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Discussion Starter · #1 ·
On a typical trip between Seattle and Portland, I'll usually go around 7-8 MPH faster than the speed limit, though I'll go even faster in locations where I know the WSP have no place to hide. And I typically get less than 25 MPG on those trips.

Today I wasn't in a big hurry, so I decided to travel at the speed limit. I used the cruise control when not in dense traffic, setting it at about 61 MPH in 60 zones and about 71 MPH in 70 zones. I was surprised that I was seldom passed. When at ~60 MPH, I averaged 29.8 MPG. When at ~70 MPH, I saw instantaneous MPG hovering around 25 MPG. Overall mileage for the trip (based on the Volvo's trip computer, reset when I began my trip this morning) was 27.9 MPG over 189 miles, including one gas stop and a little traffic in downtown Seattle and downtown Portland.

The best I've ever gotten before was 25.2 MPG, so slowing down around 10 MPH on average did have a noticeable effect on fuel economy. Just like I'd expect, and like the people on the news have been saying. Not that I'll be able to stand to drive the R so conservatively very often.

As an aside, I was happy to find Shell V-Power (92 octane) for $3.239 in Vancouver, WA on my way, as 87 octane has been almost that much in Seattle, with premium ~$0.20 more.
 

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Re: What do you know... speed really does affect MPG! (sgmlaw)

Quote, originally posted by sgmlaw »
Over a dollar a mile . . . still a better value than most other amusement rides.

Priceless actually...
 

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Re: What do you know... speed really does affect MPG! (kr900)

oh yea... if you exercise self-control you can really get good gas MPG on this car. I averaged 27 mpg from SF to LA once.

But most of us won't, precise the reason why we buy the R.
 

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Re: What do you know... speed really does affect MPG! (kr900)

From my autobahn testing last year. Level ground, once cruising, setting cruise control and then resetting avg mpg and driving for about a mile. 9 mpg drop 60-90 mph, only 5 mpg drop, 90-120 mph.

mph-- mpg
60 ---- 29
70 ---- 27
80 ---- 23
90 ---- 20
100--- 18
110--- 16
120--- 15
130--- 14
 

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I get 34 easily on my almost weekly trips to augusta and atlanta in my R and this is with the cruise set at 72. I don't know if my mods have anything to do with it... but I have always gotten over 30 on the highway when I am driving like a civilized person.
 

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Re: (R_Rated)

Quote, originally posted by R_Rated »
I get 34 easily on my almost weekly trips to augusta and atlanta in my R and this is with the cruise set at 72. I don't know if my mods have anything to do with it... but I have always gotten over 30 on the highway when I am driving like a civilized person.

How are you calculating this? It sounds highly improbable.
 

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Re: (Dashdog)

Quote, originally posted by Dashdog »


How are you calculating this? It sounds highly improbable.

Take what your Volvo trip computer tells you with a grain of salt. My R so far is pretty close but my XC90 has been way off.

I track my fuel purchased against Km's travelled in a spreadsheet, for my R it's been pretty close: 17.1L/100km on the trip computer vs. 17.8L/100Km from the actuals on my spreadsheet. My XC90's trip computer shows 19.1L/100Km when my actuals show 18.1.

Anyone else compare actuals to the trip computer in their R, or know exactly how the program in the Volvo trip computer makes its calculations?

Quote, originally posted by stevectsai »
oh yea... if you exercise self-control you can really get good gas MPG on this car. I averaged 27 mpg from SF to LA once.

But most of us won't, precise the reason why we buy the R.

You hit it right on! I don't know why bother tracking it so closely when both of my Volvo were not purchased with fuel economy in mind


LTA
 

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Re: (LTA)

Quote, originally posted by LTA »

Anyone else compare actuals to the trip computer in their R, or know exactly how the program in the Volvo trip computer makes its calculations?
LTA

I read somewhere that the computer calculates the duty cycle of the fuel injectors.
I used to check during fill-up and it's been accurate to within .5mpg. and yes I do reset the counter after each fill-up.
 

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Re: (LTA)

Quote, originally posted by LTA »


Take what your Volvo trip computer tells you with a grain of salt. My R so far is pretty close but my XC90 has been way off.

I track my fuel purchased against Km's travelled in a spreadsheet, for my R it's been pretty close: 17.1L/100km on the trip computer vs. 17.8L/100Km from the actuals on my spreadsheet. My XC90's trip computer shows 19.1L/100Km when my actuals show 18.1.

Anyone else compare actuals to the trip computer in their R, or know exactly how the program in the Volvo trip computer makes its calculations

LTA

You should see my average mpg after a couple of days out at the track. Last time it took me 4 hours to get the miles to empty to stop saying 120 miles after a full tank of gas. Believe me, I hit the reset botton a few times on the way home.

I keep the reciepts and work off that. The trip computer only averages out the last tank of gas and tries to calcutate that to the next tank. It's always off. Even if you reset it. You're probably better off telling you what you had in fuel econemy on the last tank when you fill up and roll the dial to miles to empty.
 

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Re: (LTA)

Quote, originally posted by LTA »


Take what your Volvo trip computer tells you with a grain of salt. My R so far is pretty close but my XC90 has been way off.

I track my fuel purchased against Km's travelled in a spreadsheet, for my R it's been pretty close: 17.1L/100km on the trip computer vs. 17.8L/100Km from the actuals on my spreadsheet. My XC90's trip computer shows 19.1L/100Km when my actuals show 18.1.

Anyone else compare actuals to the trip computer in their R, or know exactly how the program in the Volvo trip computer makes its calculations?

You hit it right on! I don't know why bother tracking it so closely when both of my Volvo were not purchased with fuel economy in mind


LTA
Hmm, interesting. I agree with the orginal point of the post, slower generally results in less fuel cosumption. FWIW, here are some states on a recent survey with my R which has 18,000 miles on it (all survey driving above 5200 feet with most above 6500 ft - if it makes a difference). This driving was all done in cold to cool temps. 90% highway, 10% city. For this survey my highway speeds tend to be just above 75 mph speed limit with some runs to significantly higher mph's. Pretty easy on the accleration in town. Averages for 1519 miles, 50 mph, 24.1 mpg. Next time I will track the actual fuel purchases and compare to computer for average fuel consumption.
 

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Re: (Dashdog)

Quote, originally posted by Dashdog »


How are you calculating this? It sounds highly improbable.
I go by the computer and then do the math when I fill up.

example: 300 miles/10gallons = 30 miles a gallon

this only works when you push the button last time you had a full tank. Most people prolly already know how to do this but you would be amazed at the people that never thought of it.
 

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I, too, find 34mpg high improbable, especially at 72mph. I could see it happening on level ground in 6th gear traveling 45mph
 

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Re: (phuz)

According to the onboard computer, I did pull over 30 MPG, but only once, going at a "brisk" speed on the PA turnpike last year. This was a steady cruise with no acceleration, on a straight and level roadway, over about 55-60 miles, during cool and calm evening weather. "Brisk" was a number with an 8 somewhere in it. But that's all I'll say, as I never speed.


The car is indeed capable of over 30 MPG at higher speeds. But that is quite the exception and only when everything is going right. The low 20's is more the norm in any sort of traffic.
 

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Discussion Starter · #16 ·
Re: What do you know... speed really does affect MPG! (stevectsai)

Quote, originally posted by stevectsai »
oh yea... if you exercise self-control you can really get good gas MPG on this car. I averaged 27 mpg from SF to LA once.

But most of us won't, precise the reason why we buy the R.

My thoughts exactly. It was a good exercise to see what kind of fuel economy I could get, but I haven't got the self-control to drive so responsibly on a regular basis...
 
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