I did something very stupid just because the sign on the gas tank door says 91+up gas so...Why they didn't make that sign more specific saying PLEASE don't add racing fuel to the gas tank.But anyway what happened was I started putting racing gas in my gas tank every now and then and you know what it did?it DESTROYED my catalytic converters!When that happened,the engine refused to have any power,stay running,misfiring, and everything.I was lucky to get in the shop in time and they were able to fix my XKR with an emissions warranty before it runs out in October.Long story short,dont ever put racing fuel in your gas tank or else it will be hell to pay

 

Yes, racing fuel can have lead as an octane booster.

 

If you use leaded racing fuel in any vehicle with catalytic convertors it will destroy them,
has been that way since catalytics were first introduced 45 years ago.
They make unleaded racing fuel that will not harm anything however
unless you custom tune your car to take advantage of the extra octane you
will get zero increase in power,,it may actually make less since higher octane
fuel is harder to burn.
If you can run a custom tune for the race fuel then you can make extra power,
in my previous supercharged Mustang I made 33hp extra at the wheels on the dyno with a race tune for 109octane unleaded
compared to the 93 octane street tune. With an external tuner it is relatively simple to switch back and forth,as far as I know no
such tuner exists for the Jaguar.

 

it will give you a $4,600 catalytic converter replacement boost too if my emissions warranty won't valid

 

believe me I found out the hardway

 

Only in America...sigh😕

I ran my decatted sc'd miata on airfield runs in 1993 on racing fuel and my decatted X100 in 2004 on the same...but I was young and stupit* at 28 & 39, but even then knew 104 racing fuel would destroy cats ..doh!

Bet you feel a proper Barry!?

* I can speak American as was married to one for 12yrs

 

Not only is there no benefit to running race fuel if you're not tuned for it but it can actually make your car produce less power..

 

yup forreal i was putting like 110 and 112 racing gas in my tank and almost destroyed my XKR doing that.That is 1 major life lesson that everybody needs to learn from my huge stupid mistake if they Don't learn nothing else cause i don't think nobody on this Earth feel like forking over more than $4,000+ for a car repair bill.I just really wanna look out for all the XKR owners or anybody really that can avoid thinking they boosting their octane rating with racing gas

 

believe me im right around between that age,im 34nah aint ever in my life gone do nothing that stupid no more.Believe that.But the sad thing is I got buddies who race cars they didn't even bother to tell me that when I didn't know.I guess the only thing I can say is WOW some friends i have smh

 

Thanks for the warning!

 

This is interesting to me. I don't have any intention to use racing fuel in my XKR, but here in the UK we have a choice of using 'standard' 95 RON fuel or 99 RON 'super unleaded'. The 99 octane fuel is, of course, quite a lot more expensive. Shell claim it delivers extra power. Now, cunningly, Shell do not claim that the higher octane gives the extra power. In a classic example of marketing-speak, they say instead:

"A nutritious diet helps athletes to perform. It is similar with your car’s engine. Shell V-Power fuels with boosted DYNAFLEX Technology are designed to help restore your engine’s performance."

So this Dynaflex Technology is the key, and if you look into this, you will see it is a collection of various additives, which may or may not have benefits. Read about it here if you are interested:

https://www.shell.co.uk/motorist/v-p...-unleaded.html

But my question is this: do not modern engines automatically adapt or adjust, via their many computers, to the octane rating of the fuel they are consuming? If they do, then putting 99 octane fuel in the tank ought to unleash some extra power. IOW, the engine 'tunes itself' on the fly to use the extra octanes. If they don't, then the 99 RON fuel is a waste of money.

I'd like to know because currently I use the 99 RON in my XKR and the cost difference can be as much as 25 pence a litre (32 cents a litre in US money, or $1.22 more for every US gallon).

So, am I just wasting my money?

 

What I read is that on normal driving, the normal recommended fuel is enough and the engine has max performance. In some demanding situation, maybe heavily loaded, going up hill or WOT, if the engine with the normal fuel starts pinging, ignition timing is reduced to protect engine. This results in less power. The higher octane fuel can therefore in those rare instances provide extra power. Well not extra power, more like the normal, not-reduced power.
Not worth the hassle and money in my book.

 

Barnsie, I am nowhere near as talented in auto mechanics as many others in this forum, but I found a good article on combustion timing here. I take from this article that one way a modern engine adjusts to higher octane fuel is through the knock sensing circuit. Knocking occurs more often when a higher octane fuel is burned in an engine tuned to burn lower octane. But the EMU reacts to knocking by retarding the spark timing so that maximum combustion occurs later after top dead center. This results in a less than optimal conversion of all the potential energy in the high-octane fuel into kinetic energy, but reduces the self-ignition of the fuel that causes knocking.

So, unless other inputs to the EMU or engine modifications result in optimal combustion of the fuel, it would seem that paying for a higher octane fuel than the engine is designed to use optimally is a waste.

I would be happy to hear that I am wrong on this. I try to make my mistakes clearly, so that I may be more easily corrected!

 

Every study I have ever seen says that running octane higher than the stated rating provides no benefit in performance or maintenance. I have a buddy who would run 93 in a car that takes 89 thinking it would "clean" the system. From everything I have researched it is a waste of money. You are better served choosing a station that is Tier 1 if you are so inclined (American designation I believe), they have the better quality additives. The base gas itself could have come from any regardless of brand you buy. Here in my area of the US it is difficult to find 91 octane so I have to round up to 93.

https://www.consumer.ftc.gov/article...0run%20cleaner.

 

i'm glad to help cause that 91+up written on the gas tank is LIES if you decide you want to try and boost your octane levels with racing fuel.Please don't put anything further than 93 octane in the tank or else your catalytic converters have no problem showing you it don't like it.

 

long as it's not 110 or 112 i might use it 1 day.But here in the USA most gas stations only have 93 gas and I would go to this special gas station that sells the racing fuel putting it in my tank sometimes.Idk why shell don't sell that kind of gas in America tho.I can tell you like this,if you don't feel a difference in your acceleration after putting that higher octane gas in your car,then that pretty much is a waste of money.Like for instance,I started putting a lot of valero gas in my car and it dumbed it down in acceleration and then i got it down to a quarter tank and filled it up with 93 shell gas and it gave me the acceleration to throw me back in the seat when barely touching the gas instead of having to push the gas a little further down for that type of launch.I say if you effortlessly have that barely touch the gas feeling for acceleration in your XKR,then that's the correct gas station you need to stick with that's also at a high enough octane to not do damage to your cat converters

 

Thanks tampamark, and the other members too who have responded. I will switch back to the basic 95 RON. I am surprised that in the USA the standard fuel seems to be 91 RON. There is nowhere in the UK that sells such a low octane gas AFAIK. I can't recall seeing any lower rating than 95 here. Interesting. Thanks for the link too!

 

Please correct me if I am wrong, but wasn't your problem the lead in the fuel you used, not the octane rating. I have been using 99 octane fuel ever since I got my XKR (2008 MY) and my cats are purring still.

 

https://fueleconomy.gov/feg/octane.shtml
https://gasprices.aaa.com/fuel-quality/
but I always liked this one:
http://www.aaa.com/AAA/common/AAR/fi...ull-Report.pdf

the better the gasoline the better the detergents. And in some cases the higher the octane, the better the detergents and other additives.
cheers.

 

US uses a different rating, AKI, not RON.

93 AKI equals roughly 99 RON.