It simply says 91 is recommended for best performance, it doesn't mention any potential negative consequences. I've never put anything other than 93 octane in the Jag, but my wife occasionally has put in 87 octane in her MDX and says she notices zero difference. I would love to Dyno data on the performance difference between 87 and 91 octane.

 

Is it possible that maybe her driving style would not reveal any difference? Simply because it's not obvious at conservative driving moods..Not Saying your Wife is not perceptive, just that it could also be that she filled a tank already half full of 93 octane, where the mixture was still viable enough to maintain the performance she was use to..A lot of variables to consider.

And of course I mean absolutely no disrespect towards your wife's driving skills or abilities to know normal behavior of the car..

 

This echos many other owners' experience from what I can gather.

 

Most don't notice, whether there was a change or not. They drive from A to B and notice nothing.

That provides no data as to whether there was any difference.

 

Very true. This is the opposite end of the scale from those who claim to see vast differences from making insignificant changes. The 'butt dyno' placebo effect.

 

I totally agree with what you are saying. That's why my other question was if anyone has any hard data to back their hypothesis one way or the other. It's not a huge deal of course, just curious more than anything.

 

That my friend is the million dollar question...

I will be the first to admit that I don't know for sure with black and white dyno-data, of how much of the performance is depreciated by using lower octane fuels other than what the manufacturer recommends...I have hard cold facts that using E10 fuel will degrade mileage by much more than 3% though... Nor have I seen data here from any of the know-it-alls to the contrary if any performance is negated or not...I just know and willing to admit that I am not smarter than the engine's maker to say that it makes no difference, or the labeling and info in the OM would say just that...To say anything different, would be bold and arrogant and the height of ignorance.

I get that circumstances may leave one with no options and have to pump in lower octane, but those situations would be rare and few. The Jaguar manufacturer obviously considered this to be a condition you could get by with for short periods..so fill up ASAP with the recommended fuel octane level.

 

Here we go again. You say this- but make statements (as thought they were fact) that the car will make more power with higher than recommended octane,on top of dire predictions of what would happen if lower than 91 fuel is used. All assumption and speculation, nothing based on fact.


Your experience seems to focus at least partially around a lawnmower which you presume translates to what might happen with your Jag. This is in spite of simple logic that casts doubt over claims that E10 reduces mileage more than 3%.

On the other hand, I have extensive experience switching back and forth from E10 to 'pure' fuel on mine and saw no change in mileage or performance attributable to the fuel. You apparently reject these 'cold hard facts' for unknown reason.


Jaguar makes no mention of usage only for short periods. Why put words in their mouth? Do you have any 'cold hard facts' to suggest it is for only temporary use?

To quote:

"To say anything different, would be bold and arrogant and the height of ignorance."

 

I don't understand that when an engineer or manufacturer who makes and designs a particular vehicle is questioned by a driver that has bought the car and wants to avoid all the particulars of how that vehicle is run. I ran vehicle emission tests for years and yes, fuel can alter the emissions as does the wrong oil. Check with your local inspector and it can be verified. Don't want to pay the fuel price for such a nice performing vehicle, buy a Toyota, Honda or something like that. Quit trying to find facts without understanding the cars geometrical design and performance qualities. Ask a race driver, they can answer these questions with facts. Wow, I want cheap fuel, I want performance, I want. Get over it.

 

Hello Pot meet Kettle...Never said that...you are the only one that did..Now Who's put words in mouths?


Key word is partially and not around or totally based on a lawnmower..get a life.. ONLY as just one more example of how mileage (and that term is relevant to engine run time) compared to NON-Ehtanoil fuel....You failed to remember the most important example of about 5 or 6 different fill ups comparisons I did before I realized ethanoil was a waste of money in an Engine managed system that repeatably suffered about 8-10% unlike your fairy-tale 3%.

Because, I know BS when I see it.. Especially when people use words like extensive ...


Nor does it say anywhere you can continually use 87 octane...An average intelligent person can Read between the lines.


To pretend to be smarter that the car maker, would be bold and arrogant and the height of ignorance.

 

OK, so exactly what did you mean then:

The car is certified to produce full rated power on 91AKI.

I disagree with the notion that it was inappropriate to ask this specific question or anything similar. That's half the purpose of having discussion boards. The OP's motives for asking are irrelevant and there's no requirement to justify posting any query.

On the other hand, if there is a downside to the view point that 'there's no stupid questions' is the possibility of getting answers that are incorrect, misinformed or just plain malicious which defeats the purpose of asking.

In this particular case, the OP asked a common 'what if' question. The answer to that question is contained in the owner's manual. In my mind, their position is quite clear stated. Case closed? Ummm, no.

Amazingly, some responders choose on an ongoing manner to ignore the OEM's written position and inject all sorts of myths, assumptions and speculation, none of which is backed up with any sort of substantiation or proof.

I'm not quite sure what 'asking a race driver' would accomplish. They might be well skilled at getting the car around the track quickly, but that does not depend in the least on them knowing how an engine works. There is the further point that what's required or works best for a racing car has little relevance to a mid size luxury sedan used as a grocery getter.

There's always the option of skipping over posts if the content is too upsetting.

 

What a completely unnecessary and condescending post. Questioning the reason behind recommendations and wanting to understand whether they are performance, marketing, or CYA driven seems perfectly reasonable to me. Engineers and manufacturers sometimes get it wrong, hence the thousands of recalls issued every year by the auto makers, and thousands of lawsuits settled. I guess if you enjoy being a sheep and never questioning anything than these types of simple questions would offend your simple mind. By the way WTF would geometrical design have to do with anything discussed in this thread?

 

True..I have yet to see anyone argue this.

The range of the octane tables are more than likely skewed to favor the Higher side or above 91 octane and so what I exactly mean is, I want to be well into that range with 93 and not on the bottom edge of it at 91 for optimum performance under all positions of the throttle.

As I've said before, to each their own on how they rationalize their excuses for using the type of Octane level and/or fuel in their own car...I myself will not compromise...

 

SOMEONE PLEASE, FOR THE LOVE OF GOD, TELL ME ===WHY=== THEY WANT TO RUN 87 OCTANE IN THEIR TANK.

I'm sick of the argument as to whether you CAN or not, and quite frankly I think it's irrelevant.

What's bothering me is why on earth anyone would WANT to. To save 20cents/gallon? It boggles the mind that there are people who will spend huge amounts of money on cars like ours and then seek to save every cent they can when putting gas in it.

Unless the people so passionately arguing against the need for premium fuel are willing to answer that question, this thread is entirely pointless.

 

Well said Dave..

 

If there's something 'pointless', it's commenting on what type of question posters can/cannot ask, even moreso when it's the third or fourth time it's been commented upon.

 

Nobody is forcing you to read the comments. If you are sick of the discussion, move on to something you think is relevant!



Why do some people wait until tires are totally worn out before replacing them and others replace when they're only half worn?

Why do some people do routine servicing twice as often as recommended in the manual?

Why do some people check their fuel economy at every fill-up and others never bother at all?

Why do some people insist on a certain wax, or car wash shampoo, or tire dressing?

Why this, why that, why anything?

We all have different hot buttons, different things that we're particularly concerned about even if they really are not very important in the grand scheme of things and are not important to most others.



No, what is entirely pointless is that you would demand an answer as to WHY something is important to another person.

If you think the discussion is pointless, move on. Nobody here is under any obligation to prove to YOU that a particular conversation or concern is important or relevant.

Get over yourself already




Cheers
DD

 

I drive my 09 hard whether im going to the store or on the highway, pretty much everytime it hits the pavement itll see full throttle. Cant say ive ever felt any difference in the performance of the car from different gas octane. I ran 87 for a while and have since switched over to 91, switching back and forth every once in awhile there is no difference. if you feel there is a difference its placebo effect. run what you want...simple

 

Jacob,

Thanks for posting. This adds yet another data point to an obviously controversial subject.

If I remember correctly, you have the supercharged version?

 

Yes I have the supercharged model....ive had many sports cars over the years, always tried high octane fuel, some would respond to it others theres just no difference. WISH it made a difference, damn that would be an awesome and cheap horsepower boost but it doesnt in my jag....Now when I was riding street bikes and used to get the 108 octane from one of my local gas stations, THAT was nice, this was back in 2002-2008 think that stuff was like $8 a gallon towards the later years. Good times!

Remember where on the internet, who cares! ...give your experience and let the OP decide....Happy new years