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Discussion Starter #1
I'm pushing the forum rules; not much of a Passat B5 subject I know, but with our old '99 1.8T wagon still in limbo, I'll pass on early impressions of the economy of a B9 A5 Sportback. Rated at 34 highway, with not even 1,000 miles it was easily beating that on my commute.


A4 3.0 and A5 2.0T.jpg
A5 SB fuel consumption.JPG
 

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This is just in the beginning. My B5.5 used to give me 36MPG on cruise on highway when it was newish. The older it got the consumption went up. As of now, at 19 years old it barely gives me 27 on highway.
 

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Interesting. I suspect that the better mpg is almost all due to the transmission. The Audi is a heavier car, with similar Cd numbers as the Passat. Top gear however is .39 vs .74 - .80 in the Passat.

Emry, miles accumulated on the odo should have no effect on a maintained car's mpg. Something else must be amiss to account for your mpg drop.
 

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Emry, miles accumulated on the odo should have no effect on a maintained car's mpg. Something else must be amiss to account for your mpg drop.
Can't agree on this one. As the car and thus its mechanical/tranny ages the wear and tear accumulates resulting in sub-optimal performance compared to a new engine. As you might have noticed the older your car gets it consumes more oil.

If you have seen a Passat that is about 20 years old and still gives 35 MPG on highway let me know (I am excluding the cases where a new engine and lots of parts ave been installed).
 

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Agree, they should have no effect as long as you keep up with all fluid changes, sensor cleanings, plug changes, other regular maintenance, and not change tire size or type that attained the original mileage. Also, as years have gone by, more and more gasoline mixtures have up to 10% Ethanol which can drop mileage as well. Then there's traffic, terrain, temperature, wind, humidity....all play into getting that magic number.

From 24k to ~150k I was getting consistently the same mileage with auto trans. Then manual swap got me an extra 3-4 mpg in all conditions. The only time mileage dropped was when I had old plugs, dirty or failing sensors, or old fluids.
 

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Well, let the debate begin.

My 1998 V6 GLS FWD still gets me 29-30 MPG's all day long on the breezeway.
If you know my back story, yes the original engine was swapped out, however the engine that was swapped in had more miles than the original engine did. This 'swapped' engine has had the CCT's replaced and that's it. No other internal work has ever been done. Transmission has never been opened up. I'm well over 160k miles.
Worth noting, the original motor got the same MPG's also.
Either way, that's higher than the original 18/26 mpg - 21 combined mpg rating.
Get's even better if use better gas. I've gotten up to 34MPG's with 91 octane going between Phoenix and Burbank.
 

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Then there's traffic, terrain, temperature, wind, humidity....all play into getting that magic number.
Ylwagon picture and post referred to MPG he got on highway. As I said before, I like to know if someone with a 20 years old car and high mileage still gets 35+ MPG on highway (not like around 30 which is nominal). If you wan to consider other factors like city and traffic and wind etc then there would be a wide range of MPG readings. Actually, getting those high MPG on highway also directly depends on the weight of the load and wind effect.

What is still unlcear from the picture is whether he got that 39.9 MPG on a long range or with a short distance.
 

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Given he said it was commute, I am thinking less than 100 miles each way.

We will have to agree to disagree.

I say traffic is still a deciding factor on the highway. I live in the most densely populated corridor of the US. Highway here is not the same as highway in the middle of MI or another sparsely populated flat area. Even light traffic has a way of screwing up my numbers. Going from 70-60-65-55-70, etc takes a toll. That said, I regularly got 32ish hwy with my auto. Still get 34mpg hwy now with the tach screaming at 3k RPMs at about 65-70 with a manual.
 

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I respect everyone's opinions but honestly, the only wear-related mpg killer that I can think of is engine blow-by. That would translate to robbing the piston of some of the power from the explosive force in the cylinders, thereby deriving less propulsion from the same amount of fuel. I would think the blow-by would have to be pretty bad.

Do engines normally run richer with age? I would think that is normally remedied by the ECU making adjustments and or new injectors?

Do aging cats or turbos decrease mpg?
 

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Discussion Starter #10 (Edited)
Ylwagon picture and post referred to MPG he got on highway...What is still unlcear from the picture is whether he got that 39.9 MPG on a long range or with a short distance.
Yes I should have been specific about that. My commute is 45 miles, about 40 being straight and level freeway, typically without much traffic. The other 5 miles is side-roads to and from the freeway ramps. That 39.9 was one trip average from leaving work, until arriving home. All other days have been somewhat less than that.

This A5 has a 7-speed dual-clutch trans, which is said to be equal or superior to the usual manual gearboxes, as far as drag goes. I didn't know much about them, but these things are really interesting; basically two independent four-speeds of the typical manual trans layout, with syncros and shifting forks. One trans is designed for gears 1, 3, 5, and 7, while the other does gears 2, 4, 6, and reverse. The engine drives a multi-plate clutch unit at the front, which has two clutch sets, only one of which can be engaged at a time. Each of these clutches drives one of the "transmissions" at a time, and the clutch unit can switch between the two clutches in milliseconds. This allows the shifts to be as fast as a sportbike's, although the standard setting is set for smoother shifts. Since there is no torque converter, there isn't much fluid inside, and no cooler necessary (I think).
 

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The newer technology really improved the MPG. Even the Tiguan, which has a higher CD than my wagon, will get over 30mpg at 80mph. It runs about 2200rpm at 80 with the 8sp. With my 6sp, I get closer to 25mpg and with the V6/tip it was dropped to 22. The new 7sp DSG picked up a couple of mpg over the old 6sp one.
 

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Yes I should have been specific about that. My commute is 45 miles, about 40 being straight and level freeway, typically without much traffic. The other 5 miles is side-roads to and from the freeway ramps. That 39.9 was one trip average from leaving work, until arriving home. All other days have been somewhat less than that.

This A5 has a 7-speed dual-clutch trans, which is said to be equal or superior to the usual manual gearboxes, as far as drag goes. I didn't know much about them, but these things are really interesting; basically two independent four-speeds of the typical manual trans layout, with syncros and shifting forks. One trans is designed for gears 1, 3, 5, and 7, while the other does gears 2, 4, 6, and reverse. The engine drives a multi-plate clutch unit at the front, which has two clutch sets, only one of which can be engaged at a time. Each of these clutches drives one of the "transmissions" at a time, and the clutch unit can switch between the two clutches in milliseconds. This allows the shifts to be as fast as a sportbike's, although the standard setting is set for smoother shifts. Since there is no torque converter, there isn't much fluid inside, and no cooler necessary (I think).
Correct, except you can still view it as one trans but 2 clutches. One will release from 1st at the same time the other clutch is engaging 2nd and so on. VW calls it the DSG. I had the 6 spd DSG in my 2013 CC. Loved it. super fast. I got 38mpg on one tank to Asheville, NC one time. something like 530 miles.
 

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OK I must admit I had not factored in the dual clutch transmission technology because those 8 speeds really matter. Also the lack of torque converter is a good candidate to lower MPG.
 

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OK I must admit I had not factored in the dual clutch transmission technology because those 8 speeds really matter. Also the lack of torque converter is a good candidate to lower MPG.
Most times, yes. The ZF8 auto in the B8-8.5 A4s and other models in that year range have great mileage because of it. The tq converter losses on that trans are less than almost any other traditional auto in that price range. I got 34mpg from here to NC a couple years ago in my B8.5 A4 Quattro. 482 miles on a tank. 14gal, IIRC.
 

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My Acura RDX 2015 uses CCM (Cylinder Control Management) and being a SUV even with moderate load gives me 33 MPG on a 250 miles highway trips I make on regular basis.
It has a 6 cylinder 3.5L engine but when on cruise it automatically shuts down 3 of the cylinder and runs only on the remaining 3 cylinders which drastically reduces the gas consumption. When on slight ramp it engages the 4th cylinder to provide some more power. When needed it turns on all 6 cylinders. All these switching happend in fraction of a second so it's not even noticeable. Not sure why VW hasn't copied this technology. Or may be they have!
 

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Discussion Starter #16
In the early 80's GM came up with a cylinder de-activation scheme called 8-6-4 I believe, to try and get more mileage from one of the V8s. Unreliable and quickly dropped.
 

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They have (via Audi) on the V8 engines in the US, but not the smaller engines. I know they have some on the 4cyl in EU, but not here. I am sure the people in the US would complain about it running rough on the 4cyl model.
 

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In the early 80's GM came up with a cylinder de-activation scheme called 8-6-4 I believe, to try and get more mileage from one of the V8s. Unreliable and quickly dropped.
GM has continued to develop that technology, and they use it on a number of models:

 

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It all makes sense to me that they use this technology in all their gas guzzler models. IF they don't and use it only in some of their models then may be using it is expensive or makes the engine more complicated.
 
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