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Discussion Starter #1
I am beginning to mistrust my average MPG-ometer. All my journeys start with 20-40 minutes threading out through the City (and this is London, not somewhere with rational high speed links...), and then it's motorway/freeway - I don't commute in this car.

What makes me not trust the machine is this: I can just about crack 30mpg if I stick rigidly to 70mph, which kind of makes sense if I'm getting 35-ish at a cruise and a hell of a lot less while getting out of town. But! If I pull in and tank up while on the long-haul roads then the first hour will report a DROP in MPG. Now, unless getting back up to cruise is done at about 0.5mpg, this has to be mad.

Doesn't it?

Should I expect to be able to get up into the mid-30's on a long run?
 

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BenzWorld Elitist
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You have to take the MPG readings with a grain of salt. Mine have been a bit optimistic. Readers also please note that LT is discussing UK mileage which involves imperial gallons.

I normally get 27-28mpg on highway trips (someone else will have to do the conversion). Not sure what your question is exactly, because stopping to fill up will most definitely reduce your overall mileage noticeably. Hell, just giving it some gas to get around someone will do that. My best run ever (30.0mpg over 100 miles) involved virtually no acceleration the whole way! Under hard acceleration you are getting around 4-5mpg imho.

Still, on a long journey, the small amount of acceleration back up to highway speed should get factored in and represent a relatively minimal effect overall.
 

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Discussion Starter #4
I have made a 200 mile trip and never got above 24mpg. But who buys these cars for mpg?
well, me! I make thousand-mile trips four or five times a year, sometimes more often. While there's always the odd burst to 150, and alpine pass to climb: it's nice to get an efficient run in places where you just can't go fast. The Subaru went to Switzerland last summer and did 35mpg. My old E55 would just nudge 30 on the same run, because quite long stretches of it are 120-130km limits, two-lane, and full of trucks.

It makes sense to me that a 7 speed car at a very steady cruise should return good figures, if it's in good shape and well designed.
 

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On my 180 mile treks to Milwuakee I notice the mpg improving as I get above a 65 mph average. I usually get over 28 mpg at that speed. The best was 29.4 and the worst was 27.6. That's better than my E320 4Matic or E420 got.
 
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