Step out of the car sir and blow here.
Just kidding. Actually that sounds expensive.

This is the easiest and by far the least expensive test for ethanol in your fuel. You will be able to catch the fuel stations lying with this one.

First you will need an empty glass bottle or other fuel proof clear bottle with a screw on lid or a stopper you are sure wont leak or fall out. The Übergeeks may use a nitrile stoppered graduated cylinder if desired. We use orange crush bottles at the dealer. Just be sure it is large enough to hold a meaningful amount of fuel. Using a sharpie or some other marking system that will stand up to possible fuel exposure(my bottle has been in use for 6 months with no deterioration and is marked with sharpie) mark your bottle in 1 inch increments up to 5 inches so it looks something like this. Metric weirdos can substitute centimeters but I would use 2 centimeter graduations, it will be easier to see.



Now, if you would like to test the fuel that is in your car at this moment you will need to take a sample from the fuel rail schrader. If you do not know how to do this find someone to help that does. Gasoline is highly flammable and should be handled with care. An accident pulling a fuel sample from a hot engine could be catastrophic. If you are not 100% sure you can do this seek professional help. Obviously no smoking anything during this procedure. Collect your sample in a clean fuel can or other suitable fuel proof container. You will need only enough to make up 4 inches in your test bottle so the larger your bottle the more you will need. Here's the beauty of this test. You can test on the fly at your local filling station!!!! Just prepare your bottle ahead of time and take it with you along with a fuel can as it is against the law in the U.S. to dispense fuel into a glass container.

Using a small funnel that fits the opening of your test bottle fill to the first inch mark with clean tap water. Try to be accurate here. Your accuracy will depend on the accuracy of your markings but what we really want to know is whether the fuel we use has more than the government(U.S.) allowed 10% ethanol.

Now fill the rest of your bottle up to the 5 inch mark with your fuel sample again being as accurate as possible. Keep in mind that we are not creating a new rocket fuel, pico-liter pipettes are not necessary. Attach your cap or secure your stopper so that nothing can leak out. Shake the bottle vigorously for 10 seconds or so. Let bottle settle and see how much above the original 1 inch of water mark the new "water" level is. Your water sample has absorbed the ethanol from your fuel sample. Very easy, no? Nearly free.

Now, since you had 4 inches of fuel to start with each inch is 25%. Therefore if the new water/ethanol line is at the 2 inch level your fuel had 25% ethanol. If it is at the inch and a half level you have 12.5% ethanol. I wouldn't expect to see much above 12.5% unless there is a real problem with your fuel distributor but don't forget 10% is the max allowed by law.

Needless to say Jaguars do not like ethanol whether it is legal or not. We don't go around testing fuel samples at the dealer so we can strain the ethanol out and drink it. We test so that we can recommend to our customers to try a different filling station that does not use as much ethanol. Your Jaguar will appreciate it and so will you through better performance and better cold starts when it's 0 outside.

Now that you are done with your test you can carefully pour the now pure fuel back into your car and dispose of the water/ethanol mix with a shot glass(just kidding again, though we do usually pour the fuel back in the can or tank.)!

 

I've been using 10% ethanol gas at every second or third fill up in my 4.2 S-type since the day I bought it and have noticed NO loss of power or difficulty in starting with temps as low as -30C.

I've also used it in my early 70's Corvette and my other cars for at least 15 years with no ill effects.

 

Nice tip, I have no idea what we have over here, so will give this a go out of curriosity.

I presume that is the same for both 95 and 98?

Now all I need to do is empty the Gin bottle. Ah well, in the quest for knowledge~)

 

Every area of the U.S. uses their own special blend and I would assume that Canadian production runs along the same lines. Here in the Motorcity we have had some of the worst fuel in the nation for many years and this fuel has caused nothing but trouble for Jaguars. It has been a source of trouble for Jag owners in south east MI and north west OH since the release of the X-Type which began the micro sized orifice in the fuel injectors. In fact it was causing so much trouble in Florida and some other gulf coast states there is a TSB about it.

I'm not suggesting that every Jag owner run out and test a fuel sample. What I am suggesting is that if you have persistent cold start or rough running problems that never seem to be correctable and no explanation can ever be found perhaps checking your fuel is a good idea. In the last 10 years I have asked many of my customers where they buy their fuel. I can tell you which stations local to the dealership are selling good fuel and which are not. Nearly every time I suggest changing stations to a customer I get a call or letter thanking me for making their Jag run better than it ever has. The proof is in the results. Any of you that are blessed with good fuel at every station should be thankful you don't have to deal with a problem that's hard to avoid around here.

 

pretty cool experiment... you just finish watching Bill Nye, the science guy?

Maybe i'll show my nieces, they're always looking for new science projects... tornadoes are so 'last year'

 

Real Tech, just a silly question to ask: is there anything special you need to do if you have run this questionable fuel in your car? I only ask as I have noticed my fuel mileage starting to take a nose dive and after seeing this, it may be part of my problem (also thinking maybe the TPS is starting to go due to driveability concerns too). I have gotten gas from NW Ohio gas stations a little bit from when I have been visiting family in Toledo. I used to get about 26-27 mpg on the highway, but over the last year or so, it has dipped down to where I can barely pull 22 mpg on the highway. I'm not driving any differently.

 

You seem to be up on things with your Jag so I will assume you have done the basics like injector cleaning, spark plug replacement or check, air filter etc. I wouldn't necessarily worry about an occassional tank of fuel with the max 10% ethanol. Honestly it is difficult to find a station that doesn't use the max allowed in my area. My usual recommendation is to always buy fuel from the same name brand station near your home or work for a month and check your mileage during that time. Consistency is the key to establishing a baseline that will allow you to check for differences when you switch suppliers. I realize some people must drive all over the place for work or family and this may not always be an option but without a baseline to judge from trying to determine whether the problem is with the car or the fuel can be difficult. Sensors responsible for fuel mixture like mass airflow, map, coolant temp. and o2 can begin to fail but their output remains within the allowable range as determined by the ECM. Except for the coolant temp sensor which could be checked against an accurate thermometer reading the only way to tell if something is drifting out of range is to check it against a car known to get better mileage. Not always easy for an owner in his driveway. Perhaps this is just another reason to take your car to the dealer on occassion. As a Jaguar tech I have driven at least 1000 different X-Types. I have a pretty good idea of the difference between one that is running properly and one that is not and my opinion isn't jaded. What I mean by not jaded is that I don't drive a single X-Type every day, I haven't gotten used to its ideosyncrasies. Whenever I think along these lines it always reminds me of wheel bearing problems. What do wheel bearing problems have to do with mileage you ask? It goes like this. A customer brings their car in for service and says that a friend was riding with them the other day and asked "what's that horrible noise?" to which the owner responded "what noise?". I get behind the wheel to test drive and 100 yards down the road I say to myself "holy sh*t!!! The hub must be cutting through the steering knuckle on this thing". Don't think this is a joke I have seen this many, many, many times. What happens is the wheel bearing fails so gradually that the daily driver never notices the noise, it has just crept into his daily routine. Then someone else gets in the car and says "dude, what the hells wrong with your car". Happens all the time. Now, if a driver can drive until the wheel bearing is grinding into the steering knuckle and not notice, how long do you think that driver could drive with a gradual decline in performance without noticing? I would say a very, very long time because even if a friend gets in the car, that friend is unlikely to notice the lack of performance without an unusual noise to back it up. I, on the other hand can get behind the wheel of your car and in a 5 mile test drive give you options on 20(an understatement for most) different repairs your car is in need of. Whether you choose to have these repairs done at the dealer or do them yourself, at least you will have had an experts opinion for at most 2 hours labor charge for a complete checkout.

As for your mileage. After establishing a baseline, substitute a different map, mass air, coolant temp etc. sensor 1 at a time and see if any change the mileage. Give each a full tank and reset fuel adaptives at each change by disconnecting negative battery cable at battery post and touching to positive post for 1 second. If you had a friend with another X you could compare readings of various sensors but a larger sample group would be better and again that isn't always easy.

Good luck.