Fuel Grade

[PaulE]

Was astonished to see a so-called American expert on the petroleum industry on-line saying with great conviction that using premium grade petrol in an ordinary car is a waste of money and no benefit whatever looked at from mpg, performance, and cleanliness viewpoints.

How do our XJS 4 litre cars fit in?

I have been told exactly the opposite by other experts and look as if I have been "wasting"? money on V-power, and Optimax before that,for years, advice being that it was the ultimate fuel with additives worth the extra cost.

Any comments?

[PaulGover]

I'd vote with the American. Which? and others have tested this many times, and there's usually a minute advantage to the more expensive fuel, but certainly not a cost-effective one. If it's an old, worn, engine, the extra detergents often added to premium fuels might help for a while, but sooner or later it will coke up.

Of course, if the engine is tuned for 4-star or even 5-star, you need the right stuff to prevent pinking/knocking. Some of the earlier V12s might have needed it, but certainly by "facelift" time, 2-star is sufficient, and there is no gain in using better fuel. I presume the 6-pot engines were all designed for 2-star.

Note that not all things are equal in the EU. On the continent, a lot of cheaper fuels contain a high level of alcohol; classic cars don't like that in their fuel, so it's worth paying extra. Ken Jenkins reckons there's about a 10% mpg loss from the cheap stuff too, so there's not much cost difference. But back here on the mainland, there's not enough alcohol in the fuel to be a concern. yet. ...

There is a noticeable advantage in V-power diesel fuel in my X350, especially if I do a lot of short runs in town; about 1mpg better economy, but that's not enough to justify the 10% price premium. I use a tank-full every so often, in the hope it helps keep the exhaust particulate filter clean.

Of course, "your mileage may vary".

[Zennan101]

I can't comment on XJS consumption but for what it's worth my XK8 loved Shell Nitro. Performance improved as did MPG. I was not convinced at the outset but the numbers showed I gained nearly 10% on the MPG which covered the extra cost. Conversely filling up with Tesco regular fuel saw my MPG decrease by nearly 10% which negated the saving.
Only time will tell if the cleaning effect is substantiated.
We all accept that only the best oils and fluids are specified for use in Jaguars by Jaguar cars. I'm going to follow this lead and use only top quality fuel.

[BigCatXJS]

I run my '89 V12 on Shell V-Power exclusively. Runs well with it.

I also use occasionally with my 1994 XJ40 4.0 but I've not noticed any difference so probably wasted ££s.

I have heard that other (non-Shell) premium brands in the UK are a waste of money.

Rich

[paulfrost88960]

The previous owner of my 88 3.6 wrote to Jaguar back in the 90's asking about fuel. I now have the letter that jag wrote in reply and they stated that super unleaded should be used in that engine.