SwedeSpeed - Volvo Performance Forum banner
1 - 20 of 64 Posts

·
Registered
Joined
·
1,329 Posts
Discussion Starter · #1 · (Edited)
Updated fuel log using 87 Octane, and testing it against 98 and 93 (oops, that isn't 98.....it should have read 89 of course).
Comparing 87, 89, 93



Here are my recent results with a 2.5 AWD XC70, same drivetrain as the XC90 but less weight.

I believe the 2007 2.5 says you can use 87 octane. The dealership told my wife to use 87 in our 2004 2.5 XC09 and we did for 133,000 miles with good results.
You can see from here, there really is no benefit in milage to use the higher priced fuel. On that one tank fill of 89 octane Exxon I was amazed, and not really sure what happened there, it may have been 100% gas with no ethanol.

21,6 mpg on 87 octane Kroger.
25.4 mpg on 89 octane Exxon.
22.2 mpg on 87 octane Murphy.
20.5 mpg on 89 octane Kroger.
21.4 mpg on 87 octane Kroger.
22.4 mpg on 87 octane Kroger.
21.7 mpg on 87 octane Kroger.
22.4 mpg on 93 octane Kroger.
22.5 mpg on 87 octane BP.
23.3 mpg on 87 octane BP. ( with Mobil-10W30 synthetic oil change)
22.9 mpg on 87 octane Kroger
24.0 mpg on 87 octane Shell (this tank I intentionally eased back to see what kind of milage I could get within reason at 70 and 80 mph)
23.0 mpg on 87 octane Shell
21.7 mpg on 87 octane Shell (this tank was a little more sporting)

I'm presently on a tank of 93 and although the car feels like it runs better, the SOPM (seat-of-the-pants-meter) is notoriously inaccurate. Milage does not seem to vary.

best,

P
 

·
Registered
Joined
·
668 Posts
The other thing you are not reporting is the ignition timing. Most engines that "require" 89, 91, 93 octane fuel can run on 87 thanks to antiknock sensors and adjustable ignition timing and fuel to air ratios. However I have read in owners manuals that this leads to accelerated engine wear. I do believe that if the manufacture recommends X octane and you run at least X octane then you are doing right. However if the manufacture recommends Y and you run less than Y you are inviting trouble in terms of engine life and degraded gas mileage.
 

·
Registered
Joined
·
1,882 Posts
I bet your timing is RETARDED!

94 over 87 with a tune shows me Significant gains.
 

·
Registered
Joined
·
1,329 Posts
Discussion Starter · #4 ·
I bet your timing is RETARDED!

94 over 87 with a tune shows me Significant gains.

Maybe I'm retarded, but rather than go on conjecture I looked it up in my manual. Here is what it says.

"Minimum octane requirement - AKI 87 (RON 91)"





Anti-Knock Index (AKI)

In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, like Brazil, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).


Difference between RON and AKI

Because of the 8 to 10 point difference noted above, the octane rating shown in Canada and the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison.
 

·
Registered
Joined
·
2,148 Posts
the owners manual for her 2.5 XC90 says minimum fuel requirement is premium. she put mid graade in once and said it was sluggish on the hill outside our complex. the four cylinder small GMC I had as a loaner for two days had a hard time on that hill. my 1.8 4 cyl Astra manual has no problem on that hill, and her 2.5 with premium takes it like it is flat when it has premium. thats our seat of the pants experience with premium over regular.
 

·
Registered
Joined
·
1,329 Posts
Discussion Starter · #6 ·
Guys, note this is for a 2005 XC70 2.5 turbo, not the XC90, although the dealer told us to run 87 on our 2004 XC90 and we did so for 133,000 miles with good results and a very strong trade in.

The 87 octane reference is from the official "Owners Manual Volvo XC70 TP7573" Page 164 under the title "FUEL".

Again on page 88 under "FUEL REQUIREMENTS" it says the same thing.

The motor was tuned to the spec in order to pass the emissions testing here in Tn.

All I'm doing is reporting milage and what the manual says.

best,

P
 

·
Registered
Joined
·
1,329 Posts
Discussion Starter · #7 ·
I think octane in general is badly misunderstood and this misunderstanding may even be promoted with a wink by the oil companies who reap the benefit of people buying higher octane unnecessarily. Gasoline with higher octane does not produce more power. It burns slower so that in a higher-compression engine the engine does not detonate. That is all the higher-octane gasoline does. If your engine is pinging badly on acceleration, then a higher octane gasoline would help alleviate that problem. Assuming of course that everything else (timing etc.) is OK.

If Volvo set up the timing, performance, warranty, all things considered, based on a minimum of 87 octane in order to provide all the performance they marketed and engineered, then it would appear to me to be a "waste of money?" to be dumping in the more expensive blend. Certainly my own testing shows NO benefit in milage.


From Wikipedia:

Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.




Regards,

P
 

·
Registered
Joined
·
7,476 Posts
I think octane in general is badly misunderstood and this misunderstanding may even be promoted with a wink by the oil companies who reap the benefit of people buying higher octane unnecessarily. Gasoline with higher octane does not produce more power. It burns slower so that in a higher-compression engine the engine does not detonate. That is all the higher-octane gasoline does. If your engine is pinging badly on acceleration, then a higher octane gasoline would help alleviate that problem. Assuming of course that everything else (timing etc.) is OK.

If Volvo set up the timing, performance, warranty, all things considered, based on a minimum of 87 octane in order to provide all the performance they marketed and engineered, then it would appear to me to be a "waste of money?" to be dumping in the more expensive blend. Certainly my own testing shows NO benefit in milage.


From Wikipedia:

Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.




Regards,

P
It is OFTEN quite opposite - LOWER octane grade have HIGHER energy density...

but...the POWER output can be increased by using fuels of higher grade...the reason - engine can withstand higher compression without knocking...

So, yes to more power, no - to better mileage...


Beter mileage is a function of your right foot...:)
 

·
Registered
Joined
·
1,329 Posts
Discussion Starter · #9 · (Edited)
I understand how this works on higher compression engines and modified engines but on a stock engine with stock compression and timing how does higher octane produce more power?

Regards,

P
 

·
Registered
Joined
·
7,476 Posts
I understand how this works on higher compression engines and modified engines but on a stock engine with stock compression and timing how does higher octane produce more power?

Regards,

P
All (most?) modern stock Volvo engines are tuned for the high octane fuels, so to run on 87, the engine management retards the ignition with all typical consequences, i.e. lower HP and torque at the same RPM...plus, engine is more prone to knocking, and thus requires less spirited driving style...

In our particular family - we drive V8 XC90 on 87, since V8 has an abundance of power for the everyday driving, but we do switch to 91 on our 3.2 S80 in summer, because of pretty prominent knocking during the aggressive acceleration on 87 (I did that a couple of weeks ago, after months of driving on 87).
 

·
Registered
Joined
·
1,329 Posts
Discussion Starter · #11 · (Edited)
So are you saying the engine management system can sense the grade of fuel I am using and changes the settings automatically every time I fill up?

Since all of my driving in a Volvo turbo has been with stock settings, I have never encountered the first knock in our 850, XC90 and now in the XC70. So are you saying if I change from 87 to 89 octane, or from either of those to 93 octane, I will be able to register a diferent power rating on the dyno or quicker ETs wihout touching anything on the car?

best,

P
 

·
Registered
Joined
·
7,476 Posts
So are you saying the engine management system can sense the grade of fuel I am using and changes the settings automatically every time I fill up?

Since all of my driving in a Volvo turbo has been with stock settings, I have never encountered the first knock in our 850, XC90 and now in the XC70. So are you saying if I change from 87 to 89 octane, or from either of those to 93 octane, I will be able to register a diferent power rating on the dyno or quicker ETs wihout touching anything on the car?

best,

P
Yes to all questions. Isn't it crazy?

In my 3.2 S80 engine response is very different on 87 vs. 91 (no 93 in So Cal) and one can tell the difference right after leaving the gas station. The fuel consumption is about the same though.

In V8 XC90, I cannot feel the difference...and I am not THAT involved to put my daily driver on dyno...
 

·
Registered
Joined
·
1,329 Posts
Discussion Starter · #13 ·
Yes to all questions. Isn't it crazy?

In my 3.2 S80 engine response is very different on 87 vs. 91 (no 93 in So Cal) and one can tell the difference right after leaving the gas station. The fuel consumption is about the same though.

In V8 XC90, I cannot feel the difference...and I am not THAT involved to put my daily driver on dyno...
I don't put much faith in the seat-of-the-pants meter (or K&N air filters) so you know what's coming next (the ole 0-100 out on my fav stretch of un-patrolled asphalt, first with the 93 now in the tank, which I am trying, and then another identical run with 87). If there is a validated nanosecond of difference I'll be crowing about it.

Thx for your comments BTW.

Best

P
 

·
Registered
Joined
·
7,476 Posts
I don't put much faith in the seat-of-the-pants meter (or K&N air filters) so you know what's coming next (the ole 0-100 out on my fav stretch of un-patrolled asphalt, first with the 93 now in the tank, which I am trying, and then another identical run with 87). If there is a validated nanosecond of difference I'll be crowing about it.

Thx for your comments BTW.

Best

P
I never being known to worry about seconds to 60...my test is strictly audible...I either hear the knocking and have to ease the acceleration or I do not...the difference is pretty obvious for 3.2, no difference for V8...
 

·
Registered
Joined
·
262 Posts
So are you saying the engine management system can sense the grade of fuel I am using and changes the settings automatically every time I fill up?
Yes and no, the engine management system can measure the difference in detonation timing (knocking or pinging) that results from differences in the octane rating of the fuel that is being pumped through it and change settings (advance or retard timing) on the fly.
 

·
Registered
Joined
·
7,476 Posts
Yes and no, the engine management system can measure the difference in detonation timing (knocking or pinging) that results from differences in the octane rating of the fuel that is being pumped through it and change settings (advance or retard timing) on the fly.
So what does NO part refer to?

grade = anti-knocking index... sensing the knocking (I believe it is actually listening to the audible signals or to the vibrations in audible range) is the most direct sensing of the grade...
 

·
Registered
Joined
·
41 Posts
The '04 XC90 owners manual recommends 91AKI fuel for "maximum " performance and a "minimum" requirement of 87 AKI. As stated previously, the engine is tuned to take full advantage of premium fuel and operates in a de-tuned state when it senses the inevitable pre-detonation(knock/ping) from using low grade fuel in a high compression engine. It's not rocket science, it's engine management 101.
 

·
Registered
Joined
·
1,882 Posts
Maybe I'm retarded, but rather than go on conjecture I looked it up in my manual. Here is what it says.

"Minimum octane requirement - AKI 87 (RON 91)"





Anti-Knock Index (AKI)

In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, like Brazil, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).


Difference between RON and AKI

Because of the 8 to 10 point difference noted above, the octane rating shown in Canada and the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison.
What I meant is that your ECU will pull timing (retard timing) because you're running such a low octane fuel.

Just to clarify I was not implying that you or your car are not operating with a full deck of cards.
 

·
Registered
Joined
·
262 Posts
So what does NO part refer to?

grade = anti-knocking index... sensing the knocking (I believe it is actually listening to the audible signals or to the vibrations in audible range) is the most direct sensing of the grade...
The no refers to the fact that the engine management system isn't actually directly sensing the fuel type when you put it in via some measurement of the chemical composition of the fuel itself and adjusting to that, rather (as you suggest) it's sensing the engine's reaction to the fuel that you put in. As you point out it's a small distinction in practice, but I wanted to be accurate and not leave Mr. P with the potential impression that the EMS was counting iso-octane molecules.
 

·
Registered
Joined
·
7,476 Posts
The no refers to the fact that the engine management system isn't actually directly sensing the fuel type when you put it in via some measurement of the chemical composition of the fuel itself and adjusting to that, rather (as you suggest) it's sensing the engine's reaction to the fuel that you put in. As you point out it's a small distinction in practice, but I wanted to be accurate and not leave Mr. P with the potential impression that the EMS was counting iso-octane molecules.

And I wanted to be precise too...the AKI stands for anti-knocking index, not for the CHEMICAL COMPOSITION, thus ECU measures such index DIRECTLY, by sensing the audible signals, i.e. KNOCKING/PINGING...

Thus grade does NOT directly define the chemical composition, but the potential reaction of engine to the fuel in relation to some theoretical fuel with the AKI 100. 87 and 91 should not be read as %% of some molecules, but as a relative ability to withstand the denotation.

No one suggested chemical analysis, which will be futile anyway...because fuels with DIFFERENT chemical composition have might have EXACT SAME grade, i.g AKI...you should also know that adding Pb contained molecules affect AKI (although making the fuel more poisonous), thus the fuel with LESS iso-octane can have HIGHER AKI, and so forth...

Every major brand puts bunch of crap into its "brand name" fuel, changing chemical composition...

91 Chevron with Techron is chemically different from 91 Texaco with whatever carp Texaco puts in...


Sometimes, reading BETWEEN lines hurt...start with reading what is written...in most cases people still mean what they write...

Here is an original question again...

"So are you saying the engine management system can sense the grade of fuel I am using and changes the settings automatically every time I fill up?"

The most exact answer to THIS particular question is a resounding YES.
 
1 - 20 of 64 Posts
Top