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MPG E60 vs. E90 -- What??

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Old 01-20-2011, 08:39 AM
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We took a road trip (about 3 hours) in the 545i and I was so impressed that, with the cruise set at 73 mph, I got 30 mpg! Then the following week we took another road trip but this time we went in my wife's 2007 335i and at the same speed I couldn't get it to go over 28 mpg! So what gives? I thought the E90 should've had better mpg. Is it the twin turbos?
Old 01-20-2011, 08:50 AM
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Originally Posted by laro1965
We took a road trip (about 3 hours) in the 545i and I was so impressed that, with the cruise set at 73 mph, I got 30 mpg! Then the following week we took another road trip but this time we went in my wife's 2007 335i and at the same speed I couldn't get it to go over 28 mpg! So what gives? I thought the E90 should've had better mpg. Is it the twin turbos?

I'm not sure the turbos are doing anything at cruising speed on the highway.
Old 01-20-2011, 10:10 AM
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True (on the turbos) -- I was just thinking that the difference in the engine might make a difference.

Someone mentioned to me that it's the aerodynamics of the 5 Series. And that the valvetronic engine helps it in steady, state highway cruising.

Sounds like a deal to me!
Old 01-20-2011, 10:24 AM
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Non-turbo V8 Valvetronic engine at 73mph is pushing less revs on 6th gear than the straight 6 twin-turbo, no?

I don't believe the aerodynamic explanation too much - it's bigger, heavier and more bulky.

Still, 2MPG might be just a small calculation aberrancy. Pretty good mileage anyway. You can get over 43 on a diesel
Old 01-20-2011, 10:27 AM
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We are talking about the same course, right? Was a little unclear in your OP.

Are there gearing differences between the two cars? All things equal the lighter car should get better gas mileage, but the valvetronic system eliminates pumping losses at low throttle openings (consistent with highway driving), so who knows - anything's possible. Normalizing driving styles is also pretty hard, and it's pretty easy to dip into that 335i's power without realizing it.

That said, I've NEVER gotten 30mpg on the highway in my car on any sustained trip. Then again, I've never driven at a flat 73mph in any sustained way, either.
Old 01-20-2011, 11:00 AM
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Yes,...it was the same course, same driver, and I reset the trips when I started.

As far as the average mpg, it went between 29-30 mpg on the trip computer. I guess my thing is that I thought there would be a significant difference between the 2. I never thought that the 545i would equal it or come close to it. Now in the city,...that's a different story!
Old 01-20-2011, 11:28 AM
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See.. people shouldnt buy smaller engines... big V8s are great!
Old 01-20-2011, 02:33 PM
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What about aerodynamic difference and differences in gearing?
Old 01-21-2011, 07:06 PM
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Originally Posted by laro1965
We took a road trip (about 3 hours) in the 545i and I was so impressed that, with the cruise set at 73 mph, I got 30 mpg!
Was that 30mpg 100% interstate driving? Most of these 08 550 guys were averaging high teens to the low 20s: http://www.bimmerfest.com/forums/sho....php?p=5789463
Old 01-22-2011, 06:20 AM
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In the october 2004 BIMMER MAGAZINE the editor was amazed the 545 got 30mpg at 70mph !


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