[xj-s] Rec-90 gas

I just drove my 94 conv 6L v12 down to Florida from upsate NY.
Average MPG 17.5. Once down there I found some gas stations that
sell non ethanol 90 octain gas called REC-90.Just wondered if
anyone else has used this gas.–
Bruce Erickson, 1994 XJS Conv. 6L V12
Greene/New York, United States
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In reply to a message from Skyman sent Sat 7 Jan 2012:

How technical do you want?
90 octane is below what your car should have but it will
adapt to the 90 octane because the computer ‘‘learns’’

Minnesota has had that same gas for a long time…
Technically it’s not supposed to be used for road driven
vehicles… Lawn mowers boats snow-mobles, Jet ski’s etc.

Ethanol has 114 octane… if you mix REC-90 50-50 with
ethanol you wind up with 102 octane…

However the unleaded premium (93 octane) starts out with a
base stock of about 85 octane gasoline and added 114 octane
ethanol to it yields out 93 octane…

Since you asked ethanol is a good thing for the following
reasons…
Note: none political
Higher octane.+greater power potential

Extends the number of gallons the refinery can get from a
barrel of oil.+ lower cost per gallon of gas.

Every refinery is different but guessing SWAG 10%
ethanol/gasoline saves you about 40 cents a gallon after
adding in the cost of ethanol…

The engine will run cooler with ethanol

The engine will run with less deposits because of ethanol.

Tune ups will last longer

Injectors will stay cleaner.

Now the Bad stuff…
Gas mileage is slightly worse… Assuming say 20MPG Pure
gasoline would get about 21 MPG to ethanol/gasoline
combination getting 20
(adjusting for say 10 MPG pure gas would get 10.5 MPG and
ethanol/gas blend get about 19 MPG)–
The original message included these comments:

Average MPG 17.5. Once down there I found some gas stations that
sell non ethanol 90 octain gas called REC-90.Just wondered if
anyone else has used this gas.


MGuar
Wayzata Minnesota, United States
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In reply to a message from MGuar sent Sat 7 Jan 2012:

‘’----90 octane is below what your car should have but it will
adapt to the 90 octane because the computer ‘‘learns’’’’

How is that possible? The Jaguar V12 has no knock sensors and
therefore the Marelli ignition computer cannot sense knock and
retard the spark accordingly. As a result, it has no way of
learning, or adapting the spark timing. The Marelli ignition has
a ‘‘Strategy Link’’ that will allow you to use a fuel with a lower
than recommended–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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In reply to a message from lockheed sent Sat 7 Jan 2012:

We’ve had a long sometimes heated debate on that very
subject. In the beginning I was extremely skeptical for
exactly the reason you suggested…
Tests proved to the contrary. A fellow enthusiast
provided actual proof…He filled his car up with 93 octane
and went out to thrash it… Having burned off most of the
fuel he drove back to his shop where he had a very large
oscilloscope. Looking at the pattern of spark you could
clearly see clean ignition… (no knock)
He then filled it up with 87 octane and went out and
thrashed it… when he hooked it back up the spark wave was
showing classic knock patterns… BY the second tankful
virtually all of the knock pattern was gone…
Theory’s abound as to why… a few of us argued it was a
change in driving pattern or outright cheating. (filling the
second tank with 93 octane, or a fuel additive etc… It
might also have been atmospheric conditions.
Common speculation is that it’s the result of O2 sensors
input.
But hey, hook your own car up to a big oscilloscope and
do your own experiment… Maybe you’ll come up with a better
explanation–
The original message included these comments:

How is that possible? The Jaguar V12 has no knock sensors and
therefore the Marelli ignition computer cannot sense knock and


MGuar
Wayzata Minnesota, United States
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In reply to a message from MGuar sent Sun 8 Jan 2012:

Well, unless the ‘‘fellow enthusiast’’ can demonstrate that the
environmental conditions (temperature, humidity, atmospheric
pressure - air density) and the engine temperatures and operating
parameters were consistent throughout the testing comparison, his
assertions really lack foundation. As far as I know, none of the
V12 ECU’s up throught the Lucas CU 36 had any learning capability -
nor did the V12 Marelli CU.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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In reply to a message from MGuar sent Sun 8 Jan 2012:

My '95 does not adapt. It will run fine at 89 octane,
but at 87 oct it has a mild full throttle knock that does
not get better, even after 500 miles.

You sure he didn’t pull the retard plug?

John–
The original message included these comments:

Tests proved to the contrary. A fellow enthusiast
provided actual proof…He filled his car up with 93 octane


CJ95
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In reply to a message from CJ95 sent Sun 8 Jan 2012:

‘‘You sure he didn’t pull the retard plug?’’

Better known as the ‘‘Strategy Link’’ on the Marelli Schematics.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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In reply to a message from Skyman sent Sat 7 Jan 2012:

My 87 XJS loves the stuff . . . difficult if not impossible to find
where I live, but I always buy it when I see it traveling. Engine
runs smoother and gets better mileage.

You do know that you can have someone just very slightly retard
your ignition and get along very well with 89 octane gas at quite a
savings. You will loose performance but not much, and your wallet
will be happy.–
Stan
Williamsburg/Virginia, United States
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Here is a report on with map showing the special fuels around the US to meet emissions / air quality issues. An interesting read and points out the large fuel differences that may affect your engine while others in different locations in the country may not have issues.

A couple of years ago a report on ethanol mixes in gasoline exceeded the pump posting by to to three times. The suppliers are not very good at dispensing a blend.

http://www.kansascity.com/2011/12/31/3346907/kc-areas-boutique-gasoline-is.html

Geoff Green

95 XJS 4.0 conv, 76 XJ-S, 61 E-type OTS, 05 F250 Turbo Diesel, 10 Escape

Keeping track of every Jaguar XJ-S, with your help.
http://www.xjsdata.com

3.6 XJS Register paulzimmer@btopenworld.com

Eventer Register pascal.mathieu@perso.be— On Sat, 1/7/12, Skyman skyman83d@aol.com wrote:

to Florida from upsate NY.
Average MPG 17.5. Once down there I found some gas stations
that
sell non ethanol 90 octain gas called REC-90.Just wondered
if
anyone else has used this gas.

// please trim quoted text to context only