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Discussion Starter · #1 ·
Do you use premium or regular unleaded? And have you noticed much of a difference in your average MPG?
 

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Re: Fuel usuage question... (neranima)

87 octane regular, 37K miles. summer 19 - 25 mpg, winter 16.5 - 22mpg depending on types of driving. 2.5T awd. The winter fuel formulation knocks the fuel efficiency way down. This car likes it hot with summer fuel.
 

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Re: Fuel usuage question... (neranima)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>neranima</b> »</i></TD></TR><TR><TD CLASS="quote">Do you use premium or regular unleaded? And have you noticed much of a difference in your average MPG? </TD></TR></TABLE><p>We just completed a 1,000 mile comparison. Normal driving, but we watched the mileage over 1,000 miles. At near $3/gallon prices and $0.20 difference between 87 and 92, it was slightly more economical for us to use the premium, IF we could keep from tromping the accelerator pedal.<p>It's close enough to being the same cost/mile that we use the premium. <p>Jack
 

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Re: Fuel usuage question... (neranima)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>neranima</b> »</i></TD></TR><TR><TD CLASS="quote">Do you use premium or regular unleaded? And have you noticed much of a difference in your average MPG? </TD></TR></TABLE><br>Over 60,000 miles my records show that I get roughly 0.5 mpg better with Plus than Regular and another 0.5 with Premium. (That does not include towing miles which drops mpg by about 4.) I calculate that Regular is slightly cheaper overall. <p>Driving conservatively I feel no difference in performance. I would guess that driving aggressively would provide a better case for Premium. Because so few people buy Premium these days I sometimes wonder how long the fuel has been sitting in the service station tank.
 

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Discussion Starter · #5 ·
Thanks for the feedback... definitely good info. I'm going to have to fuel up and test it out to see if the difference is beneficial for me and my driving style....
 

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Re: Fuel usuage question... (XC-Ski)

Octane does not scientifically correlate with fuel economy. Read about it on the internet. It relates to engine knocking. Most newer engines adjust automatically to different octane levels.<p>37,500 miles 2.5T burning 87 octane, never heard a single knock, engine is quite peppy and performs well. Use synthetic oil change it frequently and keep your tranny fluid changed you'll get more bang for you $.
 

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Re: Fuel usuage question... (myxc90)

The engine has an active timing scheme that listens for knock and adjusts timing and boost (if turboed) accordingly. Running premium allows the engine to operate in a more efficient range and will produce slightly better mileage but not 20 cents/gallon better.
 

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Re: Fuel usuage question... (Aztecian)

20 cents per gallon out of three bucks is about 6%. Our car gets that and more (we run 93). Besides, it runs so much better.<p>Tom.
 

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Re: Fuel usuage question... (tmtalpey)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>tmtalpey</b> »</i></TD></TR><TR><TD CLASS="quote">20 cents.</TD></TR></TABLE><p>Premium I pay for Sunoco 94 is over 60 cents around here. After listening to late model Mercs ping as they pull away, starting to pay more attention to this:<br><A HREF="http://www.toptiergas.com/index.html" TARGET="_blank">http://www.toptiergas.com/index.html</A><p><I>As a postscript, other reasons I use 94 is watching catalytic converters in the past bite it from high fuel sulfur content and avoiding the not emissions component friendly additive MMT.</I><BR><BR>
<i>Modified by Tao at 7:55 AM 9-5-2006</i>
 

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Discussion Starter · #10 ·
OK, so I ended up putting in premium, for a full tank which came to roughly $45, since gas somewhat came down in price. So far, I notice that I have more kick and end up doing a higher instantaneous MPG when cruising, so this is a good sign, however due to the change of my driving method lately, I've been averaging a lower MPG. So I'll invest once again in premium and I believe that I'll be able to get a better average... we'll see.
 

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Re: (neranima)

in 100 degree weather or more, it would be better to use low octane fuel to extend the life of the ceramic oxygen sensors and reduce engine heat. ...don't know if that applies to where you live. vice-versa, on the winter use premium for better fuel ignition. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/embeer.gif" BORDER="0"> <p>
 

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Re: Fuel usuage question... (myxc90)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>myxc90</b> »</i></TD></TR><TR><TD CLASS="quote">Octane does not scientifically correlate with fuel economy. Read about it on the internet. It relates to engine knocking. Most newer engines adjust automatically to different octane levels.<p>37,500 miles 2.5T burning 87 octane, never heard a single knock, engine is quite peppy and performs well. Use synthetic oil change it frequently and keep your tranny fluid changed you'll get more bang for you $.</TD></TR></TABLE><p>OK, I'll give you that, but you're saying that adjusting the engine's timing has nothing to do with gas mileage or, more accurately, to how efficiently the engine runs?<p>Frankly, newer engines don't adjust to octane, they adjust to allow the engine to not knock.<p>If newer engines adjusted to octane levels, then older engines adjusted to octane levels too. Magic, right? Wrong. Timing was merely mechanically advanced or retarded depending on engine speed and load. It's almost like they knew what they were doing. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/rolleyes.gif" BORDER="0">
 

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Re: (crash)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>crash</b> »</i></TD></TR><TR><TD CLASS="quote">in 100 degree weather or more, it would be better to use low octane fuel to extend the life of the ceramic oxygen sensors and reduce engine heat. ...don't know if that applies to where you live. vice-versa, on the winter use premium for better fuel ignition. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/embeer.gif" BORDER="0"> </TD></TR></TABLE> <p><br>You my have that backwards. Higher octane allows more advanced timing, lower heat. Lower <br>octane burns faster (that is why it pings with advanced timing) and would ignite faster in winter. <br>Lower octane burns fast and ignites easy, higher octane burns slow is ignites less easy and is why higher compression engines demand it. <p>Engines that are designed to use higher octane will run cooler and more efficient using it, they will <br>retard the timing so they dont ping on lower octane. Even running high octane fuel the engine gets the timing advanced until it detects some pinging (you cant hear it) and then retards the timing just enough to stop the ping. This is the most efficient way to run an engine. <p>One more thing, higher octane fuels usualy have more detergents and keep injectors and other parts cleaner. Thus less money later for repairs and a more efficient engine over the long run. <p><br>Funny side note... Friend that has a truck with 300k dumps in 15 bottles of STP fuel treatment on a empty tank before a smog test. Testers always are amazed on how clean that truck runs!! After the test he fills it up with gas to dilute the stuff. He then adds the 2 quarts of oil to the crankcase that it burns every week. I woundt recommend doing the fuel treatment trick on your volvo.<br>
 

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Re: Fuel usuage question... (Beiner)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Beiner</b> »</i></TD></TR><TR><TD CLASS="quote"><p>Frankly, newer engines don't adjust to octane, they adjust to allow the engine to not knock.<br> </TD></TR></TABLE><p>A fuel's octane rating is a rating of it's ability to resist pre-detonation. This is also known as it's <B>anti-knock index, aki</B>. The higher an aki rating for an engine, the less likely it is to knock or ping. This is why diesels, wich operate solely by pre-detonation, have an octane rating of around 47. If you put gas in a diesel engine, the compresison wouldn't be able to ignite the fuel, and it wouldn't run. So engines do adjust to octane, they back off on performance by adjusting timing so that pre-detonation will not occur. I think what you are referring to is that an engine designed to run on 87 RON (research octane number) will not GENERALLY show increases in power with a higher octane, because the car is only set up to reduce timing to prevent pre-detonation, not react to a higher octane number. If you put 100 octane in, you wouldn't see a difference, because the car won't advance the timing to compensate as long as it is making it's full "design' power. <p>If a modern engine is designed to run on 91 RON (like most Volvo turbos are) the car will still run on 87 octane without pinging, because the anti-knock sensor will dial back timing to prevent it. However, by dialing back timing, you're not making the full design power. <p>Sometimes, however, an engine CAN benefit from running on higher octane than is called for in the manual, usually because manufacturers have to dumb the engine down for local fuel requirements. Case in point is the R, which runs much better on 93-94 octane than the 91 octane that is the stated requirement in the manual. This is because the engine really wants to run on higher octane European fuel than is available here. <p>Bottom line, if you use lower octane than is called for in your manual, you will see a decrease in performance and / or mileage. <p>Older cars, which Beiner pointed out have fixed timing and no knock sesnor, relied solely on the octane of the fuel that went into them to run properly. If you got a lower grade than the engine had been designed to run on (or better yet for back then, built to run on since those older engines seemed to have broad tolerances) than you had bad pinging and knock. <p>
 

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Re: Fuel usuage question... (needsdecaf)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>needsdecaf</b> »</i></TD></TR><TR><TD CLASS="quote"><p>A fuel's octane rating is a rating of it's ability to resist pre-detonation. This is also known as it's <B>anti-knock index, aki</B>. The higher an aki rating for an engine, the less likely it is to knock or ping. This is why diesels, wich operate solely by pre-detonation, have an octane rating of around 47. If you put gas in a diesel engine, the compresison wouldn't be able to ignite the fuel, and it wouldn't run. So engines do adjust to octane, they back off on performance by adjusting timing so that pre-detonation will not occur. I think what you are referring to is that an engine designed to run on 87 RON (research octane number) will not GENERALLY show increases in power with a higher octane, because the car is only set up to reduce timing to prevent pre-detonation, not react to a higher octane number. If you put 100 octane in, you wouldn't see a difference, because the car won't advance the timing to compensate as long as it is making it's full "design' power. <p>If a modern engine is designed to run on 91 RON (like most Volvo turbos are) the car will still run on 87 octane without pinging, because the anti-knock sensor will dial back timing to prevent it. However, by dialing back timing, you're not making the full design power. <p>Sometimes, however, an engine CAN benefit from running on higher octane than is called for in the manual, usually because manufacturers have to dumb the engine down for local fuel requirements. Case in point is the R, which runs much better on 93-94 octane than the 91 octane that is the stated requirement in the manual. This is because the engine really wants to run on higher octane European fuel than is available here. <p>Bottom line, if you use lower octane than is called for in your manual, you will see a decrease in performance and / or mileage. <p>Older cars, which Beiner pointed out have fixed timing and no knock sesnor, relied solely on the octane of the fuel that went into them to run properly. If you got a lower grade than the engine had been designed to run on (or better yet for back then, built to run on since those older engines seemed to have broad tolerances) than you had bad pinging and knock. <p></TD></TR></TABLE><p>Well said needsdecaf but what are you doing over here in the XC90 forum? You don't have an XC90 <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/wink.gif" BORDER="0"> <p>I'd like to add one more thing:<br>Engine knock is damaging. If you plan to keep your Turbo Volvo for a long time use premium grade fuel. Knock is not just about pre-detonation it's also about creating an even 'flame front'. Ideally you want the air/fuel mixture to burn the way the engineers designed the engine to burn it. Hot running turbo Volvos push those designs to their limits. Bottom line is if you're leasing and don't give a damn shame on you and just put in the cheapest gas you can find but if you own it and want to drive it for 10+ years use premiun/higher octane fuel.<p>LTA<br>
 

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Re: Fuel usuage question... (needsdecaf)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>needsdecaf</b> »</i></TD></TR><TR><TD CLASS="quote"><p>. This is why diesels, wich operate solely by pre-detonation, have an octane rating of around 47. If you put gas in a diesel engine, the compresison wouldn't be able to ignite the fuel, and it wouldn't run. </TD></TR></TABLE><p><br>Gas is a Octain fuel, Diesel is a Cetain fuel. They are very different. Diesel is injected at the top of the compression stroke so there isnt a chance for pre-detonation like a gas engine which has all of the air and fuel mix for the compression stroke. The reason gas will not run in a diesel is that the Cetain is not high enough, nothing to do with Octain. Gas will seriously damage diesel fuel injectors because of lack of lubrication also.<p>Back to the real point, I run high test gas in my XC90 because the engine can utilize it.
 

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Re: Fuel usuage question... (LTA)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>LTA</b> »</i></TD></TR><TR><TD CLASS="quote"><p>Well said needsdecaf but what are you doing over here in the XC90 forum? You don't have an XC90 <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/wink.gif" BORDER="0"> <p>I'd like to add one more thing:<br>Engine knock is damaging. If you plan to keep your Turbo Volvo for a long time use premium grade fuel. Knock is not just about pre-detonation it's also about creating an even 'flame front'. Ideally you want the air/fuel mixture to burn the way the engineers designed the engine to burn it. Hot running turbo Volvos push those designs to their limits. Bottom line is if you're leasing and don't give a damn shame on you and just put in the cheapest gas you can find but if you own it and want to drive it for 10+ years use premiun/higher octane fuel.<p>LTA<br></TD></TR></TABLE><p>Conversely, since the higher octane rating retards the flame front, higher octane fuels can leave more deposits in an engine. Your Volvo will not knock any more on 87 than it will on 92, due to the engine management system. This is a highly difficult question to answer; one we will not resolve on this forum. To completely answer the question you would need to factor in additives, like Ethanol and its flame front characteristics, as it can be as much as 10% of the fuel and has very different burn characteristics than petroleum.<p>FYI - we run premium in our XC90. Its right around break even on cost/mile and it's a lot more fun.<p>Jack<br>
 
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