I wonder why we have 'mid grade' gasoline at all. No OEM I'm familiar with manufactures any car that requires it, they're either 'regular' or 'premium'. One other other.

Clever marketeers once again, upselling a customer any way they can.......

 

Actually, that is true. One of the crazy chemical properties of water. This is sometimes called the Mpemba effect. Also, it is the only thing that expands for a period of temperature while frozen then resumes contracting. Water.... some crazy stuff....

Now back to your regularly scheduled gasoline debate.......

 

Probably driven more by regulation then anything else. Probably not allowed.

 

WOW! Something I can expose Mikey to! Weeeeeee!

For the record, my owners manual states that the 5.7's recommended fuel is 89 octane. Mine just happens to be tuned through an aftermarket tuner to run on 93...

Also, the manual specifically states that running anything higher than 89 is of no benefit.

Again, unless you reprogram the car to run on it.....LOL

 

How about that. I've always thought a day was lost if I didn't learn something.

On the other hand the so called Mpemba effect is one of the best kept practical jokes around. The premise of a 1960s Tanzanian student making ice cream in secondary school, part of which included 'heating it', and comparing it to other samples of ice cream is about as improbable and far fetched as it gets.

The only way the experiment can be duplicated (until today) is if the hot water is also cleared of impurities and gasses, ostensibly during the heating process. If the two samples are equally pure and of the same volume, the cold one will freeze first.

 

Ouch...... and that was actually taught in chemistry class.

Well, I'm still at 50%...

 

As were we, except that my prof was a 'show me' type and decided to see if any of us could replicate the results. The closest we got was using distilled water noting that occasionally the hot sample stared to skim over with ice before the cold sample. The cold sample always froze solid first, by a large margin.

I got to know my prof socially years later, and asked about the experiment and his 'challenging' the curriculum which seemed rather daring. Turns out that he had a rather heated discussion with one of the other staff members over the validity of the theory and how the scientific community sometimes accepts things no matter how outrageous the story might be.

Given Al Gore's global warming and cold fusion, guess he was right!

 

If it weren't for this unique property of water, life on earth would not exist.

 

Cold fusion was a silly mistake I understand involved palladium which has weird properties with hydrogen.

Global warming... well, something's happening and is to be expected when you excrete vast amounts into the environment you also live in (such as a teraton or so of CO2).

 

Not true. Some of the highest cars use 87 octane. At cruise you are only producing 35 to 40 Hp.

 

You'll produce it badly with the wrong octane fuel - 87 isn't meant for our cars.

 

Only if the knock sensors are detecting detonation and are pulling timing to compensate. Otherwise, meh.

My own experiments with 87, 89, 91 and 93 show no variation in fuel consumption and no apparent difference in performance. I managed just once to get some audible knock while using 87, but it wasn't easy or repeatable. I've got a 5 hour road trip planned tomorrow to go look at a boat, and gas prices are 'up' lately so I'll be tanking up on 87.

 

Who opened this door again?

If we're talking AKI (anti-knock index), 91 AKI is 95 RON, 93 AKI is 97 RON, so no problem. But 87 AKI is 91 RON, and my S-type Jag manual says that vehicles are specially calibrated for 91 RON only in those countries where 91 RON is the highest octane available. My S-type manual says:

"The preferred fuel should have an octane rating of at least 95 RON.".

...and then:

"Using unleaded fuel with an octane rating lower than recommended can cause persistent, heavy 'spark knock'. If severe, this can lead to engine damage.".

To be fair, Jag does also state that "occasional light knock for a short time while accelerating or driving uphill may occur" implying that no serious damage will result, but why take the chance just to save $5? I personally believe that damage from detonation is cumulative (like mercury poisoning), and you may not realize anything is wrong until it's too late. Obviously, not everyone shares that opinion.

I have tested 91 vs 94 AKI premium on a 5-hour cross-mountain road trip in my STR, which I made twice in 1 week last year under identical conditions of temperature and weather. Recorded 24 mpg for 91 AKI, 27 mpg for 94 AKI, just as generally predicted, so at least some of the savings are lost. (24 mpg in Canada is nearly 29 mpg in the US).

 

Yes, who indeed.

You are correct that damage caused by detonation is cumulative. The problem is that no one can apparently produce evidence of detonation-induced damage on our engines. Putting this together with little or no credible evidence that S-types operated on lower levels of octane suffer loss of fuel mileage may indicate that

a) the knock sensors are very effective in quelling detonation which is why there's no damage

b) the knock sensors are called into action so infrequently that mileage is essentially unaffected.

Not sure who 'generally predicted' an increase of almost 13% in mileage when using 94 over 91 octane.............

*edit* Ooops, clicked too soon.

If you did achieve the claimed 13% increase, the only possible explanation is that the car has continuously been exposed to detonation while operated on 91, which caused the knock sensors to pull some timing. As per your own analysis, damage from detonation is cumulative so it would seem silly of Jaguar to release cars essentially tuned to ensure self-destruction.

 

I'll be watching for this ad....

Jaguar for Sale by owner

Beautiful car, very clean inside and out. Experienced owner has always used Regular fuel to keep running costs down, ignoring Jaguar's recommendation to use Premium minimum 95 RON fuel. Possible cumulative damage to engine, but no problems noticed to date, engine never stripped and examined but should be OK.

Please send all expressions of interest to member xxxx, Jaguarforums.com.

 

Well those numbers, 24 & 27, mpg work out this way in the US.

1 gal US = .8326 imperial so ...

19.91 & 22.48

There's no way I can average 22.48 for an entire trip using our 10% ethanol gasoline but somewhere in the 20-21 is possible if I drive like a little old lady. With that sort of driving the lower octane probably isn't an issue. But the savings isn't that great and I'm no LOL. I used non premium for several tanks fulls during the aftermath of hurricane Sandy. I had no choice. I noticed nothing but then the Sat. night drags were cancelled anyway ...

 

I think our fellow member RobinB may be confused again. If he's using the car's computer for the quoted 24 mpg, it's already calculated in US gallons. One of the quirks of the Canadian version of our cars is that it displays in US gallons rather than real gallons (?)

It appears that the discussion of using octane higher than 91 AKI was also lost as (if true), it would mean that he has been operating his own car under conditions that produce detonation. Seems that point was lost.

Or the supposed increase in mileage when using 94AKI was as imaginary as the supposed loss of mileage experienced when using 87. I wonder how my highway trips where I see 27 or 28 avg/32 peak mpg while using 87 AKI are explained.

Almost time to go , that boat is calling me and spring is coming

 

Yes, thank you, you are absolutely correct.

But no confusion elsewhere - I convert liters to imperial gallons and kilometres to miles before calculating mpg.

Except for that mileage trial I use Chevron 94 AKI premium because, among other things, it contains ZERO ethanol - that fact alone guarantees better mileage than 87 Regular, or any other blend for that matter.

I wonder how Jaguar would respond if asked this question:

Person A always runs their S-type on 87 Regular gas with 10% ethanol.
Person B always runs their S-type on 94 Premium gas with 0% ethanol.

Which person is more likely to accumulate engine damage due to detonation?

 

I'm afraid you are indeed confused. Your mileage figures of 24 and 27 above are already stated in miles per US gallons so there's no need for Staatsof to convert them yet again. There's no real need to do any manual calculations anyway as the car is more than willing and able to do it for you. Just push the mls/km button on the dash.

Even though switching tracks from 'octane' to 'ethanol content' is technically a hijack, your point about variations in fuel consumption when going from pure gas to E10 are well taken. The known energy loss of 3% cannot be denied.

But there again, look at the photos taken today of the results of my round trip to go see a boat (no deal BTW, poor condition). I think 30.7 miles per US gallon trumps your claimed 27 quite handily. This was on 87 AKI fuel, 10% ethanol. 207 miles, 54 mph average.

Maybe you should see about getting your car fixed.

You've yet to address the point above about the detonation damage and mileage loss caused by using 91. How about that?

 

Sigh... here's the data for one of those trips:

(94 AKI fuel) Distance 374 km, 38.7 litres to refill = 27.3 miles per imperial gallon = 22.7 miles per US gallon. Average speed 106 km/hour.

That's very good indeed, considering that your vehicle is rated at 15 mpg city and 24 mpg highway. See [url]www.fuelconomy.gov.

I used 91 AKI (95 RON) for 1 test trip only, otherwise only 94 AKI (98 RON). Your point that "the only possible conclusion is that the car has been continuously exposed to detonation" is ludicrous unless, perchance, you were thinking about your own car.