If I recall correctly the middle grade at Exxon is 89octane and I used it for years in both my xk8 & 3.0 S-Type without any noticeable problems. I cannot tell you when I purchased premium octane. Just my .02¢

 

I agree with the suggestions of cost: the difference isn't insurmountable. Additionally, if you don't care about performance, you could always sell it, buy a cheap beater for around town, and pocket enough cash to fuel that car for a solid year.

 

No flaming needed- you're pretty much spot on and thank you for the compliment.

The failure of your catalytic perverter would not have been due to presence of the ethanol in E10 or lower octane levels. For all it's other failings E10 is actually kinder and gentler fuel on cats than gasoline. I can only presume that your difficulties were just a coinkydink. All my cars and other toys have had a steady diet of E10 since day one with no problems.

On another favourite topic- there is no correlation between octane levels and 'quality' of fuels. Given that the vast majority of vehicles here run on regular (87ish) octane gas, and that there's no real relevant mechanical differences between a low perf motor and a high perf., why don't the low perf cars suffer from issues if the 'quality' of the fuel was inadequate?

As a classic example- remember that the fuel injectors are OUTSIDE of the combustion chambers and upstream of the intake valves. They have no idea what's going on downstream, and couldn't care less. Why do they not clog on low perf cars using 87 octane fuel, but supposedly would on a high perf. car when fueled with the same 87 octane 'low quality fuel'?

 

Jeff,

I tried running the Sunoco 93 octane ultra a couple of times just to see if I noticed any difference in performance or economy. I didn't notice any difference in performance. When I tried measuring economy, it seemed everytime I tried it, there was an accident or other snarl in my commute route. I couldn't get a good reading. Switching back to the mid-grade didn't seem to improve the accident rate though.

 

Deep breath, final thoughts:

All gasolines are NOT equal, octane is what really sets them apart.
Octane measures the ability of a fuel to resist detonation (knock).
Excessive detonation may eventually create the conditions for pre-ignition.
Detonation can cause long-term damage, pre-ignition can kill an engine in seconds.
When the ECU detects knock and adjusts the timing to avoid damage, there is a loss of efficiency and mileage.

Not a good idea to use gas with a lower octane than Jaguar recommends.

Not necessarily fatal either - if you drive the car like Miss Daisy you might even be able to get away with kerosene.

..and be careful with methanol – it is corrosive and should not exceed 3% (Jaguar manual).

I'm off to tickle an otter…

 

So what is the minimum octane that is acceptable in your opinion?

 

My Jag manual says "at least 95 RON, up to 98 RON", implying an AKI of about 91 - 94. That's for a supercharged engine.

Could go less if the car is not driven hard.
Never hurts to go higher, except at the Bank.

Now where's that otter...

 

Not to hijack the thread away from the octane wars (heard Costco was best for AZ), but $5.00 a gallon gas equals US recession. Without writing a novel, everything you own is transported to you, therefore your commute is not the only thing that goes up ~ everything you pay for will increase. So $5.00 a gallon gas for the US will make for a very interesting world.

 

lol!

 

You can always sell it to me ...

 

Different Octane Rating systems. Compare online. Regular in the US is over the reccomended 91 ROM in Europe.

 

While a true statement. The US owners manual states the recomended fuel is a minimum of 91 AKI not RON...

 

True. And minimum here in the handbook is 95RON.

 

Since the cost difference for regular versus premium is usually no more than 30 cents, the answer is no. It amounts to maybe two dollars a tank. Big deal. At $3-5 per gallon, the difference far less than 10 percent.

 

Just "fixed" (I hope, so far so good) the "engine fault/dsc not available/parkbrake" condition which seemed to come up a couple of weeks after I switched from Premium to Regular gasoline. I'm doing a complete 180 on this and sticking with the Premium.

 

Don't hate me for taking a slightly different stance. I work for a company that services the oil & gas industry. The more fuel sold, the more created, the higher the prices go, it's all good for our sales. The more demand and higher prices just seem to increase our sales of support equipment. I pay whateve crazy price necessary for premium fuel and embrace it as job security. i suppose I'm part or the problem and not the solution.

 

I dream of petrol at $5 a gallon
Oz prices: 98 octane $1.60 per litre or $7.27 per gallon!
middle octane 95 ron $1.40 per litre or $6.36 per gallon!
and these are the discounted prices, just take a breather and be thankful for small mercy's.

 

I always get a kick out of these statements.. Now I'm not trying to pick a fight, but remember, a particular country's price structure for gasoline is based on many other factors other than wholesale price. See, everyone "pays" the same basic wholesale price (granted there are also the complicated issues regarding currency exchange) the great price disparity comes into play when governmental taxes come into play. I'm just saying, don't hate on the US just because we don't have huge fuel taxes. Again, I'm not trying start political debate, please.. I just felt the need to clear up what I see as a misconception.

Here are prices around the world... this is an old graph, not today's numbers




And here is a graph showing taxes on gasoline around the world (notice the US is on the bottom). Again, this is from a while back...



OK, I know the graphs I put up from the internet are a little dated... I wasn't looking for current accuracy, but more something to illustrate the situation.

 

You see our taxes.... and still we run a deficit (*)

(*) deficit = annually the government spends more than it gets, they're now trying to reduce the annual deficit though not to a surplus!
result: roughly a trillion GBP (that's over $1.5 trillion) national debt

 

So you're saying that low octane gas caused a dsc and park brake fault? I see no connection, sorry.