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Recent trip to Chicago. Headed back tomorrow or Friday. Will report mileage on return trip. I hand calculated 29.4 when it read 30.0 on the computer.

Sent while in DEFCON Brown.
 

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I've noticed the same thing the closer to 80mph the better the mileage until after 80 then it goes down...it's funny cruising at 60 is more of a killer than cruising at 76-78mph mileage wise.
 

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yeah URO_S60 is right, ~75 on my R I've noticed is the sweet spot in 6th, unless I am going 60 where it's totally flat.
 

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Yep - I tend to agree with "URO" -

My guess is that when in 6th, the geartrain is too "tall" for continuous cruising on average highways with gradual rolling hills.
(This may be different on flat roads in the Plains, but our highways are not like that around here.)
If you're going about 60, it seems to want to be in 5th for the ascents and 6th for the descents - otherwise, it "grunts" a bit too hard uphill and mileage suffers.

In the mid-70's (MPH), the engine RPMs are high enough to overcome the uphill "bogging".
 

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I really with 6th gear at 75MPH was more like 1200RPM instead of 2800RPM. Volvo should have made 6th super tall for better mileage.
 

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I really with 6th gear at 75MPH was more like 1200RPM instead of 2800RPM. Volvo should have made 6th super tall for better mileage.
not me, if they had it any taller we'd need to go 85 for max. fuel efficiency. until the speed limits change I'm not doing 85 all over. any fuel savings would go towards tickets... around here u can't go 85 without getting noticed.
 

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When I was in Ok. 75mph highways were perfect (yes I may only have the 5speed GT) but cruise control on them long flat roads at 75-78mph and you could see 450+miles on a full tank of 91oct. From OK. to Ma. I stopped like 5 times to refuel (from 1/4 tank) to cover 1850miles it's about 460miles/tank. Which I think is great, however the opposite side of the coin city driving can become a killer in traffic and constant stop/go roads.
 

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One day I reset the computers average mpg stat and babied the crap out of it for an hour drive mostly 55mph and only a couple redlights. I took a picture but I think the average was 36.9

If no one will believe me I'll find the picture, it was in July so it's not in my phone anymore..
 

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One day I reset the computers average mpg stat and babied the crap out of it for an hour drive mostly 55mph and only a couple redlights. I took a picture but I think the average was 36.9

If no one will believe me I'll find the picture, it was in July so it's not in my phone anymore..
I don't believe you. Now is that because I don't or because I just want you to waste your time finding a picture?

seriously though that is about right. I was hitting 34-38 going 55-60 with no hills what so ever. i assumed i was getting around 35 but didn't calculate by hand because honestly I really didn't care that much. I didn't buy it for fuel economy even though it is impressive what you can get on the hwy when staying out of boost.
 

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Wow my avg. mileage has never been more than 14.2. It's at 13.9 now. Im rarely on hwy and usually drive like an @ss tho.
 

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Im rarely on hwy and usually drive like an @ss tho.

there's your answer fishbulb.

city mileage is dreadful.
 

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it's achievable. I used to avg 24-25mpg highway could never get it above that until I changed my driving habits!

Here's my max:

 

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not me, if they had it any taller we'd need to go 85 for max. fuel efficiency. until the speed limits change I'm not doing 85 all over. any fuel savings would go towards tickets... around here u can't go 85 without getting noticed.
Here in Tampa in the rush hour commutes I-75 cruises between 70 and 90 normally. I think I average about 80mph.
 

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Ive gotten 500 mile tanks more than a few times cruising between Colorado and either Utah or South Dakota (my personal best is a 540 mile tank that took 17.9 gallons when I filled up).......I have noticed that the fuel economy estimation gets worse the better mileage it shows. For example, around town, my estimation is typically +1 mpg over actual mpg. During road trips, it is not uncommon to see an estimation that is +3 to 4 mpg above actual.

It seems my sweet spot is right around 27-2900 RPM, which translates to ~75 mph

Has anyone else compared the estimation error and found similar errors as me?
 

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75 mph is my R's sweet spot, too. It makes about 30 mpg, which I have calculated thrice to verify. It's the same trip that realizes this mpg -- from Blue Diamond Blvd near Las Vegas to Carson St. in Long Beach. One would suspect this, given the descent from high desert to sea level and a cruise at 75 for nearly the whole 265 miles. On the way from LGB to LAS, mpg is lower, around 26, still better than my usual 22.5 mpg in mixed driving.
 
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