A co-worker's wife had an '02 2.5 X-Type Sport and she used mid range 87. I have always used the 87 octane and the car seems to perform well. I have had my '03 2.5 T-Type for a year.

 

Actually, you are not saving anything by putting lower octane gasoline. Computer takes timing away and you find yourself pushing that pedal down harder by few percentages and you end up getting the same if not even worse gas mileage.

 

Of course the gas mileage does not improve and it's not supposed to by using a lower grade fuel. However, it doesn't decrease either if the accelerator is not abused. So, in the end you go the same distance on at least $0.20 per gallon. Herein, are the savings

 

Why does someone always want to second guess the engineers that designed these engines and any other engines that have 10.0 and over compression ratios. These engines require premium fuel to preform in the way they were designed. You gain nothing but eventual problems in the long run by using low grade fuel in them. What is there to prove by trying to save a few pennies at the pump. If you want to save these pennies so bad then buy a car with an engine that is designed to use regular or mid-grade fuel. I hear all these reasons that you can use lower octane fuel in these cars but when you look into it these make no sense. The computer is not there to correct preformace for using the wrong grade fuel no matter what some people think.
I just filled my tank yesterday with 16 gallons of premium. The difference between a tank of premium and regular would have been $1.60. If I can't afford that $1.60 then I shouldn't have bought an XK8. i use the factory recommended premium in my X-Type also for the same reason, because that's what they were designed to use.
BTW I use regular fuel in my 1964 Triumph Bonneville T120R for the simple reason, because that is what it was designed to use. I know of people that say they use mid-grade or premium grade because they get better preformance. that just isn't so. Here all they are doing is wasting their money. But since it's only a few pennies per tank full I guess it doesn't matter since it makes them feel better and it's not really doing any harm to the engine.

 

I was at a Sinclair gas sta. this weekend and they had 100 Octane fuel 'Racing fuel'. I might have bought it, but I didn't notice it until the guy had already started pumping my fuel, 91. I always pump my own gas, but I think they have an attendant do it exclusively. Weird, anyway, I am wondering if anyone has any info. on using 100 Octane in the X-Type.

Sam mentioned the fuel maps; if our cars are mapped for 91-93, then maybe they'll run poorly on 100 Octane. Also, I don't know how important brand is, but aren't the suppliers just a few big refineries in the middle East, and south American countries? ...and everyone refines crude to gasoline by the same methods. Therefore, who ever keeps the most water and moisture out of their gas is best.

Here are a few excerpts from:

performance - Racing Fuel (100 Octane Rating) - Better than Premium? - Motor Vehicle Maintenance & Repair Stack Exchange

The higher the octane, the less power per gram the gasoline contains. Use the lowest octane your car needs.

expanding on my answer: It's safe...ish to use on stock engines. The fuel burns cooler and may clog your catalytic converter. You certainly won't see any better power or mileage from it, unless you're tuned for 100 octane. It's sold solely for cars that are tuned for 100 octane: race cars and offroaders.

100 octane is usually leaded and will slowly kill both your O2 sensors and your catalytic converter. I believe I saw 100 octane unleaded at a track once, but I'm not sure how they managed it as my understanding is that 98 octane is the theoretical upper limit on what you can get without lead. – Brian Knoblauch

 

Octane rating has no effect on the burning temperature of the fuel. 'Racing' fuels of just about any octane are available in both leaded and unleaded, but all are an absolute waste of money in an engine that achieves peak performance on 91AKI/95RON.

 

Oh man, I've been using regular gas since I got my x-type, thinking the premium thing was all a marketing thing or a performance thing. I drove a while and things were fine but the other day I put in like half a tank of regular fuel and as I drove away my car felt like I put a ton of bricks in the trunk. The thing totally lost its power. At first I thought it might be like the weight of the extra gas, but it was clearly the gas I used. Must have been a bad batch. I also heard a clunk sound today too when I had the hood up and started it up. Definitely will only be putting in mid-grade or premium from now on.

 

In Ft. Lauderdale, there is a VP fuels (racing gas) station. They sell C9 fuel, 96 octane, unleaded, race and storage fuel, right from the pump. It's wonderful stuff. Zero ethanol, properly refined, for all practical purposes never goes bad, and without going into tons of detail, it atomizes very evenly (something modern fuels have some issues with) . Lets put it this way, it's very high quality gasoline and it shows.

I recently tried it in my X-Type, 2.5L manual, on a whim. It helped! The car was significantly more responsive, accelerated faster, and was smoother.

But, you also must remember, that here in South Florida, it's HOT. Octane requirements go up on hot days. Timing gets pulled by the knock sensor more often on hot days. On a cold day, there may be no gain at all. I don't know.

In any case, my 2.5L engine accelerates unevenly on 87, likely due to the knock sensor pulling timing. It's annoying. No such issues on 93.

And, yes, 96 octane has, for years, been the practical maximum for non oxygenated unleaded. The addition of large quantities of Ethanol bring the octane up to over 100. Or MTBE. Neither mixture is likely to have any positive results on the X-Type.

 

I wish I could get that high of octane here in Oklahoma..Although we have many stations with 100% gas, but no higher than 91 octane..

 

Remember guys, its not just the octane rating but also the quality of gas. There's a very good post on the x308 forum somewhere that discusses advantages of buying brand gasoline (chevron, shell, etc) vs. non branded at indie locations. The additives do work to keep your fuel system clean. I switched to chevron or Mobil premium for my Alfas (always ran premium in the XJR and my bikes) even though it maybe an overkill for older engines. My wife's leased e90 still gets regular though. I just don't have that love for leased cars, don't know why...

 

Like most Jags, the engine in an X-type achieves full potential on 91 octane, in other words there's no detonation and full timing advance.

Using higher octane fuel achieves nothing despite what a persons butt dyno tells them.

The octane rating of a fuel has nothing to do with 'quality' or level of additives. There's more myths on this subject than almost any other.

 

Amen!!!!!

 

I burn 91 octane (V-Power) Shell in the Jag..and Conoco 89 octane (cuz it's tuned for 89) in my Hummer.

I never use no-name gas like, 7-11

And I never, never, ever burn any Ethanol moonshine..I'd walk before I would use any of that crap.

 

I would be very surprised if you hadn't unknowingly been using it. E10 is nothing new, most of North America has had it for 20-30 years. The only thing 'new' about it is the pump labelling.

We've had it here for 20+ years, never had a moments problem nor do I know anybody who has. Yes, I know all about boats, weedwackers etc etc.

 

Stopped by the station today and put in a few gallons of premium to top off the regular gas I had put in earlier in the week. Noticed a big improvement right away. The car feels nearly back up to it's full potential, the power is back and the engine is not making a rattling sound anymore when I accelerate. Definitely will be sticking with premium or mid-grade at a minimum from now on.

 

Hey Mikey..SURPRISE!!!

Yes, hard to believe, but we in the USA do know how to read and know what Ethanol E10, E85 is and we've even learned that it smells like booze too....But just to be sure that we don't get it mixed up..The stations here post BIG signs that read: "100% Gasoline, NO Ethanol"...and if that isn't enough, for us really stupid people, they put stickers all over the pumps that say the same thing...

What is it with you friggin Canadians? That you always come across like you're smarter than everyone else, or at least the US people..Frankly I'm sick and tired of you Canadians and your condescending implications toward us in the US on these boards.


If I get banned for sticking up against what is plain insulting, then I don't want to be a part of these boards anymore ...So Jim go ahead and pull the trigger, I'm sick and tired of these insults from these people.

 

Here in the US - that's the country with 300 million people mostly to the south of Canada - we have a lot of regional variation despite our national government trying to force us into mindless compliance to a central authority. One of those regional variations is the availability of 100% gasoline (I can't get it here in Chicagoland, though). If I could, though, I'd search it out for the additional energy content it has. By my calculations, you lose about 3% of available energy with the standard gas/ethanol combo. Sure someone has covered it, but ethanol is higher octane but lower energy.

 

In regards to what Canadians say, I think that it is more if a cultural thing. I have had a opportunity to go to different places in the world and the way people, perceive, interact with and treat Americans is, well, interesting to say the least. Typically they mean no harm, but I do understand how it can be very irritating if not taken within the right context.


As far as gas is concerned, I use the highest grade available on the 74 E type, the 95 XJS and the X. Here in Houston every single gas station has the infamous Ethanol warning. I do not know where I could go to get ethanol-free gas. Knock on wood no probs

 

Canada, and Canadians aside, I have owned several automobiles whose manufacturers indicated "premium gas only". I could never think of any ulterior motive for them to do so. Most of them also manufacture power plants for which they recommend lower octane fuels. Therefore, it's never crossed my mind to attempt using any fuel other than that which I have been directed to use. With the X-Type I knew I was required to use "premium" going in. And so, I do.

 

Wow............no offence intended.

The right context was that E10 is nothing new, but pump labelling is.

Ethanol Labeling Laws - State by State Guide.

Many states and provinces still do not require labelling- but that doesn't mean that the fuel is NOT E10.

Not everybody is/was aware of that on both sides of the border.

No need for an international incident