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Discussion Starter · #1 ·
Does higher OCTANE equate to better gas mileage?

So far, I'm not seeing much of an advantage to 89, 91 or even 93 octane in the tank when it comes to improved fuel efficiency, just better wallet efficiency.

The engine does run more smoothly with anything above 87 though, and is a bit quieter overall - very noticeable at idle.

(in theory, 0-60 acceleration times should drop with higher octane, but I haven't spent much time yet with my right foot pressed to the firewall.)
 

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Octane rating is the ratio of octane (an 8 carbon chain molecule that burns slowly and requires higher temperature and pressure to ignite) and heptane (a 7 carbon chain that is more unstable, and tends to explode rather than burn, and it does so at lower temperatures and pressures). Higher octane means a fuel that burns slower, and is less likely to detonate prior to the spark plug firing. Running low octane fuel, in an engine that does not require premium, will actually make slightly more power (in the neighborhood of 1% or so) because the flame front moves faster, and is the equivalent of slightly advanced ignition timing. In an engine with high compression or a turbo that requires high octane fuel, running 87 will cause ping or detonation, and the engines knock sensor will pick that up, and retard timing or enrich the fuel mix, both of which reduce power and performance. Using the fuel the manufacturer recommends will give you the best mileage, though as always, your mileage may vary and driving habits and overall engine and car condition and maintenance make a much larger difference in fuel mileage than brand or octane rating.
 

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Discussion Starter · #3 ·
Octane rating is the ratio of octane (an 8 carbon chain molecule that burns slowly and requires higher temperature and pressure to ignite) and heptane (a 7 carbon chain that is more unstable, and tends to explode rather than burn, and it does so at lower temperatures and pressures). Higher octane means a fuel that burns slower, and is less likely to detonate prior to the spark plug firing. Running low octane fuel, in an engine that does not require premium, will actually make slightly more power (in the neighborhood of 1% or so) because the flame front moves faster, and is the equivalent of slightly advanced ignition timing. In an engine with high compression or a turbo that requires high octane fuel, running 87 will cause ping or detonation, and the engines knock sensor will pick that up, and retard timing or enrich the fuel mix, both of which reduce power and performance. Using the fuel the manufacturer recommends will give you the best mileage, though as always, your mileage may vary and driving habits and overall engine and car condition and maintenance make a much larger difference in fuel mileage than brand or octane rating.
Thanks!

Here's what the owner's manual says:

"Volvo recommends premium fuel for best performance, but using 87 octane or above will not affect engine reliability." pp258, 2013 S60 Owners Manual (Web Edition)
 

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Thanks!

Here's what the owner's manual says:

"Volvo recommends premium fuel for best performance, but using 87 octane or above will not affect engine reliability." pp258, 2013 S60 Owners Manual (Web Edition)
So, in other words, premium fuel makes the engine quieter and more powerful. Though, their electronic systems can help negate the low-end fuel.
 

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So, in other words, premium fuel makes the engine quieter and more powerful. Though, their electronic systems can help negate the low-end fuel.
Why would the engine be quieter...?

People have noted that Premium delivers better mileage so take it how you will. I use premium because it's only 8 cents/litre more at Costco.
 

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Discussion Starter · #6 ·
So, in other words, premium fuel makes the engine quieter and more powerful. Though, their electronic systems can help negate the low-end fuel.
Quieter/smoother running, yes. More powerful? Maybe. While it seems perfectly logical to expect an increase in power output from the engine with higher octane, the engine management computer may be limiting the HP and torque output.

It certainly feels like the engine is running very near the detonation point with lower octane, carefully controlled by the EMS to avoid or mitigate any actual detonation. With higher octane fuels, detonation is pretty much avoided entirely, and the engine runs smoother and quieter the farther away it is from detonation.
 

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I've always used Premium in my turbocharged Volvos. I don't know about quieter or more powerful, but it just makes sense to me to use the best fuel possible for a turbocharged engine with 300+ HP. Maybe it's the "placebo effect", but it's worth to me!
 

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This was a recent interesting report on this (including fuel efficiency testing):

http://www.cbc.ca/marketplace/episodes/2012/11/pumpfiction.html
Chevrolet Cruze 1.4L Turbo needs premium to perform at its best. Otherwise fuel economy and power will take a significant hit. And by significant, I mean significant. Inside Line observed notorious power loss and drop in fuel economy, and they love to run Regular unless absolutely required.

http://blogs.insideline.com/roadtests/PastVehicles/2011-chevrolet-cruze-ltz/
http://blogs.insideline.com/roadtes...ot-weather-mpg-test---regular-vs-premium.html
 

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I've tried 87 for two tanks and really couldn't notice much of a difference. It may have been slightly louder ... maybe ... but that's the only possible effect the lower octane seemed to have. I noticed no difference in fuel mileage or performance. I do run 91 regularly.
 

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Discussion Starter · #11 ·
I've tried 87 for two tanks and really couldn't notice much of a difference. It may have been slightly louder ... maybe ... but that's the only possible effect the lower octane seemed to have. I noticed no difference in fuel mileage or performance. I do run 91 regularly.
Hey, Stan, Thanks!

I can't help but ask - if you see no difference in fuel mileage or performance, why the extra expenditure on 91?
 

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Chevrolet Cruze 1.4L Turbo needs premium to perform at its best. Otherwise fuel economy and power will take a significant hit. And by significant, I mean significant. Inside Line observed notorious power loss and drop in fuel economy, and they love to run Regular unless absolutely required.

http://blogs.insideline.com/roadtests/PastVehicles/2011-chevrolet-cruze-ltz/
http://blogs.insideline.com/roadtes...ot-weather-mpg-test---regular-vs-premium.html
Since we also own a Cruze, I can speak to this issue. I noticed NO difference whatsoever between 87 and 91 in our Cruze. However, we don't get the weather Phoenix does. GM tunes their cars more conservatively.

Has anyone attempted to quantify the fuel consumption difference between 87 and 91 for the T5 and T6? My driving habits are so erratic I could not begin to make a comparison
 

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Hey, Stan, Thanks!

I can't help but ask - if you see no difference in fuel mileage or performance, why the extra expenditure on 91?
It's more psychological than anything else. I know the car's maximum performance is with 91+ so, even though I can't really feel the difference, I do it anyway.

My last car was an Audi A4 4 cylinder turbo, and it also called for 91 octane. I almost never ran that on anything but 87, but it was leased not owned, so I somehow felt that was okay. My 2009 Corvette calls for 91, and I have tried 87 on that as well. No perceived difference in anything there either, but I almost got my car confiscated when I mentioned that on a Corvette forum. :)
 

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I had used multiple consecutive tanks of 87 (which may have 10% ethanol) to see if there is any difference with my driving habits.
One thing that did stand out with the 87 is with cold starts. The engine would start, go to high idle, and then surge or hunt for an RPM. It would be about a 2-300 rpm fluctuation for about 30 seconds.
This went away after the switch back to 91.
I mentioned it to the dealer but they were kind of hands off about it.
 

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Chevrolet Cruze 1.4L Turbo needs premium to perform at its best. Otherwise fuel economy and power will take a significant hit. And by significant, I mean significant. Inside Line observed notorious power loss and drop in fuel economy, and they love to run Regular unless absolutely required.

http://blogs.insideline.com/roadtests/PastVehicles/2011-chevrolet-cruze-ltz/
http://blogs.insideline.com/roadtes...ot-weather-mpg-test---regular-vs-premium.html
You need premium fuel for a 20K car producing less than 150 HP..... :rolleyes::facepalm: Aaaaaaaaaaaand, that's why I'm definitely NOT a GM (pronounced "Government Motors") fan.
 

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Discussion Starter · #16 ·
It's more psychological than anything else. I know the car's maximum performance is with 91+ so, even though I can't really feel the difference, I do it anyway.

My last car was an Audi A4 4 cylinder turbo, and it also called for 91 octane. I almost never ran that on anything but 87, but it was leased not owned, so I somehow felt that was okay. My 2009 Corvette calls for 91, and I have tried 87 on that as well. No perceived difference in anything there either, but I almost got my car confiscated when I mentioned that on a Corvette forum. :)
I had a 2002 C5 Corvette Coupe that for 11 years never got anything but 91 or 93 when I could get it. and, despite assurances that it would run just fine on 87, I simply couldn't do it. (I hope it doesn't carry over to the S60 - it does seem to run extremely well on 91 and I tend to listen to what the car is telling me, even if it costs more at the pump.)
 

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My T5 just under 30K miles has always used "regular", 87 octane and is very happy. Plenty of power - always there when I need it, especially in Sport Mode. (Yahoo). Just returned from a 2- day, 500 mile trip and got 30 mpg on calculator (32 mpg according to Sensus computer). And by the way, I love this car, especially on a trip.
 

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I figure the difference between putting in 93 and 87 octane costs me less than $200 a year.

Why even think about it?
 

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I had to put 87 (Regular) in my RD back during Hurricane Sandy because that was all I could find for roughly two fill up's and my MPG's and overall performance took a noticeable hit. There is actually a little blue Polestar sticker on the fuel door that "Recommends Premium Fuel."
 

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With my 850 T5-R and 2.5T cars, there was a somewhat noticeable difference. With the 2.4T, I noticed nothing. It wasn't something I could feel, but when I went to pass I would notice the power wasn't always there like I expected it to be. Holy crap, my x key is working today. Party at my place.
 
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