I seem to recall in my business travel days there were countries/locations where 91 octane gas was unavailable. Is that still true or can you get the higher octane gas anywhere in the world. I also didn't see in my OM if 91 octane was "required" or "recommended" . Now I understand the advantages of using 91 or higher but unless it is "required " the timing span can deal with lower octane without any damage but with a loss in power. Is there a Jaguar document that states required vs recommended. As a side bar my kid just got a new Audi A4 which when you read the OM states that 91 octane was recommended but not required. After some investigation the "recommend" allows for usage of 89 or 87 without any long term engine damage. The only drawback was some degrade of HP.
Now I'm not advocating the use of lesser grade gas but just opening up a little conversation.

 

Take a look at your manual index, under Fuel.

My 2012 states under Fuel Requirements that 91 is the minimum. Then it goes on to say that you can go as low as 87 octane but that fuel economy and performance will be compromised. Also it states watch out for knocking, if you get it then it is considered misuse.

My previous BMW had the same octane rating, problem is very few stations have 91 here in Florida. They all have 87/89/93. So I have always used 93, it is pennies difference for the 91 and not worth me driving further to get it.

I have seen folks on the BMW board experiment with using lower octane to determine if it saved money, whether the lower fuel economy was offset by the lower cost per gallon. In the end it was a wash and the car didn't perform as well.

 

91 would be the Norm in Australia. The recommendation for the XKR is 95 here. 98 is available and generally recommended for VW/Audi motors. I know in the UK 101 Octane is available
Cheers

 

US vs EU/AU octane ratings are different. EU 95 = US 91 :
Octane rating conversions - PencilGeek's BMW Blog

 

One of my favourite subjects......

North America is almost unique in the world with respect to octane ratings. We use the 'AKI' system (anti knock index) whereas everyone else uses the 'RON' rating system (Research Octane Number). We used the RON system here till the mid 70s.

Long story short, fuel rated at 91 here will be rated at 95 elsewhere. You may not have seen '91' overseas as that would be '87' in our system, too low a rating for many cars sold there. Fuels of 98 or 100 RON are commonly available overseas.

The usage of lower octane fuel than optimum, say 87 instead of 91, for old school non-computer controlled engines would often result in detonation (knocking/pinging) which could be quite destructive in extreme cases. Today's engines feature knock sensors which sense the onset of detonation and retard the ignition timing to eliminate it. It is the altered ignition timing that may reduce engine power and increase fuel consumption.

I have three modern cars that require 91 AKI fuel. Only one of them (a BMW) shows any noticeable difference when using 87. The Jag and Lincoln couldn't care less.

It is also a waste of money to use fuel higher than the OEM recommendation. If the engine is detonation free on 91 AKI, using 93 or higher will not make it more detonation free.

 

This is very true! I had a friend who used to run 93 octane through his 87 octane car to "clean" the engine and system. It has been well proven that anything above the recommendation is just a waste of money. I use 93 instead of 91 because so few stations have 91 available, there are a couple but at crappy stations that I won't use. I prefer Shell, they have decent additives. This is probably going to start a different discussion...

That is until you start putting race gas in your car. Those who have done that in high performance auto's say it hops the car up pretty nice!

 

There's a very common belief that high octane gas automatically has more or better additives than regular. It's false. An octane rating strictly denotes a fuel's resistance to detonation and nothing else.

Even if there were more additives, if a given car has no contamination issues with regular, there's nothing to be gained by using even more additives or even worse, cans of miracle juice. I don't know of any vehicles (aside from a few with direct injection issues) that suffer from contamination.

As for 'racing gas', there's nothing in it that will make more power. People are very subject to 'butt dyno' miscalibration, especially if they've just payed 2-3 times the price for normal pump gas.

 

If you use a "top Tier" gasoline it doesn't matter what octane as they all have more then sufficient detergents to keep the injectors clean . Look up " top tier gasoline"

 

As Jaguar owners we are very blessed that Jag has not bought into the Top Tier marketing scheme. It also seems that Jag successfully developed an entire family of engines that don't suffer with contamination as compared to some products of other OEMs.

There is nothing in the Top Tier agreement that requires more additives than other non-Top Tier suppliers nor is there any requirement to have just as much additive in regular as premium.

Top Tier seems to be a US-centered thing. Most people here (Canada) have never heard about them and (rightfully so) couldn't care less. There is no 'Top Tier' scheme in Europe or downunder, and also no engine contamination problems. Makes you wonder, no?

 

I in no way meant to imply that higher octane and quality additives go hand and hand. I prefer Shell gas because they have decent additives, but my Shell stations don't have 91 available so I round up and use 93.

The only gas station that offer 91 that I have found is 7-11. I am not a fan of their gas, whether that is a valid concern or not I don't know, maybe I am a rube falling for marketing.

I do know this, the way gas is transported through the U.S. is by pipeline, and that pipeline operates like a bank. If you put in 91 octane in the pipe today you can take octane out of the pipe 3,000 miles away immediately. So Shell may be putting 91 from them into the pipe and BP 91 out on the other end. Once they take it to the local tanks they add the additives which to me are the only difference.

 

Only even heard about it a few years back as a lot of folks on one of my Ferrari forms had numerous discussions on this topic. As for me I've only used Mobile for the last 40+ years so I figure I must have paid for a few drilling platforms by now , hahaha. As for 91 octane we don't have any in our neck of the woods. It's either 87 , 89 or 93.

 

Yes its the same here in New Zealand 91 is the norm, most european cars would run 95 or 98 fuel.

 

What REALLY sucks.... I live in Utah, with the fifth highest gas prices at the moment. Thing is, our "regular" unleaded is 85 octane. The midgrade is 88 and the "premium" is 91. Some stations have four grades; 85,87,89 and 91. Something about at higher altitude = less O2 per CF of atmosphere = less burn = lower octane required. I personally think it is just another way for the oil companies and gas stations to get more $$$$$$$.
So, when our 85 octane is much higher priced than YOU guys' 87 octane (hence 88 price higher than your 89, etc) I get all pissy. Plus, there are FOUR REFINERIES within 40 miles of me!
[/rant]

 

Being that the Jag owners here are a very international crowd, I don't think anybody in the US is going to get much sympathy regarding gas prices.

 

It is true that naturally aspirated engines effectively suffer a compression drop at altitude which is why they don't sell the higher octane fuel in Utah, Colorado etc. if your car is supercharged or turbocharged you need the higher octane even at altitude.

I always buy Cenex because it is alcohol free and refined locally from Alaskan crude. 92 octane. Car loves it. 5.0 s/c F-type.

 

The only performance benefit I've heard of for running high-octane fuel is under high-speed/track conditions, or when slogging up passes at altitude, when the engine is under very heavy load. Yes, the knock sensor will detect and prevent knocking, but the ECM does that by retarding the ignition. So you may not get full power under heavy load, in order to protect the engine from knocking. High-octane fuel reduces the propensity to knock, so the anti-knock measures don't have to kick in as often.

In regular driving, you may get better gas mileage, but the saving isn't usually worth it because of the higher price of the fuel. You won't see any performance benefit. On the track, it may mean you don't have to keep stopping to refuel (I only just managed 8 laps of the 'Ring on 100 RON; probably couldn't have done that on 97 RON).

Oh yeah, prices - today in London, unleaded (95 RON, 91 in US) is £1.10 per litre - $6.31 per US gallon.

 

Your statement presupposes that the engine actually undergoes detonation under the conditions mentioned.

I've yet to see one bona fide example of this happening.

 

"Octane" in Canada and US is (R+M)/2 where R= Research Octane and M= Motor Octane

"Octane" in RTW is Research Octane

Hence the differences above.

Comments above re "Top Tier" gasoline are technically correct but some companies do, in fact, put more additive in their Premium blends. And not all additives are equal.

 

I have a 2000 s type, in the area where the gas cap is specified which octane is recommended. Not sure if it's there on yours but it's a good place to check.

 

Shell gasoline has their premium additive only in the top octane gas (93 for me) It is presently considered the best gasoline on the market. I cant recommend it enough in a Direct Injection engine.

Shell starts selling 'premium-plus' gas