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Discussion Starter · #1 · (Edited)
:brick: Frankly I'm tired of all the talk of FWD being the layout of choice based on the MYTH that fuel economy will be better than if that vehicle had its power routed to the rear wheels

http://www.gminsidenews.com/forums/f19/fuel-economy-myths-debunked-long-66762/

Not too long ago I wrote up a thread entitled "Fuel Economy Myths Debunked!" and using fueleconomy.org, part of my researched included showing that FWD is not all that it's cracked up to be when fuel economy and CAFE is a concern. Discussion of the next Impala being on a "super" Epsilon II platform instead of Zeta, as planned before, brought it back to mind.

The arguments that I've seen come up about loss of efficiency are additional rotating mass, torque having to make a right angle in the rear differential, and additional components and thus weight. REGARDLESS, my examples PROVE that these theories still do not result in a loss of fuel economy.

Even if there is a difference...would you be willing to give up one mile per gallon when it comes to picking between FWD and RWD?

Below is the research I conducted for my previous thread:

FWD is more efficient than RWD

2008 CTS: 3.6L DI, 6 speed auto: 17/26, 20 MPG combined
2008 Malibu: 3.6L, 6 speed auto: 17/26, 20 MPG combined

An engine of similar displacement and output (direct injection is mixed in though, keep that in mind) in vehicles of somewhat the same size and weight (I haven't looked it up though) with modern automatic transmissions get THE SAME mileage! Lutz gets a FAIL for pulling this one and blaming CAFE on his troubles.

and for you Chrysler fans, and to further show this:

2004 Intrepid: 3.5L, 4 speed auto: 16/25, 19 MPG combined
(neither vehicle is listed for 2005?)
2006 Charger: 3.5L, 5 speed auto: 17/24, 20 MPG combined

The Charger's 3.5L has a little more power than the Intrepid's and has a 5 speed auto versus the 4, for the record, but still, city MPG is actually better and the difference on the freeway is negligible. I recognize that the Charger's engine is a little more enhanced/tuned.

I have thought up a few more fair examples, the first being a pair of Ford products from recent history:


2000 Continental: FWD, 4.6L, 4 spd AT...15/23 freeway, 18 MPG combined
2000 Town Car: RWD, 4.6L, 4 spd AT...16/23, 18 MPG combined


Both vehicles are large, luxury sedans with the Modular 4.6L. Heck the Town Car has a frame to lug around :rolleyes:


How about a look at a pair of in-production Cadillacs?


2008 DTS: FWD, 4.6L, 4 spd AT...15/23, 18 MPG combined
2008 STS: RWD, 4.6L, 6 spd AT...15/24, 18 MPG combined


Again, both are large luxury sedans, both utilize Northstar V8s...but the STS actually gets better mileage? Tell me Lutz, how could this possibly be!? You've shelved RWD vehicle plans BECAUSE of mileage!? :mad:


Coupes from recent history, both 3800s...

2002 Firebird: RWD, 3.8L, 4 spd AT: 17/28, 21 MPG combined
2002 Grand Prix: FWD, 3.8L, 4 spd AT: 17/27, 20 mpg combined


Getting a little farther back in history than I want to, but...

1992 Fleetwood: RWD, SBC, 4 spd AT: 15/23, 17 MPG combined
1992 Deville: FWD, 4.9L, 4 spd AT: 15/23, 17 MPG combined

Keep in mind in '92 the Deville was still the small-style and is a little smaller inside and out than the B-body Fleetwood, and that's got a frame to move. The 4.9L had port fuel injection while the Fleetwood still had TBI

I don't want to be redundant but I can keep going...

2007 Lacrosse CXS: FWD, 3.6L, 4 spd auto: 17/25, 20 MPG combined
2008 CTS: 3.6L DI, 6 speed auto: 17/26, 20 MPG combined
2008 Malibu: 3.6L, 6 speed auto: 17/26, 20 MPG combined

Too old, but if it helps, a '90 3.1L AT Camaro gets one less MPG over a '90 3.1L AT Lumina coupe...which car would you chose?

If I knew my Bimmers I'd add them in as well. Do you guys think I have a valid argument?
 

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This is all the proof I need.

Cold Calculating Car Power must be RWD! :)

I will contact The Makers tomorrow morning and order them to change everything to RWD.

Now, I hope you're happy. Go to bed.
 

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My RWD 1993 Lexus GS300: Averages 21mpg(real number, not estimated)
My FWD 2003 Toyota Matrix: Averages 33mpg(real number, not estimated)

In my personal experience as displayed above FWD gets much better mpg.

What's that? Not apples to apples you say? Well, so what, FWD is cheaper and less complex, and it ain't going anywhere, get over it.
 

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My RWD 1993 Lexus GS300: Averages 21mpg(real number, not estimated)
My FWD 2003 Toyota Matrix: Averages 33mpg(real number, not estimated)

In my personal experience as displayed above FWD gets much better mpg.

What's that? Not apples to apples you say? Well, so what, FWD is cheaper and less complex, and it ain't going anywhere, get over it.
Are you insane? You're comparing a car that's ten years older, and has a 3.0L V6 engine to one that has a 1.8L 4-banger.

Anyway, I think FWD gets its "better mileage" because of less drivetrain power loss due to the lack of a driveshaft (and the weight that comes with it). Gearing also plays a big part.
 

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Are you insane? You're comparing a car that's ten years older, and has a 3.0L V6 engine to one that has a 1.8L 4-banger.

Anyway, I think FWD gets its "better mileage" because of less drivetrain power loss due to the lack of a driveshaft (and the weight that comes with it). Gearing also plays a big part.
It has an I6 engine.
vsd said:
What's that? Not apples to apples you say? Well, so what, FWD is cheaper and less complex, and it ain't going anywhere, get over it.
 

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It has an I6 engine.
I prefer my Suburban 4WD over an 18 wheeler cause it gets better mileage.

"What's that? Not apples to apples you say? Well, so what, 4WD is cheaper and less complex, and it ain't going anywhere, get over it."
 

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No, your blanket statement is wrong. FWD and RWD are only equal in fuel economy if you make a bunch of unrealistic assumptions.

First of all, FWD is more space-efficient than RWD, which means you get more interior room for the same exterior. This is where you are 'cheating' in your comparisons. The CTS and Malibu are about the same size externally, but the Malibu has more usable interior room. A RWD car equal to the Malibu would be larger and therefore heavier and therefore less fuel efficient. We saw this with the 1980s H Cars (Olds 88 etc) which were actually larger inside than the RWD B-bodies they replaced. (Also comparing MPGs of a sport luxury model with family sedan is bogus.)

The other thing you are completely ignoring is marketing. A RWD car will be positioned as a performance car and therefore will have to support much more powerful engines. Zeta can support ~500HP while Epsilon I can only support ~250HP. Bigger frame, bigger suspension = heavier and less efficient. Don't even pretend that you could sell a large RWD Chevy without the smallblock to go with it!

Furthermore the attach rate of V8s is much higher for RWD cars (compare Charger versus Impala for example), and that has a effect on CAFE averages.

So, yes can have a RWD car that's almost as efficient as FWD car, but only if it is smaller inside and is limited to small engines.
 

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Discussion Starter · #9 ·
No, your blanket statement is wrong. FWD and RWD are only equal in fuel economy if you make a bunch of unrealistic assumptions.

First of all, FWD is more space-efficient than RWD, which means you get more interior room for the same exterior. This is where you are 'cheating' in your comparisons. The CTS and Malibu are about the same size externally, but the Malibu has more usable interior room. A RWD car equal to the Malibu would be larger and therefore heavier and therefore less fuel efficient. We saw this with the 1980s H Cars (Olds 88 etc) which were actually larger inside than the RWD B-bodies they replaced. (Also comparing MPGs of a sport luxury model with family sedan is bogus.)

The other thing you are completely ignoring is marketing. A RWD car will be positioned as a performance car and therefore will have to support much more powerful engines. Zeta can support ~500HP while Epsilon I can only support ~250HP. Bigger frame, bigger suspension = heavier and less efficient. Don't even pretend that you could sell a large RWD Chevy without the smallblock to go with it!

Furthermore the attach rate of V8s is much higher for RWD cars (compare Charger versus Impala for example), and that has a effect on CAFE averages.

So, yes can have a RWD car that's almost as efficient as FWD car, but only if it is smaller inside and is limited to small engines.
Respectfully:

Malibu interior dimensions (Motor Trend):

front headroom (inches): 39.4, rear headroom (inches): 37.2, front hip room (inches): 53.0, rear hip room (inches): 52.1, front leg room (inches): 42.2, rear leg room (inches): 37.6, front shoulder room (inches): 55.9, rear shoulder room (inches): 53.9 and interior volume (cu ft): 95.0


CTS dimensions:

front headroom (inches): 38.8, rear headroom (inches): 37.2, front hip room (inches): 55.1, rear hip room (inches): 54.1, front leg room (inches): 42.4, rear leg room (inches): 35.9, front shoulder room (inches): 56.7, rear shoulder room (inches): 54.7 and interior volume (cu ft): 98.0


Conclusion: they're close enough.


I agree that a RWD vehicle will be marketed more for performance and need stronger, heavier components to support the power in addition to a larger engine, HOWEVER...

As you mentioned, Epsilon 1 is only good for the 250-some HP we're at. Sigma, however, is good for at least 550 HP. The G8 is on Zeta, and good for at least 500 HP (HSV W427), but with the 3.6L that still gets similar mileage as the Epsilon.

The Charger's LX platform is good for 425 HP, but with a 3.5L, is comparable to the Intrepid.

If it came down to it (CAFE) and GM didn't want to offer V8s in their Zeta cars (like the next Impala, if it gets to be on Zeta), so be it. Chrysler sells plenty of 2.7L and 3.5L Chargers and 300s.
 

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No, your blanket statement is wrong. FWD and RWD are only equal in fuel economy if you make a bunch of unrealistic assumptions.

First of all, FWD is more space-efficient than RWD, which means you get more interior room for the same exterior. This is where you are 'cheating' in your comparisons. The CTS and Malibu are about the same size externally, but the Malibu has more usable interior room. A RWD car equal to the Malibu would be larger and therefore heavier and therefore less fuel efficient. We saw this with the 1980s H Cars (Olds 88 etc) which were actually larger inside than the RWD B-bodies they replaced. (Also comparing MPGs of a sport luxury model with family sedan is bogus.)

The other thing you are completely ignoring is marketing. A RWD car will be positioned as a performance car and therefore will have to support much more powerful engines. Zeta can support ~500HP while Epsilon I can only support ~250HP. Bigger frame, bigger suspension = heavier and less efficient. Don't even pretend that you could sell a large RWD Chevy without the smallblock to go with it!

Furthermore the attach rate of V8s is much higher for RWD cars (compare Charger versus Impala for example), and that has a effect on CAFE averages.

So, yes can have a RWD car that's almost as efficient as FWD car, but only if it is smaller inside and is limited to small engines.
What he said.

It does raise the question on why GM's FWD platforms are getting so heavy, though. If you are going to use FWD, it seems to make sense to maximize the advantage of the platform (that you can get more interior room out of a smaller, lighter car). GM's FWD mid-sizes are still lighter that comparable RWD cars, but not by as much as they used to be.

If the next FWD Impala had the same interior volume and trunk as the G8 ... and weighed in a 3500 lbs in full option, v6 trim, I think you'd end up with a car that offered better fuel economy and equivelent room -- just what a lot of buyers want right now.
 

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No, your blanket statement is wrong. FWD and RWD are only equal in fuel economy if you make a bunch of unrealistic assumptions.

First of all, FWD is more space-efficient than RWD, which means you get more interior room for the same exterior. This is where you are 'cheating' in your comparisons. The CTS and Malibu are about the same size externally, but the Malibu has more usable interior room. A RWD car equal to the Malibu would be larger and therefore heavier and therefore less fuel efficient. We saw this with the 1980s H Cars (Olds 88 etc) which were actually larger inside than the RWD B-bodies they replaced. (Also comparing MPGs of a sport luxury model with family sedan is bogus.)

The other thing you are completely ignoring is marketing. A RWD car will be positioned as a performance car and therefore will have to support much more powerful engines. Zeta can support ~500HP while Epsilon I can only support ~250HP. Bigger frame, bigger suspension = heavier and less efficient. Don't even pretend that you could sell a large RWD Chevy without the smallblock to go with it!

Furthermore the attach rate of V8s is much higher for RWD cars (compare Charger versus Impala for example), and that has a effect on CAFE averages.

So, yes can have a RWD car that's almost as efficient as FWD car, but only if it is smaller inside and is limited to small engines.
Thank you.

FWD is more efficient than RWD. Period.
 

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FWD is a far better alternative than RWD.

FWD has cheaper R&D, lighter platform, more interior room. Yes the loss to the rear tires is not as noticeable as it used to be, but there isn't much reason for RWD, especially these days unless you want performance.
 

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F14Crazy, you cherry picked your examples to make your point.

Consider that the Hyundai Azera, Ford Taurus, and Toyota Avalon all have significantly more space than the Malibu or CTS, more power, and better fuel economy. In fact, they have similar or more space than the Pontiac G8 and Chrysler 300 V6 and better fuel economy than those models too.

There are some inefficient FWD sedans available, but they're most inefficient because they're old. Newer models do very well for fuel economy - generally 5-15% better than RWD competitors. That adds up, both in CAFE standings and also in sales to people who are fearful over the price of oil. ( Oil is cheaper now... but will it stay cheap? Who knows? )
 

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The difference in fuel economy between a rear wheel drive and front wheel drive is especially noticeable when comparing real world numbers in winter driving conditions. Front wheel drive vehicles have an advantage when it comes to "take-off" situations in snowy and icy conditions. Front wheel drive will pull the vehicle from a stop more efficiently than a rear wheel drive. The quicker take off and reduced wheel spin due to a loss of traction results in much better fuel economy.
 

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If you had posted this anywhere other than where automotive enthusiasts hang out, you might have gotten away with your claim. But you’re not quite accurate enough for here.

While being FWD or RWD is not typically enough to make one vehicle more fuel efficient than another, there are other extenuating circumstances that you’ve conveniently overlooked.

The most important of these is weight. FWD vehicles typically package the transmission and axle into the same housing, saving weight and eliminating the need for a driveshaft, which further reduces the weight. Then there’s the more complex rear suspension on a RWD vehicle, again adding weight. For the same vehicles, the FWD vehicle would be lighter and, therefore, more fuel efficient. Or on the other hand, allowing the designers to engineer in MORE weight into the FWD vehicle to make it more solid or quieter or larger inside.

And all of this overlooks the traction and packaging and cost reasons, which obviously favor the FWD setup.

Now let’s get to your examples:

2000 Continental: FWD, 4.6L, 4 spd AT...15/23 freeway, 18 MPG combined
2000 Town Car: RWD, 4.6L, 4 spd AT...16/23, 18 MPG combined
More powerful DOHC engine in the Continental compared to the SOHC engine in the Town Car.

2008 DTS: FWD, 4.6L, 4 spd AT...15/23, 18 MPG combined
2008 STS: RWD, 4.6L, 6 spd AT...15/24, 18 MPG combined
More efficient 6-speed transmission in the RWD vehicle.
2002 Firebird: RWD, 3.8L, 4 spd AT: 17/28, 21 MPG combined
2002 Grand Prix: FWD, 3.8L, 4 spd AT: 17/27, 20 mpg combined
Quieter Grand Prix allowing for five passengers compared to the sportier (read: louder) and less roomy Firebird.
1992 Fleetwood: RWD, SBC, 4 spd AT: 15/23, 17 MPG combined
1992 Deville: FWD, 4.9L, 4 spd AT: 15/23, 17 MPG combined
Are we talking the 170hp L03 or the 175hp L05 vs the 200hp 4.9L?
2007 Lacrosse CXS: FWD, 3.6L, 4 spd auto: 17/25, 20 MPG combined
2008 CTS: 3.6L DI, 6 speed auto: 17/26, 20 MPG combined
2008 Malibu: 3.6L, 6 speed auto: 17/26, 20 MPG combined
Too old, but if it helps, a '90 3.1L AT Camaro gets one less MPG over a '90 3.1L AT Lumina coupe...which car would you chose?
Yes, too old. The newer cars are CLEANER than the 3.1L.

And my argument doesn’t take into account that all manufacturers design to a standard. Cars are engineered for a target fuel economy…not for peak fuel economy. Isn’t it odd that so many of GM’s products now get 17mpg (on the new test standard) or that they got 18mpg (on the old standard) in years past? No matter what engine or packaging?

Your argument is assuming apples-to-apples when you’re not taking into consideration all of the other influences. If you were designing a car that was inherently lighter (FWD), wouldn’t you design in MORE weight to get the vehicle to be quieter or smoother or more powerful or roomier? All of these qualities mean more to the average buyer than FWD or RWD.
 

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Here's my two cents......

If GM and/or the other domestics actually designed/built/marketed a RWD 4-door in the same way they did their FWD bread-and-butter 4-doors, then I bet you would see this all turn moot quite quickly. We've seen that the Big 3 can get the job done when they actually give 100% or more......

However, the Asians have perpetuated the 'myth' that FWDers are just as good, if not markedly better all-around than their RWD counterparts. The fact that FWD midsizers & compacts are two of the leading market segments today underscores this myth and also gives the lazy, ignorant & inept minds in Detroit the perfect excuse to spend their money & resources elsewhere......instead of trying to reinvent the RWD family sedan.

The case of Chrysler/Dodge is pretty much a bright flash in the pan. They had their fun with all that cab forward BS in the mid-late 90's, then came out with two, big, brash & unapologetic American RWD sedans. However, the fact that they lag behind GM & Ford in many areas--both under the hood and in the cabin--blunted whatever impact they may have had on the marketplace beyond all the 'Car of the Year' hoopla a few yrs. back. Now they're trying to play catch up and as you can very well see, it's too little, too late for the players in Auburn Hills.
 

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Too old, but if it helps, a '90 3.1L AT Camaro gets one less MPG over a '90 3.1L AT Lumina coupe...which car would you chose?
I would put my money in a bank, buy a bus pass then buy a '94 Formula 6-speeder or a '90 Corvette maybe

Basically apples and apples the FWD is a better layout. Better utilisation of space, lighter, less moving junk. There is a lot of energy to spin a propeller shaft, it is like unsprung weight ;)

That said comparing two cars of similar dimension your difference is little...



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Are we talking the 170hp L03 or the 175hp L05 vs the 200hp 4.9L?
a 93 Fleetwood RWD would have the L05 (350 TBI SBC) standard...as did Buick in the Roadmaster...


That being said...if I drive just 55MPH on my 1993 Roadmaster sedan...I can get 22-23MPG....add 70-75 interstate...it drops to 20-21...
BTW, it's a 2.56 final drive ratio...


My 98 FWD Park Avenue can achieve 31-32 going 55mph straight away, add higher speeds on I system, it drops to about 29-30MPG...it's a 3800 with a 4t-65e & the 3.33 final drive ratio...

Old Dood, my good friend had once challenged those claims given his Park Avenue...I had taken several pictures of the DIC readings on my park ave to show my claim....however for some reason I can't upload pictures from either my personal computer nor my office computer onto GMI...:confused:
 
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