When I recently bought my 2001 XK8 "Project", the PO told me that he only used regular (87 oct) gas! So naturally, I did the same. Now after spending some time on this forum, I see that the proper care and feeding of these cars requrires the good stuff!. I will amend my ways immediately!. Could the extended use by the PO of the low octane stuff be one of the reasons I get the "Restricted Performance" DIC message occasionally?? Is the 2001 4.0 ltr engine hardened against the ravages of E10 or should I be regularly pouring E10 treatment into the tank in addition to premium gas?

Thanks

 

One of the former members lived in the GA mountains and used 87 in his 2002 without trouble. Check for knock sensor errors when the restricted performance is on. I tried 89 octane for a while to see if it affected mileage and saw no difference, but my personal opinion is that if you can't afford premium, sell the Jag and buy a Prius.

These engines are designed to run on 10% ethanol, so don't worry about that.

 

Thanks, RJ237. My post wasn't about affordability but rather what the Jag needed. Rather than buy a Prius, I would prefer to sit down and eat my XK8 one bolt at a time.

 

I know it wasn't a cost issue, just making a joke.

 

It never ceases to amaze me how some people WOULD skimp on buying the correct products for their toys. When I was on the Hatteras forum, there were members there that had 50 to 60' motor yachts and lost sleep if they couldn't haul diesel fuel from a street service station in 20 jerry cans rather than use the correct marine grade fuel at a marina.

 

I have a question about rear ends (preferably posi) and around 3:73 gear ratio. Any thoughts or leads?

 

My efforts to stop the overheating problem have hit a snag....seems the accelerator in the XK has changed position some way when I set the intake up on the cowl (accelerator was never touched)...any idea what might be going on...damned hard to get to that accelerator!

 

If the knock control system does its job there’s no harm to be done and the sound of knock is unmistakeable. RP mode is often an intermittent throttle problem, read the pending codes.

On my 6cyl I run exclusively 87 where performance maxes at 90 (95 RON) octane fuel unless you do some tricks. Maybe the V8 is less conservative and can take advantage of 93 but who knows. If you value the performance of your NA car (i don’t) then putting premium is the obvious choice.

Running regular on the boosted cars is of course just dumb, my 4.0 SC gets the cheapest premium, usually Sam’s Club or Costco.

 

I used 87 octane of any brand in my car for years with no problems. I bought it in 2005 with 18,000 miles. It now has about 103,000 miles. The only fuel system problem I ever had was a failed fuel pump. I would occasionally put some fuel system treatment or fuel injector cleaner in the gas. Now that I don't drive the car much, it's only name brand premium, the best stuff available. The cost difference is minimal because of the amount of gas I buy for the Jag.
So, if you're having issues, I wouldn't just assume it's because of the gas used by the previous owner. I'm not saying it's not possible, but don't assume.

 

No real isues to speak of excepting the occasional RP DIC message whcih clears up after a while. I just want to be sure the XK8 is getting the gas grade it was designed for. Thanks all.

 

If you are getting these RP messages, you should read the accompanying trouble codes and go from there. Usually, these type of errors can be read with a generic OBDII reader. Get a cheap ELM327 (eBay, Amazon) and a mobile app if you don't have a code reader yet.

Best of luck, keep us posted.

 

Actually, I do have the code reader and (going from memory right now) the codes were very similar to what other members were getting for RP; In general they were translated into "miss-fire cyl n," with 3 or 4 cylinders being listed. also, Evap leak detected (small leak). When I get back home this weekend I can post the axact codes. Thanks