Upgrade fuel for XK

[DOROTHY]

Hi, Does anyone know if top grade fuel can alter the gearchange on a 2006 XK?. It may sound silly, but I have always used 95 octane from my local supermarket in my XK non supercharged model. After reading the article in this months JEC magazine regarding E10 fuel, I decided to fill up with Shell V Power. The car certainly runs smoother and quicker and I will be using this fuel in future. However, it may be my imagination, but she seems to change down on upgrades more so than before. This does give more acceleration on hills than I am used to, although frankly, it is not needed. So my question is, does the engine recognise the upgrade in fuel and change the way the gearbox responds, or is it my imagination?
Any ideas?
Rob

[mike020150]

As pointed out in the magazine article, any changes in performance can only be very small. By moving to a higher octane fuel, that small increase in power (torque) should have an equally small tendency to reduce the number of gearchanges. So, the chances are that having made the move in octane rating, you are taking more notice now of what the gearbox is doing which is probably the same as before! Mike.

[DOROTHY]

Thanks Mike,
I suppose I am being a little paranoid after having the gearbox Oil and filter filter changed for the second time. I broke the plastic sump on a sleeping policeman before I changed to the new fuel, so I was worried I had damaged the gearbox itself. My people checked the box electronically when they changed the oil etc, so all should be well there, so I was just looking for answers. It just seemed a coincidence for the box to feel different.
Thanks again
Rob

[3.8etypephil]

Thanks Mike,
I suppose I am being a little paranoid after having the gearbox Oil and filter filter changed for the second time. I broke the plastic sump on a sleeping policeman before I changed to the new fuel, so I was worried I had damaged the gearbox itself. My people checked the box electronically when they changed the oil etc, so all should be well there, so I was just looking for answers. It just seemed a coincidence for the box to feel different.
Thanks again
Rob

If they reflashed the gearbox after the oil change, that would explain the improved responsiveness.

[DOROTHY]

Thanks Phil.

[ng4xjs]

I know this is an older post but thought I would share my recent (October 2023) experiences with fuel and grades during our road trip to the Algarve (to visit my Wife's Niece and wider road trip). I generally use E5 98 fuel in my X150 (I know the E10 is fine. As have done also for my XJS for many years).

France is good, with a plentiful supply of E5 on our route down and with mostly automated pumps made for easy and quick fill-ups. Spain reasonable but on occasions opted or the E5 95 if the 98 was not an option. Again our experience was good with a few service stations having pump attendants. Portugal was more difficult and I don't recall any E5 98, mostly E5 95 and E10 95. The slightly more difficult aspect in Portugal is the (as I understand it) legal requirement to pre-pay for your fuel. Just makes it more of a guess if trying to fill the tank. What I would say was that over the 3700 miles we travelled, and for our relaxed driving there was no appreciative difference in performance. We also averaged 31mpg, not bad.

And although we did take advantage of may toll roads during our trip it has to be said what a pleasure driving Portuguese, Spanish and French Roads.

Happy days
Nick