Quote:
Originally Posted by marmac
they are getting --much-- better mileage today than years back.
I have bought 7 new cars in my lifetime starting in 1964. Not only am I getting much better fuel meleage, I get 250,000 miles + out of the newer ones with very little expense.
Years back, 125,000 miles was considered great.
I think many people who claim gas mileage hasn't improved are either quite young or have a short memory.
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Marmac, I beg to differ.
I once read an advertisement from around 1930, advertising the American Bantam "60". Its ad push was:
"Up to 60,000 miles per set of tires!
Up to 60 miles per gallon of gasoline!
Up to 60 miles per hour!"
Okay, so we'd rather have cars that go faster than 60 these days. However, if the engine in that little car had been a bit bigger, it'd probably have been able to hit 85 and still get 50 mpg.
My first car was a 1972 Cadillac Sedan DeVille. Empty, it weighed almost 4,800 pounds. It would average 13-14 mpg on the highway, and I once squeezed it up to 15 by keeping it at a more fuel-efficient speed of 55 mph.
That engine was so powerful that pushing the gas pedal down much beyond the halfway point risked a tire burnout from a standing start. It produced 385 foot-pounds of torque (220 horsepower). Note that the horsepower number is low compared to the torque number because it was engineered to be a low-revving engine (4500 rpm redline, would spin 2200 rpm @ 65 mph). It also had a "slushbox" 3-speed automatic transmission.
It had NO computerized gizmos beyond the normal electrical circuits for operating the idiot lights on the dashboard. It was not fuel-injected, instead boasting the usual 4-barrel Rochester Quadrajet carb outfitted to most of those engines.
The modern equivalent is the 2008 Cadillac DTS. Information gleaned from the Cadillac website shows that the more powerful engine available with this car puts out a maximum of 295 foot-pounds of torque, and the powertrain provides 22-23 mpg on the highway. (That's the EPA estimate, which is usually too high. Drivers of these cars will probably be lucky to get 20 mpg on the highway, driving their cars the way I used to drive my Caddy to get 13.5 highway mpg.) Bear in mind that the transmissions in these cars are 4-speed automatics with lockup torque converters. Had my Caddy had one of those, surely it would've gotten better gas mileage.
The new Caddy is also about 750 pounds lighter than mine ever was, at a curb weight of 4,009 pounds.
Anyway, I'm oversimplifying the mathematics here... but the newer Cadillac's engine only puts out 76.6% of the power that my Cadillac's engine put out. Although there are some other factors which would go into this equation, let's keep things simple. I'm a physics major, so I know certain things about the physics of car engines. In an ideal environment, halving a car's engine would halve its power output but also double its fuel efficiency.
So, an engine putting out .766 of the power of my Cadillac's engine should produce (1/.766)*13.5 = 17.62 highway mpg.
The newer Cadillac weighs 84% of what my Cadillac weighed. Again, in an ideal environment, halving the weight of a car should double its fuel efficiency because the engine only has half of the weight to pull. Taking the 17.62 highway mpg that I got in the last calculation, and dividing it by .84, yields 20.98 mpg.
If you weren't following the math, I just determined that, in ideal circumstances, my old 1972 Cadillac, had its engine been shrunk so that it produced only the power of the 2008 Cadillac's engine (but otherwise had the same properties), and had it weighed the same amount as the 2008 Cadillac, would've gotten approximately 21 highway mpg even with its slushbox 3-speed non-overdrive automatic transmission.
Even if my assumptions are off, they can't be that far off.
I am now going to run the calculations again, using more real-world numbers I gleaned from the Dodge website. The Charger, with 2.7L V6 engine that puts out 191 ft-lb of torque, gets 21 average mpg and weighs 3727 pounds. The SRT8 version, with 6.1L V8 that puts out 420 ft-lb of torque and weighs 4160 pounds, gets 15 average mpg.
The lighter car weighs .896 of the weight of the heavier car. The lighter car has .455 of the power of the heavier car. Combining those factors yields .407, meaning, in the theory of my calculations, the lighter car should have an average fuel economy reading of 36.86. Obviously, that didn't happen. A power & weight reduction factor of .407 yielded a fuel economy increase factor of 1.4. I will redo the calculations now, assuming linear extrapolation.
The power and weight reduction factor of the 2008 Cadillac is .643. Extrapolating a fuel economy increase factor from the Dodge figures yields a theoretical fuel economy increase of 1.24. That'd mean that my 1972 Cadillac, had it had a 4-speed overdrive transmission with lockup torque converter, a less powerful engine with all other properties the same as the original, and 768 pounds less weight, should've returned highway fuel economy of 16.74.
The new Cadillac would probably get about 20 mpg in highway driving, based upon my knowledge of how real-world figures differ from EPA estimates. Theoretically, my car (which was 36 years older) would've gotten 16.74 - 21 highway mpg with two simple alterations. Who knows what its original highway fuel economy would've been if they had made 4-speed lockup automatic transmissions in 1972?
Now, enough theory. Let's talk about real-world examples.
I have a 1982 Dodge Ram pickup (standard cab, long bed) with a 6-cylinder engine and a stick shift. It will get 16-18 mpg on the highway, depending on my speed. The 2008 Dodge Ram pickup with 6-cylinder engine and stick shift is EPA-estimated at 19 mpg highway. That means it'd probably get no more than 18. Is this really progress, in 26 years?
I had a 1987 Dodge Ram B250 conversion van with 5.2L carbureted V8 engine and 3-speed slushbox automatic transmission. It would AVERAGE 14.5 mpg and was known to be able to hit 17.5 on the highway. Dodge no longer makes the Ram conversion van, so I compared it to the current Chevrolet 3/4-ton Express 2500 conversion van. With the 5.3L fuel-injected V8 engine, it's rated at 12 mpg city and 16 highway. Seems like my oldie did even better than the new one!
I had a 1981 Cadillac Coupe DeVille. It's about the same weight as the current 2008 Cadillac DTS. With its 6.0L V8 engine with the first-ever "Active Fuel Management" system, I squeezed it up to 17 mpg average, and it'd get about 21 on the highway. The 2008 DTS probably doesn't do better than that if its EPA estimate is 22-23 mpg highway. Again I ask... in 27 years, is this really progress?
I had a 1985 Chrysler New Yorker with the turbocharged 2.2L four-cylinder engine and three-speed slushbox automatic. At 2,583 pounds and 146 horsepower, it's comparable to today's Dodge Caliber. The Caliber is the lightest and smallest vehicle currently in the Chrysler Corporation lineup. My in-laws own one, with the CVT automatic transmission. At roughly 3,000 pounds with a 2.4L four-cylinder engine, my mother-in-law says that it averages about 26 mpg. My 1985 New Yorker averaged... you guessed it... 26 mpg. I don't call that progress, for 23 years of automotive technology improvement.
So.... really.... do modern cars get better gas mileage? I, for one, say "not really". Even if they have managed to eke out a 1-mpg or 2-mpg gain on cars from 30 years ago, that comes at huge cost. Newer cars have all kinds of computerized crap-ola which will only fail at some point in the future, requiring huge repair bills because Tony the gas-station mechanic won't touch the thing and you have no choice but to get it repaired at a dealership where they'll hit you for $100.00/hour in labor.
I'd prefer to buy a car from 30 years ago, for a tiny fraction of what a new car would cost, and enjoy 1 or 2 mpg less than what a new car will get. At least, when something breaks, I can take it to Tony and he'll fix me up in no time for $35/hour.
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