Deville vs DTS horsepower and gas mielage

[kalderz]

Greetings!

This is my first post. I was unable to find an existing discussion that fit my question, so I will ask it in this new topic.

I own both a 2000 Deville and a 2004 DTS. The Deville gets 25/26 mpg highway 19/20 city gas mielage while the DTS gets about 22/23 highway and 16/17 city mpg.

The engines should be about the same, though the DTS is reported to be 300 horsepower vs. the Deville's 275 hp.

Can anyone help me by explaining what they did different to the DTS engine or drive system that might explain why the DTS has 300 hp vs 275 Deville and why the gas mileage differential between them would be so great (about 3 mpg average differential).

What makes this difficult for me to understand is that the Deville actual seems to have better acceleration than the DTS - even though it has less horsepower and gets better gas mileage by almost 15%.

In this regard the DTS disappoints. I thought that if someone could explain what GM did differently that perhaps I could mod my DTS so it performed as well as the Deville.

Or, if you know who or where I might inquire to get such an explanation.

Any help is appreciated. I love both cars, but would like to get better performance from the DTS.

Thanks!

[JasonA]

The DeVille's drivetrain (GM code LD8) has a 275 hp engine with 300 lb*ft of torque. It also has a 3.11:1 final drive.

The DTS's drivetrain (GM code L37) has a 300 hp engine with 295 lb*ft of torque. It also has a 3.71:1 final drive.

The difference in fuel mileage is often non-trivial as you are experiencing. This is mostly due to the differences in the final drive ratios. The DTS's engine is always turning faster at the same road speed compared with the DeVille.

The difference in power between the two engines is effected by the lift and duration of the intake camshafts. That's it. Otherwise, the two engines are identical.

The difference in seat-of-the-pants performance can probably best be described by using the torque curves of the two engines. Although there's only a peak torque difference of a measly 5 lb*ft, the LD8 engine (in your DeVille) makes much more torque over most of the operating range than the L37 engine does. And in fact, even though the L37 engine has 25 MORE peak horsepower, the LD8 engine actually makes MORE power through most of the RPM range than does the L37.

See this graph for an explanation. Up through about 5000 rpm, your DeVille is actually producing more power and more torque than does your DTS, even though the DTS is rated with "more" horsepower. People have often said before that the LD8 engines feel "punchier", or have more throttle response, than the L37 engines. Having said that, if you lined both of your DeVilles up at the dragstrip, I bet the DTS would win. Technically, it should be the faster car, because in a drag race, you are using the engine all the way to redline, where the L37 has the advantage. The L37 also has the shorter final drive, getting the engine into its powerband quicker. But the performance doesn't "feel" as strong, and the technical advantage it has is measured in the tenths of seconds, so we're not talking about Corvette vs. Cavalier here.

I prefer the LD8 engines (SLS, base Eldorado, DeVille) for these very reasons. Better fuel economy is just icing on the top. In 95% of the situations you drive in (or that *I* drive in anyway), the LD8 engine is best suited for the weight of the car. The master guru has said before that the LD8 engine (275 hp, actually 270 back then) was the initial design spec for the engine, since the power/torque curves are better suited to these large vehicles. Marketing had a lot to do with the 300 hp version (actually 295 back then). The 3.71:1 final drive was necessary with that engine due to its lack of low-end torque. If you put the L37 engine into an LD8 car, with the taller 3.11:1 final drive, it'd be a pig. It needs that short gearing to get up and go.

[Ranger]

In this regard the DTS disappoints. I thought that if someone could explain what GM did differently that perhaps I could mod my DTS so it performed as well as the Deville.

There is not much I can add to Jason's excellent explanation except that there is nothing you can do to change the DTS's characteristics. Like Jason, those are the reasons (along with suspension) that I went with the DHS as opposed to the DTS even though I much prefer the console and floor shift.

[KHE]

I have a SLS and a STS and the STS gets 3-4 MPG less than the SLS.

[thu]

It would be nice if GM would have put another gear on the STS or even a two-speed final drive. However, such is not so.

One thing about the STS that swayed me to buy it rather than the SLS were all the extra options.

[tjtjwdad]

Performance wise I've always felt the 275 HP versions were better, especially taking off. At freeway (65-70 MPH) speeds if you punch it the 300 HP versions feel like they have more pep. At the higher RPM's it seemed to me that the 275 versions started running out of steam while the 300 HP versions were still pulling hard.

The main reason I chose a STS over a SLS was the looks of the front end and the way they handled (which was far superior to the SLS IMHO).

Eitherway, both powerplants have plenty of juice.

[GreenMachine]

If you look at the long run of the STS its now better than ever with RWD and a 6 Speed automatic coupled to the northstar

Regarding the 275 running out of pep, your are right, the closer you get to redline the more it looses but the 300 Keeps going.

My deville has the 275HP and it will run right up to the 112mph Limiter in 3rd no problem, its after that magic number (and the end of second) that it will pull away as it wont have to shift until later and shifting higher up lets it drop right onto its peak torque curve.

Thats why its in the performance versions while as the 275 is the around town off the line car.

With the new VVT Northstar in the RWD applications you really can "have your cake and eat it too" so to speak.

[thu]

Another reason why I got the STS was the frickin' 112 MPH limiter. Dodge Neons will walk away from the SLS. I got tired of that.

Also, the MagneRide is a dream. It just rocks.

[JohnnyG]

Now taking this a step further, what do you all see as the major differences in performance and fuel mileage between the 2006 or 07 DTS I, II, or III VS. the DTS Performance. I'm not talking about handling, as we all know about Magnaride.....just engine and fuel economy. All versions, with VVT, pose a delema...do we indeed get to have our cake and eat it too?

By the way Jason Great Job! We may have found a new guru!

[GreenMachine]

Now taking this a step further, what do you all see as the major differences in performance and fuel mileage between the 2006 or 07 DTS I, II, or III VS. the DTS Performance. I'm not talking about handling, as we all know about Magnaride.....just engine and fuel economy. All versions, with VVT, pose a delema...do we indeed get to have our cake and eat it too?

By the way Jason Great Job! We may have found a new guru!

Well the new DTS DOES NOT have VVT, only the RWD northstars have it.

The STS RWD Northstar VVT propels it to 60mph in 5.8 seconds, thats much quicker than the old one. (under or over 7 if I remember). one of the options for the performance package is a limited slip differential, something our FWD monstors don't have so we get second gear starts when the traction control is off.

5 Speed Automatic

320HP@6400RPM

315HP@4400RPM (foot/lbs)

Final Drive Ratio of 3.23

[JohnnyG]

Well the new DTS DOES NOT have VVT, only the RWD northstars have it.

WOW! That's interesting, sorta makes the Lucerne look a lot better for $20,000 less doesn't it? The Lucerne can be had in version with Magnaride too I believe! And #2 behind a Japanese car to boot...how can you beat that?

[thu]

I was reading, some time ago, that one of things buyers of used BMWs should be aware of is the VANOS system. That's BMW's version of variable lift and duration valve timing. Repair on the VANOS system starts in the five-figure region.

How does the reliability of Cadillac's VVT rate?

I can't wait until direct injection comes to the N*!

[JimD]

Drove a V6 (VVT) 5 speed SRX for a week not long ago. I was impressed with the engine/transmission combination that never seemed to run out of torque. Bit of a gas hog, though.

Waiting for the dealer to loan me a demo STS with V8 (VVT) and 6 speed!!

[RichieR]

In this regard the DTS disappoints. I thought that if someone could explain what GM did differently that perhaps I could mod my DTS so it performed as well as the Deville.

There is not much I can add to Jason's excellent explanation except that there is nothing you can do to change the DTS's characteristics. Like Jason, those are the reasons (along with suspension) that I went with the DHS as opposed to the DTS even though I much prefer the console and floor shift.

I always found it unusual that the console/floor shift and analog dash was not available on the Base Deville/D'Elegance/DHS. The early to mid '90's Base Eldorados and Seville SLS had a digital dash with column shift as standard equipment, but there was a sports appearance package where you can get a floor shift with full console and analog instrumentation. I wonder why Cadillac didn't follow this same precendent with the Devilles. My father has a '97 Base Deville and he would have preferred the Analog instrumentation with the floor shift, but it's not even available on the Base Deville and the D'Elegance. Only the Deville Concours came with the analog dash and floor shift and it's standard. I guess Cadillac followed this same precedent with the 2000 + Deville models (the DTS is really the equivalent of the '97-'99 Concours and the DHS would be the equivalent of the D'elegance as far as standard equipment, ride, etc.)

Also, I like the leather seats on the Concours vs the Base Deville. The leather on the Concours is perforated and a much softer leather than the Base Deville. Again, these type of things should at least be optional on the Base Models.

[JasonA]

WOW! That's interesting, sorta makes the Lucerne look a lot better for $20,000 less doesn't it? The Lucerne can be had in version with Magnaride too I believe! And #2 behind a Japanese car to boot...how can you beat that?

I really like the Buick Lucerne. It has the 275 hp version of the Northstar, but I believe it comes with the 3.71:1 final drive (as the Bonneville GXP did). It runs 0-60 in 6.7 seconds, equalling the times of the 300 hp STS from the 1990s and early 2000s.

I sat in one the other day and it's just SO nice inside. I love the exterior styling; I like it better than the new DTS. I also love the classy portholes in the front fenders. That Buick is a steal of a car in my opinion, especially when had with the Northstar V-8.

[Bruce Nunnally]

http://www.buick.com/lucerne/specs_all.jsp

Apparently both the Lucerne CXL V8 and the CXS use the 3.11:1 final drive. The CXS gets better standard features, and a sport suspension.

[GreenMachine]

I actually don't like the floor shifter (for deville anyway). I find I have much more hip room and the ability "to have my baby next to me" with out. If its not a performance car I really don't need it (Seville, Eldorado, CTS, STS or STS-V, etc are all performance minded where as Deville is nothing but a cruiser with get up and go Its the tradiontal car). As Teeneager with one of the only cars left that seats 6....7 with 4 in the back...pretty good...well my buddies pickup was a differant story...anyway Its nice to have that extra room, especially on a trip its nice to have a cooler sitting on the floor with some drinks.

CLICK STICK SHIFTS AND SAFETY BELTS:

http://www.geocities.com/SunsetStrip/4925/...tickshifts.html

[Ranger]

I always found it unusual that the console/floor shift and analog dash was not available on the Base Deville/D'Elegance/DHS.

My DHS has the electroluminecent anolog dash. The only thing it is missing is the console & floor shift.

[JasonA]

Apparently both the Lucerne CXL V8 and the CXS use the 3.11:1 final drive. The CXS gets better standard features, and a sport suspension.

Bruce, thanks for the correction. I'm 99% positive the Bonne GXP used the 3.71 final drive with the LD8 engine. I thought the Buick did also. My mistake.

If its not a performance car I really don't need it (Seville, Eldorado, CTS, STS or STS-V, etc are all performance minded where as Deville is nothing but a cruiser with get up and go

Ignoring the floor shifter, that's what I really love about my SLS. It's not often these days where you can get a really great powertrain withOUT a "sporty" (stiff) ride. These Cadillacs are total class -- and they go fast to boot!

[JohnnyG]

Drove a V6 (VVT) 5 speed SRX for a week not long ago. I was impressed with the engine/transmission combination that never seemed to run out of torque. Bit of a gas hog, though.

Was that a 4 wheel drive version? I could have had an excellent deal on one of them, but the 20mpg highway rating scared me away.

An SRX with a N*, 2WD, VVT, 6speed, (RWD) should give highway fuel milage as good as my '99 STS (26.5 - 27) and hopefully better. Does anybody know if THAT is so?

[JimD]

Drove a V6 (VVT) 5 speed SRX for a week not long ago. I was impressed with the engine/transmission combination that never seemed to run out of torque. Bit of a gas hog, though.

Was that a 4 wheel drive version? I could have had an excellent deal on one of them, but the 20mpg highway rating scared me away.

An SRX with a N*, 2WD, VVT, 6speed, (RWD) should give highway fuel milage as good as my '99 STS (26.5 - 27) and hopefully better. Does anybody know if THAT is so?

The loaner I had was AWD. And 20 on the highway would be at 50 MPH with a tailwind.

[GreenMachine]

Drove a V6 (VVT) 5 speed SRX for a week not long ago. I was impressed with the engine/transmission combination that never seemed to run out of torque. Bit of a gas hog, though.

Was that a 4 wheel drive version? I could have had an excellent deal on one of them, but the 20mpg highway rating scared me away.

An SRX with a N*, 2WD, VVT, 6speed, (RWD) should give highway fuel milage as good as my '99 STS (26.5 - 27) and hopefully better. Does anybody know if THAT is so?

Maybe the STS or DTS but not so with the big SRX. I think its rated for 22 by the EPA with the V8 on the highway, Think it has to do with areodynamics or just simply shear weight maybe.....it may however be like our big old cadillac in that it appears to get better mileage cruising at 75-80mph simply because you have more "lift foot" situations when going down hills and up. Its a "performance utility" they say and we don't know if the EPA number is based on regular or premium fuel (althought the RWD northstar does indeed have a slight bump in compression over the 2000 FWD versions compression reduction).

The ultimate way to save on gas is to be on the road for less amount of time (usually).

[JohnnyG]

Thanks guys. I was hoping that a new Caddy would have SOMETHING going for it so I could justify buying one. As it is, I'm going to run the '99 'till the wheels fall off......81,111 and counting.

[JasonA]

Thanks guys. I was hoping that a new Caddy would have SOMETHING going for it so I could justify buying one. As it is, I'm going to run the '99 'till the wheels fall off......81,111 and counting.

You'll be qualified to make that statement in another hundred thousand miles or so. Until then, keep on enjoying the ride!

[GreenMachine]

Thanks guys. I was hoping that a new Caddy would have SOMETHING going for it so I could justify buying one. As it is, I'm going to run the '99 'till the wheels fall off......81,111 and counting.

Most do, but not the SUV's, they will always be gas guzzlers no matter what engine (non-hybrid) is in it. In that sense its a "fuel effecient" SUV if there was such a thing.

If your thinking of a new one look at the DTS or STS or for something smaller the CTS.

The STS is the performance "mid-size" sedan, sporting the RWD Northstar and a nice rating of 27 highway and 17 city so I'd imagine you'd get the 15 city and 25ish mpg that you currently get. It'll also get you to 60mph faster than the 99, in about 5.8-6.0 seconds.

The DTS is on the same platform as your 99 and remains in the front wheel drive configuration. Its also a very big car and on the road makes it presance known, that front grill remind me of the big o' caddy days.

check out www.cadillac.com and you'll be surprised at what the new ones offer.