New X-Type owner. 2.4=5 model. What gas should I be using?

 

You need to use 95 RON Fuel (Premium Unleaded)

If you look inside the Fuel Door - there is a label to remind you

 

93 Octane here in the US (premium unleaded) - I believe Jag specifically states at least 91 Octane...

 

I always use 93 or better.
It burns at a higer temperature=more power, less gunk left behind because it's higher quality fuel. Better for the engine long term. Even though its more expensive, take it from someone who replaced their engine for 4,000. Paying the extra 40 cents a gallon is worth it.

~Fury

 

Might want to read how different RON ratings affect engines.
Higher RON number does NOT increase power.

The fuel still contains the same calorific value.



Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.
However, burning fuel with a lower octane rating than that for which the engine is designed often results in a reduction of power output and efficiency. Many modern engines are equipped with a knock sensor (a small piezoelectric microphone), which sends a signal to the engine control unit, which in turn retards the ignition timing when detonation is detected. Retarding the ignition timing reduces the tendency of the fuel-air mixture to detonate, but also reduces power output and fuel efficiency. Because of this, under conditions of high load and high temperature, a given engine may have a more consistent power output with a higher octane fuel, as such fuels are less prone to detonation. Some modern high performance engines are actually optimized for higher than pump premium (93 AKI in the US). The 2001 - 2007 BMW M3 with the S54 engine is one such car. Car and Driver magazine tested a car using a dynamometer, and found that the power output increased as the AKI was increased up to approximately 96 AKI.


More info here

Octane rating - Wikipedia, the free encyclopedia

HTH

 

Very nice explination, I was partially right.
Qucik question, I don't know if you've heard of Joe's Ford GT"TT" he runs on race fuel, which I've heard is anywhere from 100 to 110 octane.
Are you saying that if I used race fuel in my Jag it would or wouldnt produce more power?
I know in the video the twin turboed GT puts out 1500BHP but on a more normal octane it would produce 1100-1200 same goes for the twin turboed lamborghini aventador that's rated at 1700-1800 BHP.

Enlighten me please.

Also, I this is for everone else, when getting a car check the owner's manual to see what the reccomended fuel type is.
My father always used 93 octane, even in our 2000 ford excursion, turns out the reccomended octane was 83. Turns out that due to the higher octane he could have blown the pistons right off, and thus he lowered the octane to the reccomended level.
My mother's 2007 Lexus ES350 requires 87 octane. So it is different for every vehicle.

~Fury

 

Depends on what race fuel is used.
If it has a higher calorific value, then yes it is possible it would produce more power.

Basically, the higher the RON, the more the engine can burn the fuel before it self ignites and causes detonation/pinking etc.

The management systems change the timing of the spark to avoid this detonation which in turn reduces the efficiency and hence the power of the engine.

 

Boss, like what tanis is getting at, by running higher octane gas, the octane is retarding when the fuel can spontaneously combust (due to rapid pressure changes). A higher compression engine will have much wider pressure swings (and therefore more rapid pressure changes) during operation. A higher compression engine pushes all the air/gas together closer, therefore the flame doesn't have to cover as much volume to burn all the fuel, therefore burning more of the fuel in the cylinder. More fuel burnt in the cylinder means more power. Also the higher octane fuels allow you to start the spark a little sooner, giving you more time with the fuel burning inside the cylinder, again, netting more power output.

 

All gasoline contains the same calorific value, it all burns at the same speed and at the same temperature. The ONLY difference that the octane rating makes is the ability to resist detonation.

If an engine can operate at optimum ignition advance without inducing detonation, using fuel with higher octane will achieve nothing except lightening the owners wallet.

Octane rating is also NOT a measure of 'quality' or the amount of detergent additives it may contain.

Fury-

Your father's Excursion would not have been damaged by using higher octane gas.

 

There's a small airport near my place. Occasionally, I'll stop by and fill up with 97 Octane, airplane fuel. It costs about 1.3X more than 87, but man, it sure puts extra power into the engine.

 

I never heard of 97 octane avgas. I know of 100LL (low lead) which has MORE lead than the old automotive leaded fuel. I'm surprised you haven't had catalytic converter problems if that's what you're using.

The fact remains, the ECM is pre-programmed with timing data. It usually has a high octane map and a low octane map. If detonation is detected it simply retards the timing by using the low map. But it cannot advance the timing beyond the high map no matter how good the fuel. At some point in the future the ECM tries the high map again to see if it can deliver better performance without knock (checks to see if you added better fuel).

That's not to say a better grade gas can't clean a system and deliver better performance but it's no better than what was possible when the car drove out of the showroom.

 

I had to laugh. Many moons ago I worked as a flight instructor at the small Aero Club at USAF Lakenheath, on the east coast of England. I had an old Cortina which one night we filled up with 100LL. It ran ok, but never ran well afterwards!
Ended up scrapping the car when the engine gave out.

 

I agree which brings the point of the original post. Do you really need to shell out for the higher octane?

How many on here run 87 in their car and don't have issues?

 

I actually get better mileage out of 87 but I alternate grades to help keep the engine clean. But I'm easy on the throttle. If I was going to put my foot down I'd stick with 93 to protect the engine.

As for the Vette, I reprogrammed the octane maps for max timing advance using only 93 octane with a little safety margin. No low octane ever touches the tank.

The bottom line is, you can drive any street car on 87 if you keep your foot out of it. The harder you push the car, the more timing advance it tries to run. Manufacturers made sure you could get home on whatever is available but the engine won't be as responsive. It all depends on what you want out of the car. If you ever hear the engine pinging, get off the throttle and get high octane in it as soon as possible.