Technically, I don't think the 'term' troll is appropriate here.

I suppose you were expecting some lab results, graphs and charts that show the difference between use of lower octane fuel instead of what is recommended. I'm going to recommend perhaps another source for that kind of information...we have some extremely competent and technically minded individuals as members, but none will be able to provide you what you seek, either for or against your personal choice.

In this case, I think Jaguar engineers may have already done all the hard science and research for us, and I'm also pretty confident that by selecting, and recommending 91 octane or higher isn't going to make them any more money from its consumer...unless the company is some super-secret investor/stockholder of an oil company.

I'm also pretty sure the 3-4 year interval (maybe even longer) inspections made by weights and measures from our individual states dept of agriculture doesn't guarantee that the octane in every ounce of fuel is above the spec, in fact, the allowable tolerance is -0.7 octane units. I wouldn't be surprised if a fresh fuel delivery arrives prior to the routine inspection. Those underground storage tanks do not only hold 87, 89, or 91 octane fuel, there's water and other outside contaminants. There is a good chance you'll get even lower than the posted octane rating on occasion.

I think I'm finished here. Like others, I too have made a certain mental note to myself.

 

Nice thread... Buuutttt... Actually a lot of stations that sell High, Mid, and Reg gas only stock the High and Reg.. Mid is created by a mixing valve at the pump.... Sorry no graphs and charts to show...But a quick way to tell is to look at the refill caps for the holding tanks. They are normally colored some way so the truck driver knows what is what... So, two different tank caps but three grades= blended Mid...

Sorry, I just like to stir up the pot...LOL

 

Too bad the thread went sour, but if nothing else I got an education on just how common the misunderstandings and myths about 'high octane' vs. 'high quality' vs. 'high additive level' gas are.

If the assumption is made that these three elements are one and the same or always moved in lock step then the technical part of a discussion would invariably go off course almost instantly.

 

Hmmmm wait this is probably a stupid question but how different is "true" 89 to mixed 89? call me ignorant but i thought it was bad to mix octanes. does this mean you could mix premium and mid to form a happy midpoint and solve this gas thread once and for all?????? nahh then there would be 3 things to argue about. mikey whats your take?

 

to be honest im really surprised that there hasnt been a "scientific" test on the effects of various grades of gas in engines that call for premium

 

jagv8 has been a contributor? lets see

We all have jag's stated minimum octane. Why do they state a minimum if it's OK to ignore it?

From the handbook:
Use only Premium unleaded gasoline with a minimum anti-knock index (AKI) of 91. Using unleaded fuel with a lower AKI than recommended can cause persistent, heavy `spark knock' (a..

Can't speak for others, but I'm not going to use anything with a LOWER spec than the maker says. I'm not gonna use crappy tires or ones with lower speed etc spec, wrong coolant, cheap filters etc. ...

Jaguar bothered to spell out in detail in the handbook what fuel to use and why. So, hoping that the PCM will compensate (whether by VCT or anything else) outside the specified parameters


i must admit i was wrong for arguing with jagv8 but these aren't the kind of answers i was looking for( not the content but the reasoning behind them). i was aiming at getting answers like i ran mid for 2 years and it killed my cats plugs valves and first born child. maybe that will clear up some of the hate and tension......please

 

Let me throw more fuel in the fire....

how about an E-85 conversion.....

 

All gasoline comes from the same base stock at the refinery. The additives are mixed in at the last minute prior to loading the finished gas onto the delivery truck. Whether this blending is done at the refinery as a dedicated load of mid-grade or is done at the retail gas station pump by combining a half and half mixture of regular and high octane to make mid octane makes no difference. Mixing octane ratings being 'bad' is another myth.

In the heyday of muscle cars, Sunoco stations used to sell gas in up to eight different octane ratings, the highest being the fabled Sunoco 260. This was done by varying the proportions from two underground tanks and blending it inside the delivery pump. Pretty good marketing, I fell for it!

 

Sure- you first. Do we get to point and laugh?

Anybody want to take a guess (no Googling) at the octane rating of E85? How about pure Ethanol?

Here's an easy one- what percentage of ethanol is in E10 and E85? You'd be surprised at how many people get one of those wrong.

 

so if you mix mid and premium would you get a small increase in power?

 

isnt ethanol enriched gas harder to burn so it has a higher octane??

 

Only if the increased octane lessened an existing pre-ignition condition to the point that more spark advance could be applied. If there was no pre-ignition, then no additional power would be available.

All gasoline contains the same amount of energy irrespective of octane rating.

 

So why would you point and laugh? It's starting to catch on with tuners out here in dallas TX.

I personally know a 700whp GT500 running and a 550whp evo9 running E-85 and they smile at the pump.

 

What would you gain by spending all that money to do the conversion?

 

I like this thread. Usually I don't like the endless "which oil (or tire) do you like" type threads since they devolve into interweb finger pointing and dubious "I found it on the intertubs so it must be true" references. But this one looks like it righted the ship mostly on its own. Nice job guys - another example that this is a forum with quality members.

Anyway, Jag says run the good stuff in the STR, so I do. I have a short, stop and go commute. I don't use a lot of fuel really, so spending more for premium is ok with me. I knew this going into the purchase, so no biggie. Rover and Jeep get 87, since they are slugs and drink gas like Charlie Sheen goes through hookers. Saab has a tweaked out turbo, and the Swedes say premium so there ya go.

I will admit to running 87 in my X Type for long stretches with no ill consequences even though Jag said 91. A naturally aspirated 2.5 liter wanting premium...nah.

What I find perhaps most important, is I get gas from the same place every time (Sunoco). I think consistency is a good thing.

I think the "Your Mileage May Vary" (YMMV) could not be applied in a better situation than this one.

 

E85 considerably cheaper in FTW than even 87. So if you convert and get similar efficiency, you "get" lower DOC for your trouble.

Still, I prefer corn be eaten (and traded at mkt price) rather than be govt -subsidized and burnt for for fuel.....

 

Oooooh, sorry, you failed.

Additional question for nobody to answer without Googling. What's the comparison between E85 and and gasoline in energy content?

 

I know when they mix it in our gas we suffer 10% or more.....but without studying the matter.....I had the impression flex-fuel vehicles could achieve near as makes no difference similar MPG on e85? No?
Granted, less energy content but can ramp-up comp ratio for increased efficiency due to higher octane rating.

As I said, I'm opposed principally to the concept, thus disinterested. Also, shocked at how much lower the price is given its increased cost of production....one more source of headache and angst as I write out that check next week!

 

All I know is that the ethanol content causes havoc with my Stihl Farmboss's ability to start and run, and sometimes gives the leaf blower fits. Started using Stabil or Lucas ethanol treatment. Seems to do the trick.

 

1. Ah, yes, Blend Valves. Refineries only make premium and regular gasoline. If the gas station has two tanks, then the mid-grade is blended at the station by a blend valve mixing the premium and regular grades. If the station has three tanks, then the refinery blends it before it is loaded into the tanker.

2. Now here is what needs to be understood about gas and Jaguars. First the history. Along about the late 60's to about 1970, the "static" compression ratio may have been about 10 to 1. However, to make the good horsepower, the cam timing closed the intake valve a good way past Bottom Dead Center making the "Dynamic" compression ratio about 8 to 1. If your engine made 1 horsepower per cubic inch of displacement that was a bunch and we are talking gross horsepower, not net.

Things have changed. Now we have Variable Cam Timing. The ECU can change the cam timing so that we get high power, high torque and good gas milage all in one engine. A 4.2 L Jag engine of 255 cubic inches can put out 294 to 300 Hp net and more which beats the old 1Hp gross per cubic inch being great.

No longer do we have torque curves. It is now pretty much a flat line. The ECU does this by advancing the cam timing at low RPM's and speeds to get the higher torque along with great gas milage. The problem this causes is that the "Dynamic" compression ratio is raised when this is done. This can give you the old "who's knocking in my engine" problem. The ECU can retard the cam timing and spark timing to correct the problem, but the knock sensors have to hear the knock first. The ECU is going to try and advance the cam timing as per the "instructions" in the EPROM. In the long run this won't be good for the engine.