OK, but were you running on 87 octane fuel, and was it E10? And, for that matter, what method of measurement did Mikey use?

It is Occam's Razor logic to dismiss Staatsof's findings as "unbelievable" and assume Jaguar's instrumentation to be just "onboard entertainment".

E10 gasoline is known to actively absorb water and has the potential to create more corrosive sludge in tanks than alcohol-free gas. There's definitely more to this than meets the eye.

 

Mikey would you mind terribly if I just put you on ignore?

You seem to be constantly trying to impress everyone with just how GD smart you are and I don't mind when you are actually pointing out someone's error as you did earlier but you DO exude an attitude that frankly I don't find very helpful in pondering this mystery.

Here's something else I've learned today (from an engineer). Even though alcohol has a lower BTU value than gasoline it also causes the entire mixture to burn cooler and thus even more energy is lost.

Another variable which I cannot know at this point is the actual tail wind. I didn't detect one while I was outside but it is possible that there was a west to east wind of say 7 mph or even 10 which I did not detect. That would mean bucking that on the way out if it was present and taking advantage of that on the way back for a net of 14 - 20 mph. Though I did get exceptional good mileage on the way out as well so I can't say I think this is true but this was an informal test with VERY surprising results.

I don't think one can simply dismiss all of the result as baloney.

Just saying my test route was too short and that you get variations such as this all the time or that the calculations in the Jag are little more than a toy is rather dismissive and not helpful to the conversations.

I'm hoping you can be a bit more cooperative.

I think this is pretty interesting topic.

It's up to you.

 

Here's my take, FWIW.

Your MPG increase has been variously described as surprising, unbelievable, and a mystery. "Anomaly", then, seems just a small step away.

Seems to me that being able to repeat the test over a couple tankfuls in a more controlled envoronment....like your everyday route to-and-from the office....could possibly yield results that are less surprising, more believable, and less mysterious. And dismissive reactions might be validated....or, who knows, perhaps invalidated.

Cheers
DD

 

Please be my guest if you think that will help understand what actually occurred with your experiment.


Your engineer friend mislead you. The common 'double whammy' myth is as incorrect as the one that maintains that the burning speed (or temp) of gasoline changes with octane rating.

I'm truly sorry if I come off as dismissive, that's not my intent. If I know an assumption to be incorrect and have many years of career oriented experience behind me to back it up, I tend to put out the facts and hope the recipient takes them for what they are. If this puts a stick in the spoke of others that are trying to make this into an alchemist's dream, so be it.

In my mind there is absolutely no mystery here at all. It's all been seen and discussed before:

-it's been stated many times that the mileage calculators are inaccurate at best, even more so when a short drive is used as the basis for calculation.

- the standard decrease in mileage between E10 and pure gas is widely known and accepted to be 3-4%. Laboratory test, chemical analysis and field experience all agree. The proposed E15 will bump that up to 5-6%

Again- if the car's instruments were accurate, for a real 15% difference to be caused either by water contamination or by a higher than advertized amount of ethanol in the gas as has been suggested, the engine would most likely not run at all or poorly at best.

Cheers.

 

So it is, 1 US gallon = 128 US ounces = 133.23 Imperial ounces

Or, converting to the common base of litres,

1 US gallon = 3.79 litres
1 UK gallon = 4.55 litres

3.79/4.55 = 0.832
4.55/3.79 = 1.200

But that aside, the semantics are similarly affected even if one deals only in litres
because the direction of comparison affects which number is the divisor.

Comparing 9 litres to 10 litres, when referencing 9 litres, 10 litres is 1/9 larger and
when referencing 10 litres, 9 litres is 1/10 smaller.

So while the number of 25 percent was wrong, the proper two numbers being
20 percent and 16.8 percent, it is still important to know the direction of
comparison.

Yes, this is entirely pedantic.

++

 

The onboard fueling display does not change its manner of functioning just because
another day has passed or a new tankful has been introduced. It operates consistently
all the time.

While it may have an error factor, the error remains consistent for similar use.

Thus, the fueling display should be regarded as a reliable indicator of relative
changes in fuel economy.

If one filled up a second tank with the same gas from the same pump, but the
fuel mileage dropped then one can easily surmise that the fuel mileage dropped
but not exactly how much.

This is analogous to a water temperature gauge that has an offset error.
One always knows that the temperature is hotter than it was, just not
exactly how much.

If the onboard fueling display were wildly inaccurate, there would be frequent
posts of complaints.

There are not.

Most people understand that the instrument has an error factor, but are knowledgeable
enough to treat it as a reasonalby reliable indicator of relative performance.

Of course, if one is sufficiently a***, one could calibrate the readings against a
known large quantity of fuel over a known distance and speed. Not by
pumping in some gas from a station pump, or using mile markers, or the speedometer
but by using laboratory grade instruments with traceable calibration to a standards institute such as NIST. Oh, and independent qualified observers would be nice too.


++

 

His report was a first result.

However, I have posted in this thread and other threads that I have also observed the
same behaviour on multiple long trips, at the same cruising speed, over the same route,
over a period of a couple of years, and used obd-ii data logging as an adjunct. No
powertrain changes, not even tires.

That pretty much makes it repeatable. And repeatability is one of the prime tenets
of scientific testing.

The post is here:

https://www.jaguarforums.com/forum/s...62/#post951706

++

 

What is Occam's Razor?

For those who are interested in knowing whether it has been
properly invoked.

Fallacy: Red Herring

seems more appropriate

 

A full 15% improvement? Or the less surprising, more believable, and less mysterious 3-4% improvement, which is typical-ish?





We know

That why I was wondering if/suggesting the OP could repeat the 15% improvement he reported




That link just takes us back to this very thread !

Cheers
DD

 

This would be accurate over a prolonged period with multiple tanks of fuel. The more data points the better. What has happened in Stattof's case is two, separate abbreviated test periods with relatively few data points.

Kind of like taking a person's blood pressure on two separate days and attributing any variation to something they did differently between the two.

I've proposed that the OP go out and try resetting his calculator at random intervals to see the variations that this can induce. As easy as it is to make mine display 30 mpg, I can also make it display 15 or so.

 

At the risk of keeping this thread on topic....

In my experience the grade of fuel you run makes a BIG difference to economy, and I have seen it first hand in my XJR.

Hypermileing an XJR...

Those octanes are RON, which is not directly comparible to the AKI method in North America.

That run in Germany was with the cruise control set on 160km/h (100mph) hence the higher consumption than "normal"

The fuel in Europe has no Ethanol in it AFAIK. And in Australia the higher grades don't have any Ethanol, except the local United 100, which I don't use.

Given the choice I will not run any Ethanol in my vehicles.

Here in Australia, the Shell V-Power is only 98RON, down from the 100RON that we got in Europe. I've not seen anywhere near the same economy since moving down here.

I did an 1800km road trip a couple of months back, the best I could get was 8.5L/100km at an average speed of 117km/h. Back in Switzerland I would be in the 7's with the 100RON fuel at that sort of average speed.

Hardly scientific evidence, but I have noticed a difference.

 

I'll just say this before concluding my comments on this particular experiment.

I can't repeat this very easily because of the complete lack of gas without alcohol in the state of NJ unless I want to $9-$10 racing fuel. That's not going to happen nor would it be valid. I also have to drive a couple of hours to even get to a gas station that sells the standard no alcohol gas. This was a quasi convenient opportunity based experiment. If it can happen again then I'll try it again.

Now ask yourself this. How often have you done something as innocuous as this that had this much of an effect on your fuel consumption? I have never seen fuel mileage vary this dramatically. You really notice that sort of an increase just by casually looking at the gas gauge and considering the distance you've traveled. You don't have to get out a calculator to know something is up. So this is not an insignificant amount of an increase. This was over a relatively identical path of travel too.

So perhaps Occam's razor (gotta be the most overused ego boosting reference on internet chat rooms) could also be applied in this way.

Something in that tank of gasoline created quite an improvement in mileage.
Exactly what in that tank made my Jag run more efficiently is more complex but that it is due to that tank of gas is simple to conclude.
And no Mikey, it wasn't due to opportunistic resetting of the trip computer to obtain fantastic results.

I've never been able to obtain mileage numbers anywhere close to this in this car before.

And ... Mikey your last two posts are perfect examples of the pedantic and arrogant style that characterizes you. That non apology apology was the icing on the cake. Look up contrition sometime. You could use some.

On ignore.

 

The only person remotely involve in this test was me.

Yes I characterized it as unbelievable because I really wasn't expecting this big a change. Those other characterizations are second hand and red herrings at best. Some appear to be quite intentionally so. We have at least one very close mind in this thread. I won't bother with that one any more. he's stated what he believes to be the case almost from the beginning.

Now if I were to use a test course of driving to work it could vary so much around here that I don't it really would represent much of anything . Maybe over several months it could but that's impossible to do for the previously stated reason of a lack of availability.

Believe me, if I could get that gas I probably would!

Inspite of "some" protestations given what I know of the course I took that day and the traffic conditions I'd say they were almost made to order for this sort of a test.

I had to try and save gas on the way out due to circumstances and I was bale to replicate that on the way back. Once I got close in to NYC where conditions deteriorated I took the snapshot and made not of the results.

But this also bears noting. I WAS consciously trying to be very efficient. Had I been enjoying the newfound power a little more perhaps my results would evaporate somewhat. Besides, I'm not sure how one drives "in a sporting manner" for 80->120 miles both directions in exactly the same way and not get arrested. In Nevada possibly in the NYC metro area no!

Even if one were to knock off 25% of the resultant improvement and call it an inaccuracy discount for Jag's poor instrumentation 3 MPG is still one hell of an improvement.

 

3 mpg difference is not likely based only on the difference between E10 and plain gas. Like Cambo351, I found a significant increase in mileage when I switched from 91 AKI (about 95 RON) to 94 AKI (about 98 RON). This test was done between 2 Chevron stations 250 miles apart, identical return route, identical weather conditions, identical average speed 105-110 kmh (65 mph) and the volume of gas consumed measured by refilling the tank at each station.

91 octane with E10..... 24 mpg
94 octane no alcohol... 27.3 mpg

Octane is not measurable by the average motorist, and we assume that a pump marked "91 AKI" is indeed 91. It might just be, intentionally or otherwise, that good old Regular was dispensed under the label "91". These things do happen from time to time. Just Google "Regular sold as Premium".

 

Amazingly similar numbers ... You wouldn't be pulling my leg?

I know the engines ECU can reduce performance via ignition timing and can even interrupt cylinders for traction control but what's not clear to me is if I put in a higher octane rating such as 100 as found in racing fuel will it take advantage of that? I typically use 91 though 94 is available at Sunoco stations here. I've never checked for a difference nor have I noticed anything like 3pg better. That I would notice. So maybe I'll try a full tank Of 94 next time I go out there. BTW that's not what I had in there on the first leg of this test. It WAS 91 or said so on the pump.

I could call that gas station in PA and ask them ...

Their gas was $4.40 US a gallon as opposed to $3.75 a gallon here in NJ. I think a lot if not most of that is the difference in taxes.

 

At the risk of inadvertently offending even more people, I'll throw another of my two cents worth in.

The theory has been presented many times that if fuel with an octane rating higher than specified by Jag (generally 95 RON/91 AKI) is used, an increase in fuel mileage can be observed. Some also claim 'more power'. The explanation behind this is the higher octane allows the ignition timing to advance, allowing the engine to run more efficiently.

The problem with this theory is the engines have no direct method of measuring octane level to determine what advance ignition curve is most appropriate. Instead it relies solely on the presence of detonation (knock/pinging) as a signal to retard the timing until such time as the detonation is eliminated. The effects of severe or prolonged detonation are well documented. Those of us grey hairs that had pre-computer controlled pre-smog high performance cars may have learned lessons that hard way. I sure did.

I have been taken to task here several times for having used 87 AKI in my own car, with predictions that I am doing irreversible damage to the engine through detonation. It's been almost 10 years and coming up on 120,000K that I've been doing this with no visible negative signs, but more to the point I see no decease in fuel mileage (using more fuel) or decrease in power which would correlate with the knock sensor coming into play. There are many other S-type owners with the same observation. This infers that the engine is not operating frequently at the 'ragged edge' of detonation and needs to retard timing for extended periods to protect itself.

Back to the point. If reduced fuel consumption was actually achieved while using 93 or 94 AKI fuel, this could only occur if the engine was experiencing detonation while operating on 91AKI, the fuel recommended by Jag. It would also mean that the periods of detonation and the resulting retarded timing would have to take place for extended periods of driving- long enough that it shows up in fuel consumption.

If there is a serious possibility of engine damage from detonation, and we're now saying that the only way of completely eliminating detonation (also allowing the engine to run a full advance) is to use 93-94 AKI fuel, why on earth is Jag recommending 91? Why would Jag not just limit the ignition advance so that no detonation occurs on 91?

Or possibly are we looking at yet at another unconventionally coloured fish?

 

Absolutely not. In fact, check out post #51 from Cambo351, and you'll see he got the same sort of result. When I submitted my result to the forum some time ago, JagV8 thought that a 3-mpg increase from 91 to 94 octane was quite likely.

When Jaguar says that 91 octane (95 RON) is the minimum required to avoid engine damage due to detonation, I assume it means the STR might run even better with higher octane gas, if the car is driven briskly. That's why I use the highest octane available. Not everyone agrees.

When Jaguar says that when using gasoline/alcohol blends, if owners noticed differences in operation, they should "resume use of of alcohol-free gasoline", I assume it means that those unspecified differences are undesirable. It's significant that forum member Brutal has described E10 as "crap". For those sort of reasons I try to avoid using E10. Not everyone agrees.

 

Here's an example of higher octane making more power

https://www.jaguarforums.com/forum/p...e3/#post510598

 

There's a bigger blower involved in that case right?

 

For a lot of American this is not a realistic option. There's talk of going to E15 which simply won't work in any of the older cars so I have no idea what they're thinking.