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25%+ increase in milage <SNAP> - SUNOCO ULTRA 94

9488 Views 31 Replies 16 Participants Last post by  Insightful Trekker
This is my first post here. The reason is, I have had nothing to contribute since getting my brand new 2004 CVT several months ago and visiting this site prior to this. But the time has come!

The weather here in NJ has been in the mid to low 40's for some time now and continues in this range. My mileage has been 50 - 52 mpg during this time.

Last week it was time to fill the Insight up. Having read a number of posts here regarding premium fuel, both pro and con, I thought I would give it a shot. I filled it up with SUNOCO ULTRA 94 octane and reset my FCD. After about 75 miles of driving the MPG was stabilizing between 68 - 70 MPG! After another week of driving 300+ miles, the MPG remains the same, 68 - 70 MPG! No difference in temperature, no difference in driving habits or terrain, essentially no difference at all... except the fuel.

Now I understand that there are all sorts of varying opinions regarding this issue, many with what seems to be a good 'scientific' basis or reasoning as to why this mileage increase can not be attributed to the type of fuel. But facts are facts. And I must engage in a psychotic break with the interpretation of reality to deny that use of this particular fuel does not have a dramatic effect on the increased mileage of the vehicle.

I would suggest strongly the use of SUNOCO ULTRA 94 to increase the MPG, or at least try it. For those who may use this fuel and do not have such success, you too must face the reality of your experience, but I would suspect that it has something more to do with engine performance issues than the fuel. Keep in mind, my vehicle is brand new (7.5K miles to date).
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It will be interesting to read what your MPG is a year from now with several switches back and forth between fuel grades.

I more than suspect the biggest % in improvement is one or several other variables beyond brand and octane given your stated 25% improvement. Sadly, its simply the limitation of the chemistry of combustion. Unless Sunoco has _really_ found some liquid "magic" <VBG>.

Keep us posted :!: :)
As analyst I hope you don't draw similar conclusions from the other data you have analyzed. I guess I'm "preaching" to the choir here but such an anomaly in such a short time frame cannot be considered a "fact" without supporting data. Where in relation to a standard deviation does this new data fall? Does this fact alone not give reason for doubt? Time will tell.

With that said its more of an anomaly that your MPG in the past was as low as you stated. Some of the early low figures can be attributed to the break-in wear of the engine and driver in order to attain maximum MPG. The "technical" issues in regard as to what _could_ scientifically and reproducibly explain this anomaly are many. And except in laboratory conditions cannot be reliably isolated. So I don't see the benefit of hypothesizing.

My opinion is that your earlier _low_ MPG was the anomaly, and that you will likely see many more MPG averages in this readily attainable range. :D

The "debate" of premium fuel vs. regular has been discussed in here ad nausium. One thread quite recently. Use the forum search feature if your interested. :)

HTH! :)

<Official road sign in Virginia in the early 70's>
"Everybody in favor of saving gas raise your right foot."
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joecvt said:
You can draw your own conclusions of facts if you are still able to read this post.
Well, my curiosity got the better of me.

Without inviting any type of debate, political or otherwise, the only conclusion that I draw from the above statement as it relates to this thread is confusion :!: :?:

What am I missing :?:

p.s. if you have to get political a PM is preferred but don't expect a reply of anything more than "OK." :)
Sorry Figgy,

A knock sensor works backwards vs. what it's name implies. AFAIK all engines equipped with knock sensors use the sensors to allow timing advancement to the knock tolerant point. The Insight is not an exception.

Agreed the name is counter intuitive, the name for the knock sensors function should be a timing advance sensor. But it was derived from how it accomplishes this task, listen for spark "ping" which is a reflection of timing advance. The back door approach. Done primarily due to the fact that you can only "know" if you've gone too far in timing advance when you've got too much "ping". And is was discovered to be relatively easy to tune a piezoelectric crystal to become "excited" in the spark ping frequency range signaling too much timing advancement.

Engines equipped with such a sensor can dynamically adjust the ignition timing based on the fuel or blend(s) of fuel in the tank, compression decrease (due to wear) or increase (due to abnormal carbon deposit build-up), load, altitude and probably a couple more I can't think of right now.

AFAIK the knock sensor is continuously "active" and monitored. The fuel management program is always testing the limit up to a defined point of knock that would begin to cause engine damage. Its also likely limited via software for emission purposes where knock tolerant timing (advance to just before the knock "damage" limit) would otherwise cause emissions to exceed limits.

HTH! :)
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Not quite sure of how to understand this. Didn't see a %~) emoticon (or something similar). Maybe :arrow: :mrgreen: :?: :p

Don't feel too bad. All the knock sensor posts in here to date have been from the name intuitive perspective (backwards).
Any octane fuel will knock, you simply have to advance the timing sufficiently. Optimal timing varies by octane and other engine parameters, as I outlined above. Optimal timing and engine "life" allows for some _slight_ knock. A little simply means your on the peak of the curve.

Sorry figgy but I'm pretty sure about this. Its not cutting edge technology. AFAI remember it dates to the 70's. Generally restricted to performance vehicles until emissions requirements made it increasingly common in the early 90's.

HTH! :)
Re: Higher Octane - less power per unit?

Hi Kuma,

You are correct in that higher octane fuels have less heat energy. The precise term is detonation not to be confused with pre-ignition (a much more serious mistimed burning of the fuel).

From all the many and different locations of Insighters that have tried premium fuels the additional cost never is offset by the slightly better MPG. However there are other benefits mainly low sulphur. Sulphur will ultimately kill a CAT.

The difference in better MPG from a lower "heat" content fuel can be explained by the time factor for the burn process. By having a fuel with higher octane ignition timing can be advanced to an eariler point since detonation is in part due to peak combustion chamber pressures occurring too early and the piston pushing against this out of time force. This also allows for more complete combustion (more burn time from an earlier spark and slower burning fuel allowing for peak combustion chamber pressures to properly coincide with piston position). Therefore better MPG can be achieved.

SEE the paragraph Energy Content and World War II and Octane:

and an old post here: ... php?t=2978

HTH! :)
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