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Found something interesting while looking through my old car magazines.
Road test data from Car & Driver, a 1970 Cadillac Eldorado and a 1973 Mercedes 450 SLC. I was surprised at the similar fuel mileage even though the Caddy weighed 1,000+ lbs more and had a much larger engine. Here are the actual stats:
I don't know what the Caddy's got ... but I worked on enough 4.5 liter M-B's of that era, drove them extensively, and owned several '72-'73-'74's to know that I got 15 mpg around town and about 18 mpg on the road cruising at 70-75 mph. And that was in Colorado using the cars along the front range and up into the mountains, which have a few passes of serious grades and altitude to cross.
Cars ranged from M-B 450SL's - 450SLC's - 450SEL's; the most fuel economical was a '72 M-B 350SL (one of the first 107's brought into the USA, these were all supposed to get re-badged as 450SL's because they came in with the 4.5 motor instead of the originally intended 3.5 motor; the car had manual crank windows and was essentially a "stripper" compared to later cars with cruise/climate/electric windows, and a host of weight gaining safety issues).
I'm sure that somebody could drive one of these cars aggressively enough to have such low fuel economy numbers, but I was well able to keep up with Porsches on day trips from Denver to Aspen ... at the most, they would be 5-10 minutes ahead of me on a typical cruise up to the mountains with reasonable driving, prudent passing of slower moving traffic, and so forth. We did this trip frequently enough for me to observe that I had essentially a relaxed luxury drive up to the mountains and return while the Porsche drivers had to work a lot harder to get ahead.
I'm not suggesting in any way that the M-B 450SL/SLC was the equal to the Porsche's in track performance ... we know that they weren't ... but that for an average mountain driver using average driving skills and prudent speeds (that's within the speed limits), the M-B would easily cover the same ground in real-world traffic/conditions mountain driving as the Porsche almost as quickly in 180-200 mile drives. More than once, my Porsche driving friends were at our agreed upon destination in Aspen, wringing out the sweat from their shirts ... and I drove up in the 'benz, perfectly relaxed, comfortable, and ready to go to lunch ....
I'd also mention that this wasn't a one or two time occurrence ... I had a fair number of clients based in Aspen who had me pick up/work on/deliver their cars from the Denver area to Aspen when they were headed to their homes there or upon the return. For many of them, it was a bother to drive their chosen cars up to the hills when they could have the car delivered to their home and fly from Denver to Aspen on the commuter airline. Or, for some, a car stored in Denver but available for them when they flew into Aspen from other points in the USA. I accomodated these customers for well over a decade .... and it wasn't just M-B's and Porsches that we delivered, we also did R-R, Saabs, Jags, Bentley's, and others ... in year-around conditions.
IMO, you'd be hard pressed to find a more stressed situation in the USA for a real world driving test for MPG on a car than driving at these altitudes and the climbs on the mountain passes here. There were a lot of cars of that era that could not maintain the speed limits on the roads due to a combination of power/gearing and handling characteristics ... while the M-B's were certainly capable of easily doing so in a very relaxed/refined manner. I could drive a 4.5 M-B on the trip without ever using the brakes, while many drivers of domestic vehicles were frequently using their brakes, even in the left lanes of the multi-lane roads and even on ascents with the curves ahead ....
Popular Science magazine also got similar fuel mileage with their test Mercedes. I would have to look up the exact year and model, but I remember that the figure was 12.8 mpg. The testers were surprised at the low mpg and even sent the car back to make sure it was tuned to factory specs. It was.
Here are some quick specs of a 1970 Chrysler 300-H which gave just under 13 mpg, even with its heavy weight, big engine and good acceleration...
Underpowered engines moving heavy vehicles often give worse gas mileage than a larger, more appropriate engine in the same vehicle, until you start throwing things like boost into it.
Kind of like the 4.3L V6 in GM trucks, vs 5.3L in the same truck...the 5.3 will beat it in every category (except for the "least amount of cylinders" category ) But overall it is really pretty hard to compare engines because of the technical differences involved.
The M-B 450SL's 107 chassis cars were a luxury personal touring car of a totally different concept and market niche than the big 'merican cars that you're bringing up here.
I know that I had a few rides in these big luxo-barges and that they didn't meet my needs or expectations for comfort, handling, or fuel economy in real world driving situations. I got to drive a series of Eldorado's that a friend bought because he liked the big heavy cars as tow cars for our sailboats ... all-up trailer rigs of a 700 lb boat and a 500 lb trailer, with camping/traveling gear in the very spacious trunks. Despite all the size/space, I rarely was comfortable in bench seats compared to the euro bucket seats with center console bolster.
OTOH, I've driven well over 150,000 miles in 450SL/SLC cars of that vintage and I know what I got for fuel economy, comfort, performance, and handling. These were very smooth capable cars for a two-seater luxury touring car. Fastest cars around? No. Absolute best sports car handling? No ... they were never intended to be so and were heavy enough that they weren't stellar performers, but they were most adequate when used as intended.
While I appreciate that you consider the road test reports from your sources to be impartial and accuate, I know what I got for many miles of driving these cars ... road test reports notwithstanding. I wasn't there to see their driving cycle, and if they were heavy footed accelerating on the 4.5 liter motor, the fuel economy could go into the low numbers. I don't drive that way, and with many years of driving M-B diesel cars ... since 1969 ... I'm not looking for leader of the pack stoplight to stoplight performance which the big 'merican luxo barges could deliver. The strength of the 107 M-B touring cars was their ability to quietly maintain a high rate of travel in comfort over roads that would have many other cars quite out of shape ....
This thread would make as much sense as if we were comparing full size Ford's or Chevy's of the era for their fuel economy to the top end luxo-barges you've cited. My 1964 Custom 500 Ford ... bought and used as a tow car for my sailboats ... delivered a steady 18 mpg with a 289 cu in V-8/3 speed auto ... note a fairly comparable displacement engine to the M-B V-8. So what? It was big, roomy, and adequate for it's intended purposes. Would it run with a 450SL down the road? of course not. But the 450SL was a less than desirable car for towing anything, although I have seen them with trailer hitches on them pre impact bumper days.
Underpowered engines moving heavy vehicles often give worse gas mileage than a larger, more appropriate engine in the same vehicle, until you start throwing things like boost into it.
Kind of like the 4.3L V6 in GM trucks, vs 5.3L in the same truck...the 5.3 will beat it in every category (except for the "least amount of cylinders" category ) But overall it is really pretty hard to compare engines because of the technical differences involved.
True. Also the low compression ratio didn't help fuel mileage, either.
I thought my point was very clear... that a big Eldorado got almost the same mpg as a smaller, much lighter Mercedes with a much smaller engine. To use another example, a '69 Dodge Coronet R/T with the 440 engine not only ran 0-60 mph 6.6 seconds and a 14.69 @ 97.4 mph 1/4 mile (on skinny '60s tires) but averaged 11.5 mpg. And a '67 Plymouth Fury III with a big-block 383 engine had a range of 10-14 mpg. So my point is that I would expect that Mercedes to get at least 14-15 mpg.
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The M-B 450SL's 107 chassis cars were a luxury personal touring car of a totally different concept and market niche than the big 'merican cars that you're bringing up here.
I know they were a different concept.... too bad their fuel mileage didn't match their compact size!
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I know that I had a few rides in these big luxo-barges and that they didn't meet my needs or expectations for comfort, handling, or fuel economy in real world driving situations. I got to drive a series of Eldorado's that a friend bought because he liked the big heavy cars as tow cars for our sailboats ... all-up trailer rigs of a 700 lb boat and a 500 lb trailer, with camping/traveling gear in the very spacious trunks. Despite all the size/space, I rarely was comfortable in bench seats compared to the euro bucket seats with center console bolster.
I currently own big, classic American luxury cars (not "barges") and they definitely exceed my expectations for comfort and meet them for handling. I would like better fuel economy, but then, they are no worse than some of the largest SUVs and trucks.
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While I appreciate that you consider the road test reports from your sources to be impartial and accuate, I know what I got for many miles of driving these cars ... road test reports notwithstanding. I wasn't there to see their driving cycle, and if they were heavy footed accelerating on the 4.5 liter motor, the fuel economy could go into the low numbers. I don't drive that way, and with many years of driving M-B diesel cars ... since 1969 ... I'm not looking for leader of the pack stoplight to stoplight performance which the big 'merican luxo barges could deliver. The strength of the 107 M-B touring cars was their ability to quietly maintain a high rate of travel in comfort over roads that would have many other cars quite out of shape ....
That's true... heavy-footed driving will certainly result in a drop in fuel economy. But my '66 Plymouth Fury VIP, with 383 engine, gives about 10.2 mpg when it includes some burning rubber, and getting rubber in 2nd gear and some full-throttle acceleration... the 10 mpg bracket is the same as some lighter cars with small V-8s (like that Mercedes).
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This thread would make as much sense as if we were comparing full size Ford's or Chevy's of the era for their fuel economy to the top end luxo-barges you've cited. My 1964 Custom 500 Ford ... bought and used as a tow car for my sailboats ... delivered a steady 18 mpg with a 289 cu in V-8/3 speed auto ... note a fairly comparable displacement engine to the M-B V-8. So what? It was big, roomy, and adequate for it's intended purposes. Would it run with a 450SL down the road? of course not. But the 450SL was a less than desirable car for towing anything, although I have seen them with trailer hitches on them pre impact bumper days.
I wasn't comparing with any luxo-barges; I was comparing with a luxury car (Cadillac Eldorado). You kind of made my point for me... a '64 Custom 500 Ford delivered 18 mpg with a small V-8 and 3-speed auto and a '73 Mercedes equipped very similar averaged quite a bit less. I just thought of something, though, maybe the emissions equipment on the Mercedes is the reason for the mpg figures it posted?
All depends what sort of driving you do. My 1.0 car did far more MPGs in city driving than my 2.4. My 2.4 does far more MPGs in distance driving than my 1.0 could.
As most US driving is long distance and even urban areas have lots of high speed routes it makes sense to have a larger engine or longer gearing.
(snip)
You kind of made my point for me... a '64 Custom 500 Ford delivered 18 mpg with a small V-8 and 3-speed auto and a '73 Mercedes equipped very similar averaged quite a bit less. I just thought of something, though, maybe the emissions equipment on the Mercedes is the reason for the mpg figures it posted?
Sorry, but my real world experience and that of a couple hundred customers of mine is that the 4.5 liter V-8 M-B got very comparable fuel economy to the 289 cu in powered Ford.
The emissions equipment of the 4.5 in 1972-1973 era was rather minimal; it was the changes in 1974 that were preliminary to the huge changes for 1975 which included catalytic converters ... poorly designed at the exhaust manifolds where they created too much underhood heat ....
However, this does raise a question: were the M-B cars tested CA versions or 49-state models? M-B did deliver two sets of emissions cars to the USA market at the time. The CA compliant cars were handicapped for power output as well as fuel economy compared to the 49 state cars.
We could, of course, get into other cars of the M-B line-up which delivered significantly better fuel economy .... 280SL's and 280SE's (both powered by a 2.8 liter 6 cylinder with mechanical FI) could deliver 21 mpg here at altitude, and the early 280SEL4.5's were at 18 mpg if driven reasonably. At that, I've had 1969/1970 300SEL6.3's deliver 20 mpg cruising at 75 mph and with a full load of people and luggage ... the 6.3 liter being much closer to the size of the big 'merican V-8's. To put the performance of the 109 chassis 6.3 liter car in perspective, 'benz did a promo with Jackky Iccx doing laps at the Beligum Spa Formula 1 race in (IIRC) 1969 ... where it set the pace for the race. 'benz had a poster that's somewhat famous of the car at speed in a turn there; the only reason 'benz couldn't run the race with the car was that nobody made tires at the time that would stay under such a large heavy car at speed for more than a lap or two. IMO, that's a measure of performance with a street legal/stock luxury upline car that a caddy wouldn't have been close to matching ....
A different tack on fuel economy would be to look at 126 chassis M-B's with a turbo diesel engine ... as much a luxury car as your caddy's, but able to deliver 28+ mpg in real world driving. While some might decry the lack of acceleration off the line, these cars were notable for being able to maintain freeway cruising speeds; there weren't too many domestic cars that could climb the approaches to the Eisenhower Tunnel in Colorado at speed while the turbodiesel simply hunkered down and kept on going ... not bad for 120 hp. I've passed a lot of cars in the Colorado mountains with my 123 chassis 300Dt's due to that deep torque curve ability of this motor ... and gotten 30 mpg with these cars on the diesel fuel of the era. Current low sulfur diesel doesn't seem to deliver the BTU/lb that we had years ago ....
As far as the concept of the cars go, comparing a 107 chassis M-B to a large
'merican luxury car doesn't make much sense to me. The smaller, lighter SL/C is not a high performance sports car, but a luxury touring car which delivers substantially better handling and performance than the luxury car you'd like to compare it to here. That capability in the 'benz comes at the expense of fuel economy; if you didn't need all the cruise/climate/electric windows in the 'benz to make it a luxury car, but made it more of a lightweight sports car ... the fuel economy numbers could be quite different. But the design parameters were what they were, and your attempt at comparing apples for oranges doesn't make sense .... the more valid comparison would be the 108 chassis 280SEL4.5, a sizable luxury 4-door car to the caddy's ... and the 108's readily achieved 18 mpg in real-world driving.
An interesting side trip to all this fuel economy thread is the 'benz 3.5 liter V-8 which found it's way into a limited number of cars in the USA. It was the prevailing V-8 engine in the euro 'benz market, and was a screamer ... an absolute performer that was most impressive for raw power and fuel economy in the late 1960's-early 1970's. Originally intended to be in the 450SL/C as the 350SL/C, the US emission compliant engine for 1972 was so badly derated that 'benz pulled it from the USA export production line and installed the larger 4.5 liter engine to restore some of the lost performance. You only have to get a ride in one of the 'benz 280SE/C (coupe or convertible 2-door model) with the 3.5 liter motor here in the USA to appreciate how quick and fast these cars were; even today, they are among the priciest of 'benz cars to buy and with good reason beyond just being rare and a superb example of the car building art. They are an amazing ride, even by the standards of more modern cars. Closest I ever got to owning one was a 1970 production 280SEConvertible which was an adequate performer ... but side by side with a customer's 1971 3.5 powered convertible, it was only adequate compared to something that really flew .... either way, both were far better at fuel economy than the large 'merican V-8 luxury cars of the era.
All depends what sort of driving you do. My 1.0 car did far more MPGs in city driving than my 2.4. My 2.4 does far more MPGs in distance driving than my 1.0 could.
As most US driving is long distance and even urban areas have lots of high speed routes it makes sense to have a larger engine or longer gearing.
Yes, it does depend on the sort of driving one does. But I would expect that Mercedes to do much better (fuel economy-wise) than that Cadillac.
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) But overall it is really pretty hard to compare engines because of the technical differences involved.
