in most countries is usually not the best. And then there is the question of maintenance of the in ground storage tanks.

Another reason for keeping the tank comfortably above empty.

 

I have been sticking to BP 98 octane, and have not had any problems yet.
I've tried Gull and Z and found a lack in performance with their " higher octane " fuels. Car just seems to run and idle better on BP , lol and I don't work for them!
Having said that I have found adding a fuel system cleaner every 3 months is really good and works for me !

 

In NZ you really are best keeping away from Gul in my opinion. They tend to have the blend fuels and also don't buy the NZ made fuels.
We dont really have the small independent companies here, but even the smaller suppliers still have to comply with the same standards when it comes to storage tanks. So that's not a worry for us here.

I chirped up on an old thread because I Just happen to work at NZs only refinery and am also a tank inspector.

Cheers