this might sound stupid, but the xj8 calls for 93 octane or better, what happens if you use 87 octane???

 

You will not develop full power. But if you are not participating in stop light drag racing you probably won't notice it. There will probably be a slight reduction in mileage, also. I have been using mid grade in both of my cars, but I drive so little it doesn't make much difference.

 

I would stick to premium. I think your fuel tank holds something like 20 gallons. Premium is 20-30 cents a gallon more, so that's only an additional $4.00-$6.00 per tank. Well worth it. Plus, if I'm not mistaken, premium has a lot less ethanol in it, if it has any at all.

 

Generally false, not that use of E10 makes much difference.

 

The price difference is at least partially and sometimes wholly offset by the increase in gas mileage when using higher octane. The increase is attributable to increased spark advance. When considering money, miles per dollar is more relevant than miles per gallon.

If the premium being used is ethanol free, the LTFT numbers will improve as well. This effect is repeatable and can be shown using data logging through the obd-ii port. The difference is attributable to the higher caloric content of gasoline as compared to ethanol.

The use of ethanol at 10 percent concentration has been the root cause of at least two manufacturer recalls disclosed on the NHTSA site as described in other posts on Jaguar Forums. Both involved leaking fuel rails. There have also been multiple fuel pump failures laid at the feet of ethanol as well as a couple of .... leaking fuel rails.

Shell V-Power is sold in many markets without ethanol. But, you have to check the pump labelling of the particular station.

 

The short version of my story is that I've been using regular (87 octane) for at least 2.5 years now, with no noticeable difference of any kind.

Octane ratings are also terribly misunderstood. Octane has to do with one thing: resistance to premature detonation (AKA, resistance to pinging).
While E10 fuels will have a slightly lower MPG than pure gasoline, higher octane E10 or higher octane pure gasoline should not have any detectable difference in MPG from its lower octane equivalent.

I am not in any way in love with ethanol, but the myths that have built up around ethanol are simply that - myths. Every car of the class of XJ that is being discussed in this forum was built well after E10 had been ubiquitous for several decades. All "new" (as they're not all that new at this point) fuel seals and hoses have been ethanol resistant since well before 1997.

Issues with ethanol, if any, should be occurring on old cars or equipment. Even then, it should be with vehicles being "revived from the dead" where the reviver did not replace the various "rubber" fuel system components.

Every major manufacturer who markets in the U.S. has been aware that E10 is the de facto fuel, regardless of octane rating, for a very long time now. They'd have to be insane (and I don't think they are) to put together fuel systems with components that are not compatible with ethanol.

Brian

 

And you either misunderstand, discount, or have overlooked the role of active spark advance control used in modern Jaguar fueling systems as well as most contemporary vehicles equipped with knock sensors. The spark advance is again observable long term using data logging through the obd-ii port. There is no guess work involved. Anyone with obd-ii data logging software can plot spark advance, mpg, ltft on a timeline using any particular gasolines of interest. The lower the octane, the lower the spark advance for any given set of engine conditions. The result of lower spark advance for any given engine is lower gas mileage.

Tell that to the Nissan owners of certain 2007 models. Also try that on a JF member who went through 6 fuel pump replacements at the dealer using genuine Jaguar parts ... again a 2007 model. Or the couple of people here with 2000'ish Jaguars with confirmed seal failures on the fuel damper junction on the fuel rail.

 

When I notice any appreciable change in MPG under the driving conditions I've used my cars for over the span of decades then we can talk theory versus practice on spark advance.

I never said the failures previously noted for fuel systems didn't occur.

I think it is beyond naive to attribute those failures to ethanol when millions upon millions of cars, many of the same models and dates of manufacture, have been running on the same E10 gasoline their entire lives without issue.

Like I said before, myths about ethanol are very, very hard to get people to let go of. This is all the more the case because they aren't myths if one is referring to similar looking materials used for similar purposes manufactured before the ubiquity of ethanol in fuel.

This will be my last post on this particular issue since I have yet to see anyone change their positions, regardless of how much data I've produced. This isn't the first forum where Satan Ethanol has been invoked.

Brian

 

I work in the aftermarket auto parts industry, and I can say, without a doubt, that ethanol is a problem. I've seen it.

Also, percentages of ethanol do vary by region and/or particular station. There are very few gas stations here in Michigan that offer ethanol-free gas.

And, sadly, I've heard rumors that it is not uncommon for gas rated E10 to be closer to 15% ethanol. Can anyone confirm this?

 

I haven't experienced any negative issues from ethanol.

As for using lower octane fuels, I haven't yet tried this in my Jag. But I do know my Infiniti M35 (which was tuned aggressively from the factory for 93) would dramatically lose power and knock under performance conditions. To me it wasn't worth the extra strain on the engine & loss of power to save a buck or two.

 

This is true if detonation is actually present, detected by the knock sensor and remedial action (reduction of spark advance) is taken. More importantly, the foregoing must occur for sufficient duration and/or in sufficient frequency for the driver to notice or to affect average/instant fuel consumption.

Typical observations by owners indicate that no real difference in power levels or fuel consumption is noted after switching from one octane level to another.

This infers that our engines are not frequently 'on the edge' of detonation.

 

XJRChad: What I want is proof that ethanol is the root cause. I have, as yet, found no credible controlled studies, or even "semi-controlled" testing using modern materials that suggests that ethanol is the problem.

Just because people see gooey seals, etc., and say it's ethanol doesn't mean that it is.

Systems fail, that goes without saying. If the problem were ethanol, then they should be failing at astronomical rates due to the ubiquity of ethanol, and they're not and haven't been.

The hard data is lacking and the anecdotal data is so far below the level of chance failure when looked at from the big picture that I can and do discount it. It simply doesn't make sense.

Brian

 

Yes, it's primarily members of the flat earth society that makes this claim.

 

Indeed. Given the legal ramifications (and massive fines) that would surely ensue were false labeling proven, it's well-nigh impossible that huge corporations would choose to engage in this practice on a routine basis.

There seems to be no end to the willingness to strain credulity for the sake of a "good story."

The old adage, "If it seems too good to be true it probably is," also extends to, "If it seems too bad to be true it probably isn't."

Brian, who has no love of big business but who also generally presumes that those that run them believe in CYA

 

Thanks for clearing that up. There's a lot of rumors that constantly float around, and it can be difficult to judge fact from fiction.

However, I will stand by my statement about the harm ethanol can do. It may not be as harmful to fuel-injected vehicles, but it wreaks havoc on small engines, carburated vehicles, and boats. Carbs do not like ethanol. That is a fact. We don't even sell the red fuel stabilizers (like Stabil) anymore, because they do not treat ethanol. We sell the marine Stabil for everything now, and there is a big difference between the two products when it comes time to pull whatever they were used in out of storage.

Ethanol aside, I still believe in using the manufacturer's recommended grade of fuel. I don't see much advantage in using premium in a vehicle that calls for regular, but I always use premium in vehicles that require it.

Just my two cents.

 

Now that the classic garden-tool-and-boat issue has been dragged out for another thrashing, here some counterpoints:

1) people have been moaning about malfunctioning engines since the 1930s. That's why the all-hailed Seafoam was invented
http://seafoamsales.com/our-history/

2) Satan Ethanol has commonly been available across much of North America for 20-30 years. The only recent change is labels on the pumps.


There's really nothing new here, just a different whipping boy to blame for events that most likely would have happened anyway irrespective of the fuel. In my case this is deja vu all over again. The last demon that got blamed for everything was Satan Unleaded when he appeared in the '70s.

It is true that a gas can left out in the rain with the cap left off will become contaminated with water, so I do my best not to do that.

 

Indeed, again. For those who think that ethanol in gas is in any way "new," exhibit A:



I also don't know how I haven't had problems with either "stale gas" or ethanol in any of the power equipment I've acquired over the last 30 years or so (I'm a bit over 50, I didn't start buying this stuff as a child).

I have never used Stabil or any of its equivalents. I put my mowers, tillers, string trimmers, etc., away in the fall with whatever gas they happen to have in them. The gas cans stay in the garage with whatever gas they have in them. In the spring, when the season begins again, said gas goes from can to equipment, sans treatment of any kind. I have yet to have any sort of "mass failure" of any sort. Every once in a while I have to have the engines serviced (my latest lawn mower is probably 5 years old and went in for it's "tune up" for the first time). My string trimmers are more finicky, but still it's once every couple of years at most.

I haven't had any of these "eaten alive" by E10, formerly known as gasohol (which started to be used in Western PA, where I grew up, in the late 1970s, which is when I learned to drive).


I am endlessly amazed how "friend of a friend"-type stories take on lives of their own and create these vast mythologies. There are no shortage of actual controlled studies regarding the addition of ethanol and methanol to petroleum fuels. Most of these show that ethanol alone has virtually no effect on the most commonly used contemporary elastomers, when combined with petrol it has more impact than it does alone, but not enough to be hugely concerned about, and that the aromatic content of the base gasoline has an equal, if not greater, effect on the elastomers in most cases. For a portion of one of these articles, see here. There are others and I presume that most people who participate on forums such as these know about scholar.google.com and how to use it to search for peer-reviewed fact-based information.

The collector and performance car worlds are simply rife with belief in `received wisdom` that isn't. (Not that they're alone in this, but that's what's relevant here).

Brian

 

Are you sorry you asked? Go ahead and use it if you want, my XJ8 has been running it for 3 years with no ill effects.

 

Don't ask me why Exhibit A, above, won't open. Lets see if the embedded link works; if not, I can't explain it.

Brian

 

Must be the work of Satan Ethanol.