I live in California, where the highest octane fuel is 91. Would my 2005 XKR run better on 93 octane and, if so, would it be advisable to use an "octane boosting" fuel additive to increase to 93? I also note that many of the fuel additives that purport to boost octane are designated "not street legal"...

 

Jaguar vehicles have different specifications across the World markets. Some of the differences are to ensure they will operate safely and satisfactorily on locally available fuel. The recommendation in the US Driver's Handbook is "use only premium unleaded gasoline with a minimum anti-knock index (AKI) of 91".

Jaguar also do not recommend the use of either fuel or oil additives.

Graham

 

91 works very well. Even if you had 93 in your area, the car would not run better on it. So no, no octane boosters needed or advised. The ones that actually do something (on a very minor scale) WILL also put a reddish residue on your spark plugs and on the combustion chamber, valve heads, etc.

Z

PS ......FWIW, the only fuel additive that I know actually has some cleaning power is Chevron's Techron Fuel System. Jaguar may not recommend it, but it will dissolve some fuel deposits. Deposits which could impede fuel system efficiency. I've never heard of any verifiable report that using it had any negative aspect, aside from hurting your wallet.

 

If you have a properly maintained car running all stock component, best is to follow Jaguar's spec (I believe it is printed on the inside of the gas cap cover, and it specifies 91). Now if your car is not up to par (say, the intercooler pump is not working, or a plugged cat) and the intake air temp is higher, or if you have after market pulleys designed for more boost, then higher octane may help. Listen for octane issues. Best is high load, low rpm and check if you hear signs the fuel is not up to par. You might also want to check the ignition timing (over OBDII) and see if you have signs the knock sensors are detecting problems. That being said, I have no direct experience with additives to boost octane rating, if they can be trusted or even are compatible with the specifics of the Jaguar engine/fuel system. I would not use them personally. Gas stations around here offer 93, and 91 is a bit rare (Sunoco does, I think). Maybe if you look around, some stations carry 93. Just beware of any type of high octane race fuels as these might have lead and will ruin your cats.

 

I pretty much agree with all previously stated above. I sometimes wonder if any difference I "feel" with an octane booster is just placeboo effect. IMO they are not worth it.

OTOH if you have some spare $$$ and want to see something fun, but 10 gallons of Sunoco unleaded racing fuel. It's 107 or 110 octane, pure gasoline zero alcohol.

I bought it on line once, they deliver it to your house in 5 gallon cans. It's expensive, 10 gallons cost at least $200, but I don't regret treating myself to it.

I ran the gas level way down near empty than added the 10 gallons.
The "sound" of the engine was different, I sure did feel a bit more power, funny or unexpectedly gas mileage increased!

I suspect that most of the improvement was lack of alcohol additives, but like I said I'm glad I tried it.

with that fun memory on mind I decided to hunt around to see if any one sold this at the pump. Found a station over in Pennsylvania and when I had some cash, drove over. Whew, it was a WOT. Either they just never moved the expensive racing fuel and it was old or it was mislabeled. Absolutely no improvement , in fact I wondered if it clogged the feul filter.

If you ever decide to try it out, I recommend just buying it on line directly from Sunoco.

have fun, John

 

BEWARE of that racing fuel, some achieves that higher octane with the addition of lead, like in the old days. Besides being a neuro-toxic and generally nasty, lead also destroys catalytic converters. The flap on the gas cap says "UNLEADED".

 

wwwRayR,

If you want to increase your Octane to about 111, you can Install a Snow Performance Boost Cooler. I installed the Stage 2.5 Boost Cooler several years ago and it squirts 50% Methanol/50%Purified Water into the Throttle-Body whenever the Boost Gauge gets up to about 8lbs. and then continues on up until you let up on it.....All this for somewhere around $550.00 or $600.00. Then you won't have to worry about 91 Octane anymore...………..Go to...….www.Snowperformance.com
Have Fun!

Billy Clyde in Houston

 

Thanks for the info on Snow Performance -- very intriguing! I doubt that such systems are "street legal" in California, however. BTW, the correct URL is www.snowperformance.net.

 

I have been using Sunoco Ultra 93 since I bought the car. So far I have never noticed any problems. The car runs very smooth and quiet. I never tried 91 in it.

In October I'll run it to half, dump in some Star Tron and Stabil, go out for a drive then the car sits until April or May.

 

Hey Ray! I really thank you for showing me how to get into the Snow Performance Web Site! I have it stored in my favorites and never have to actually spelling it out....I just click on it! As far as the System being "Street Legal" in California, I wouldn't bet on it but they do have numerous Shops out there that Sale and Install them! Go to www.snowperformance.net and check them out. I started using the Boost Cooler a number of years ago when I got my 2000 XKR, then installed another on my 2003 XKR and have had my current one since I bought the 2005 XKR. They work great with XKR's, as it cools the load before it goes into the S/C which forces the Methanol/Water mix into the combustion chamber along with the cooled outside air! the Website brags that it increases the load up to 117 Octane....That's getting into aviation fuel "High Octane" performance....The XKR runs around town on 92 Octane until the boost gets up to 9 lbs....Then is starts progressively squiring the Mixture into the Throttle Body and off you go!!!! Works every time and if you want to, you can pour in a Bottle of "Nitro Boost" and get an extra "Kick" that way...….

The only problem is that about once month or so, I have to go.to the Hot Rod Shop and buy a couple gallons of Methanol to mix with purified Water...That cost about $11.00....I can tell the difference or I wouldn't continue with it....To make it easier, I use the Windshield Washer bottle for my M/W supply.....BMW has started using a Water Injector on one of their new M Series Cars just this year......It Works for them and it Works for me!

Billy Clyde

 

I use 99 ron shell v power most of the time,works out around £4 extra a tank full against the standard unleaded in these parts of the UK, plus it's very handy only living 100 yards away from the shell garage lol👍personally I feel the car always runs that bit better overall