Well let me try to explain although I am no expert. We have here temperature ranges from 100+F in the summer to -40F in the winter. We have a few fuel companies selling winter gas. Basically it's a gas and ethanol mix that promotes cleaner burn, reduces carbon monoxide and is usually sold in the winter months because cold engines operate less efficiently and produce more carbon monoxide. I notice no difference in power or consumption when I come across this fuel but I do notice a different smell... not anything big but just different. I guess because it burns hotter and the air outside is cold.

Cheers,

As for a good read on gas...

http://new.api.org/aboutoilgas/gasol...ine-octane.cfm

 

Road trip.

I'm glad that you enjoyed the quality time with your wife. I'm just waiting for the kids to clear off so that we can do the same (several years yet I suspect....).

94 Octane

Now you can understand why I am so frustrated with the fuel over here (the US), when I'm used to buying 95 Octane at my local garage, supermarket or wherever and can get 98 Octane for a small amount extra. Mind you I'm not frustrated about the price (in Holland its currently Euro 1.30 a liter which is roughly $6.50 a US gallon).

89 Octane

I agree with your comments, I don't trust the advice at the moment. I know I'm safe with 91, but I'm new to (a) the extreme cold in the winter (b) the idea of radically different winter fuel (c) fuel of such a quality it gums up your motorbike carburettors during winter storage.

However - there's a clue in the recent reply - ethanol. I will investigate further (ethanol has significantly different combustion properties).

Cheers, Graham

 

Don't worry I don't necessarily want to use ethanol (I've had experience in engineering for the Brazilian market, I know what flex fuels can do). But if the oil companies are reformulating their fuels for the winter with ethanol, I want to research it and work out what that means.

Ethanol may also explain the comment earlier about gas stations putting water in the fuel - the two are so miscible that it is impossible to eliminate water from ethanol (from memory, pure research grade ethanol is only about 96% pure).

I'm sure that the Jaguar engine is flex fuel compatible; the manual says up to 10%.

Anyway, I'm off to sample some ethanol soon at the hotel. Cheers!

 

Well this is an incomplete reply, but the best I can do for now.

As far as I can tell the fuel is reformulated for winter to assist the suspension of condensed water in the atmosphere freezing in the tank. I can imagine there are some anti-waxing agents in there as well. Certainly the freezing of water or waxing of the fuel lines is bad news, and I can imagine if a vehicle isn't used very much, the water will collect at the low points in the system (i.e the tank and perhaps the lines below the floorpan) and freeze.

So my guess is that one piece of advice would be not to let your tank run down completely, in case the fuel pick up encounters collected ice (I have no experience to know whether this actually happens, but I do know that the tank pickup is at the lowest point, and usually involves a gauze type material to "wick" up the last of the fuel).

In really cold weather, the air density increases and so theoretically more oxygen enters the combustion chamber each cycle and you get more power. The automatic instinct is that more power = more potential for knock, so use a higher Octane fuel. However, in this wonderful world of ECU managed engines, knock sensors greatly reduce this risk. Also Jaguar use engine dynos to establish the knock limits and "map" all possible regions within the engine operating range; the eventual vehicle calibration is backed off to a safe limit away from this point.

One feature of lower Octane fuels is that there are less additives to combat knock, and by implication the fuel can burn under more marginal conditions. So under really cold conditions, a lower Octane fuel would help the engine start, and if you are only using the vehicle for short journeys, the faster warm up that may result would be a good thing. I can't imagine that the difference is large, but it may help long term carbon build up or injector clogging.

As an aside, my X type doesn't seem to have the air assisted fuel injectors that are used on the S type and the XJ (there is a passage for air which is blown tangentially onto the injector mist, helping the fuel atomisation process) , and I can imagine that their operating tolerance envelope is narrower. I discussed this with the local dealer and they confirmed that they had more injector problems with the X type than the others...

In conclusion, when I know that I'm only going to be trundling around the suburds of Detroit, I'll try 89 Octane this winter. When I know I'm heading out somewhere, I'll fill up with premium again.

 

I don't know about the fuel being a factor. The market in Detroit is different from the rest of the USA; almost everyone (including me) can get "employee discount" (4% below invoice), and the OEM managers get lease cars and free fuel.

One ramification of this is that there are a lot of Ford employees who get a Jaguar X type with free fuel, because they can.... These car drivers will not worry about the cost of fuel and will just put the high grade in. They seem to be especially popular as second cars, and during the week some of the malls seem like Jaguar factory car parks (Ford wives shopping club). So I suspect that the duty cycle these vehicles see is local shopping, and for the weekend trips its back to the Excursion and polluting the planet.

If misfuelling / ignorance is a factor, I would argue that this would equally apply to all Jaguars, and therefore the difference must be the hardware and perhaps the duty cycle.

I know some of the correspondants on this forum are from Canada; I'd be interested in their input.

 

Todd,

Using anything under 91 octane (that's "plus" in the U.S.) will shorten the life of many of the emissions control sensors. Just something to think about long term, I learned the hard way ($700 in sensors and labor, I just turned 60,000 miles).