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I track fuel economy in my cars with an old Palm application (automobile by linkesoft.com). I've always noticed a definite seasonal fuel economy change in my Volvos, or at least, our former 850 NA and current XC90 2.5T.<p>Funny thing is, my V50 T5 is steady as a rock, seasonally. It doesn't seem to respond much to temperature or fuel formula. Now, it has a different fuel management system in the Bosch Motronic ME9 (vs ME7 in the XC90), but this really surprises me.<p> <IMG SRC="http://users.rcn.com/tmtalpey/V50/38934.jpg" BORDER="0"> <IMG SRC="http://users.rcn.com/tmtalpey/V50/38949.jpg" BORDER="0"> <p>As you can see, we've had the XC90 and V50 for about the same time, and although the XC90 has ~57K miles to the V50's ~43K, after the break-in period these graphs are completely different.<p>I don't have a good explanation for this yet, but it sure is interesting. Anyone else have a similar experience - or different one? Does the 2.4i behave differently, for example?<p>Tom.
 

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Discussion Starter · #3 ·
Re: (S40DaB)

Unfortunately, 28mpg is the top of the graph. The green overall average line at the center is about 22.5mpg. Mine is AWD, which costs a few mpg due to lower final drive gearing, and I don't baby it either.<p>Tom.
 

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Re: Seasonal mileage (non-) variation (tmtalpey)

Do you change your tires in the winter?<br>Maybe it has something to do with wheel slip.
 

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Re: Seasonal mileage (x-omatic)

2.4i 5MT, summer tires year round. I have been tracking fuel economy as well. With the stock intake system over a 1 year period, I see 26.8mpg(with significant deviation) in the winter months(October-March) and 28.4(relatively stable) avg in the summer months(April-September) however I have seen highs of 34.5mpg in the summer and lows of 21.6mpg in the winter
 

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Re: Seasonal mileage (x-omatic)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>x-omatic</b> »</i></TD></TR><TR><TD CLASS="quote">Do you change your tires in the winter?<br>Maybe it has something to do with wheel slip.</TD></TR></TABLE><br>No, in fact the XC90 has Nokian all-seasons year 'round while the V50 goes from summer to winter shoes in November and back in March. And it's just not snowy enough around here to account for such a sharp and steady seasonal trend, on the wheel slip theory.<p>Both cars get a steady diet of Mobil Super (93 AKI) btw.<p>Say, I've got local degree-days plotted on a heating usage spreadsheet, maybe I can put it on the same axis...<p>Tom.
 

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Re: Seasonal mileage (tmtalpey)

Dont forget this:<br><A HREF="http://www.slate.com/id/2098672" TARGET="_blank">http://www.slate.com/id/2098672</A>/
 

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Re: Seasonal mileage (sanatarium)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>sanatarium</b> »</i></TD></TR><TR><TD CLASS="quote">2.4i 5MT, summer tires year round. I have been tracking fuel economy as well. With the stock intake system over a 1 year period, I see 26.8mpg(with significant deviation) in the winter months(October-March) and 28.4(relatively stable) avg in the summer months(April-September) however I have seen highs of 34.5mpg in the summer and lows of 21.6mpg in the winter</TD></TR></TABLE><p>That might be because of the much higher ethanol mix in the summers. They have a special bend out here because of the heat.
 

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Re: Seasonal mileage (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"><br>No, in fact the XC90 has Nokian all-seasons year 'round while the V50 goes from summer to winter shoes in November and back in March. And it's just not snowy enough around here to account for such a sharp and steady seasonal trend, on the wheel slip theory.<p>Both cars get a steady diet of Mobil Super (93 AKI) btw.<p>Say, I've got local degree-days plotted on a heating usage spreadsheet, maybe I can put it on the same axis...<p>Tom.</TD></TR></TABLE><p>How long do you let your car warm up in winter?
 

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Re: Seasonal mileage (sanatarium)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>sanatarium</b> »</i></TD></TR><TR><TD CLASS="quote">Dont forget this:<br><A HREF="http://www.slate.com/id/2098672" TARGET="_blank">http://www.slate.com/id/2098672</A>/</TD></TR></TABLE><br>(Summer blend gas info).<p>Sure, that was always my explanation for the seasonal change in my previous Volvos.<p>My question is, why <b>doesn't</b> it change the V50?<p>Tom.
 

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Discussion Starter · #11 ·
Re: Seasonal mileage (x-omatic)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>x-omatic</b> »</i></TD></TR><TR><TD CLASS="quote">How long do you let your car warm up in winter? </TD></TR></TABLE><br>Same in all climate. I let it run for a few seconds until the engine "sounds" right, i.e. the oil is fully distributed. In extremely cold weather, i.e. sub-zero mornings once or twice a year, I'll let it run for 20-30 seconds with the clutch engaged until the tranny input shaft stops complaining. Note to self, probably time to check/change the M66 trans oil.<p>Next idea?<p>Tom.
 

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Re: Seasonal mileage (tmtalpey)

Certainly peculiar. The 2.4i definitely varies, perhaps this is T5 related? Any other T5 owners tracking mileage?
 

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Re: Seasonal mileage (sanatarium)

I've tracked MPG since day #1 but I don't have it charted, almost 100,000 miles worth over three years. But scanning the log book shows winter MPG about 1-1/2 to 2 MPG less than summer. Almost all miles were the same 60 mile one-way daily commute. <p> TOM - Nice to see You posting again. But You always told Me the 6-spd manual didn;t need the lube changed.... <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/tongue.gif" BORDER="0"> <p> Anyhow, What do You recommend for fluid?
 

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In my 2 months of ownership I've been at a consistent 27-27.5 mpg...T5 engine. Not too long term, but to give some numbers.
 

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Re: Seasonal mileage (non-) variation (tmtalpey)

I have had my T5 AWD for about a year now and notice a distinct difference. 23mpg average for winter months and 27mpg for summer. <p>I run dedicated winter tires and it can get as low as -15 F for a couple of weeks in a row.
 

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Discussion Starter · #16 ·
Re: Seasonal mileage (POWERSTROKE)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>POWERSTROKE</b> »</i></TD></TR><TR><TD CLASS="quote"> You always told Me the 6-spd manual didn;t need the lube changed.... </TD></TR></TABLE><br>Doesn't need it as a routine thing. If it makes noise, starts acting funny, etc that's a different story. Mine's not quite there, but (for example) the other day I was coming down a parking garage ramp in neutral, the trans was cold and making this sort of cackle. Pressed clutch, no noise. Released clutch, noise. <p>As for fluid choice, factory. My indy (veteran SCCA'er) will recommend something else of course. Some kind of Motul concoction I'm sure. Haven't really thought about it much yet.<p>As for 27+mpg, grrr. That's the peak I've <i>ever</i> gotten.<p>Tom.
 

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Re: Seasonal mileage (tmtalpey)

Hi Tom,<p><A HREF="http://www.epa.gov/oms/rfgecon.htm" TARGET="_blank">Here</A> is some information about the differences in energy content between summer and winter blends for conventional and RFG (reformulated gasoline).<p>It is not much, on the order of 1.5-2.0%, maybe a little more if blending variations are taken into account.<p>If we assume it's 2% (the math is convenient), you will be looking for a difference of 0.4-0.5 mpg, all other things being equal--which they are probably not.<p>At this level of variation, the differences may be indistinguishable.<p>Your xc90 chart average has a sinusoidal character to it--interesting.<p>I wonder what this data would look like if it was normalized for average daily temperature.<p>Peter
 
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