is premium petrol really necessary ?
 

hello fellow jag lovers. i have recently bought a xj8 3.2 1998, its in very good condition but as i go along there are a few things i want to have done and it would be nice to get some advice from knowledgeable people like yourselves if you don`t mind me asking. my first question is do you really need to put the more expensive petrol in the car and what happens if you don`t ? i don`t want to damage it, i want to look after as good as the owner before me did, but at the same time i don`t want to pay more than i have to, i would really appreciate some answers to this please cheers les.

You are NEW, so WELCOME to the real world of motoring.

Your Jag is known as an X308, but dont panic, it resolves nothing.

I run our 98 Octane in ALL my Jags, and always have.

Some of them require our 95 fuel, based on teh fuel cap sticker, but I find they really do prefer the good stuff.

I have experimented with our different grades and although NOT scientific, I found they ALL run sweeter with the 98.

We have some outlets here with Ethanol laced Petrol, and I avoid them at ALL costs.

In USA our gas is %20 ethonal and only 91 octane. My car is fine ( is our premium tho)

No gas sold anywhere in North America is 20% ethanol, excepting E85. The octane requirements of these cars is specified in the owner's manual, usually in the RON scale. Gas sold in North America is rated by the AKI scale- apples and oranges.

According to my indie mine will run on regular gas, I've tried it and it does, but it's going to have trouble with emissions and it will eventually clog the catalytic converter.

The Jaguar V8 engines in the X308 is designed to run on 95RON fuel, which would be equivalent to 90 pump octane or Anti Knock Index (AKI) as used to define gasoline in North America. You can choose to run these cars on higher octane fuel but it is not necessary. If you choose to run these cars on lower octane fuel than recommended then the knock control system will retard the ignition timing.

No sir e85 is 85% ethonal

I use e10 or e15 or e20. Depends on brand name of gas.


Most gas in USA has 1%-9.99% ethonal. I use %20 with 91 octane

Could you give me a link to your station that's selling E20 please or at least the name and address? There's NO cars on the road here that are approved to use such a fuel.

I have no idea if my XJR is 95RON or should be 97/98RON but i run it on 99RON
I use 99 on all my cars (apart from the wife's oil burner)

thank you
 

thank you very much for your advice, i really appreciate it

thank you for your advice i really appreciate it

I own a 1997 XJ6 L 4.0 V.P. .....
I got this car a few months ago from the original owner who was elderly now and passed away years ago.... His wife told me he ran super(93 octain every year he drove it. I wasnt sure if i believe everything an owner tell me when im buying there car... but as she told me they had the oil serviced every 3000 miles .... i found the cam cover and head to be spotless.

I was planning to take a long trip in the jag so i wanted to get my fuel system and injectors cleaned before the trip? Look at my post of the " 4 gas test results" in the X300 area.....

My mechanic said it was so clean in my system that i didnt need it...

Look at the hydro carbons and co2..... he was amazed!!!!!

So i continue to run 93 in my jag for life.... no carbon to clean and it has 133,000 now and i put 4,000 my self

cheers jake

You all should heed XJR Engineer's post. Higher octane gas does not improve catalytic converter life, it does not keep injectors clean, it does not improve smog test performance. It does not prevent global warming not does it promote world peace. What it does is burn slower in the combustion process. If you use a lower octane, the engine might knock from an explosion in the combustion proces, rather than a burn, but the knock sensors should dial back the ignition advance, resulting in less knock and slightly lower performance.

That's good, Jake, but the cleanliness is likely a result of the additive packages in the fuel they were using....'Chevron with Techron" comes to mind. It isn't a result the octane rating, per se.

You might be better off finding out what brand of fuel the PO was using, as you could very possibly be using a different *brand* of 93 octane fuel that doesn't have the same additives.

Cheers
DD

All very true, except that high octane gas doesn't 'burn slower' than other fuels. It's simply less prone to 'self-ignition' or detonation. Changing the burn speed (flame front velocity) of a fuel would not prevent detonation and (in theory) provide more opportunity for detonation to occur.

Doug is correct in saying that there's no connection with octane levels and amount or type of cleansing additives. These cars don't seem to be fussy about fuels in the first place- no real history of contamination or injector problems.

I'm glad Jag (and Ford) never bought into the silly 'Top Tier' marketing scheme like some other OEMs.

Interesting point, because in North America regular is usually rated at 87 AKI and premium is rated at 91 AKI.

Thus, the design point is closest to North American premium.

XJRengineer, could you clarify a point that's still a bit unclear to me please? We have 2 grades of premium in this country, 95RON & 98RON. Although my X300 3.2 is designed for 95, I've been running 98 Shell VPower for a while now in the belief the engine will run cleaner, gaining better MPG and performance (maybe the ad's sucked me in!!). The improved performance I "experience" may be more attributable to other minor mods, including your CS bracket, however the car seems to feel happier on 98. This is just a perception since I haven't scientifically tested the power or mileage economy of 98 vs. 95. So am I really wasting money and would be as well off using 95? I have never tried the car on our standard 91RON, but as a point of curiosity is it logical to assume the resulting timing retardation through knock control would be enough to negate the benefit I gain from your CS bracket?

This is the cleanest emissions tested car i have ever had. I run this test on all of them over the years and this is also the first car ive bought, and first jag ive bought that was recommended to run super 93 from the owners wife.

I cant think of anything else that would help keep my fuel system so clean? I just put 2 and 2 together and the previous owner told me her husband used from the first day until i bought it at 128,000+

Im up to here some explanations or possible reasons for this excellent 4 gas test result? because i get good performance around town and 26mpg on the highway...tks

jake

Jake, read post #14 :)

The fuel that the POs used may very well have played a part in keeping the fuel system clean...but not because it was 93 octane.

Cheers
DD

Tks doug...