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Other factors: In the late 1970's and 1980's cars were designed with a 55 mph-65 mph speed limit in mind. Their engines had enough power for that range and often not a lot more. EPA fuel economy ratings were based on those speeds. Today's cars have to have sufficient power to run at 75 mph sustained speeds--which means that they often have to sacrifice some fuel efficiency at slower speeds. Americans have also gone silly over expecting even mundane economy cars to go 0-60 in 8 seconds or less, and that requires a lot of engine power. For what they are designed to do, today's engines are more powerful, usually considerably more fuel-efficient, run cleaner, and last longer than any engine made 30 or 40 years ago, but higher road speeds, along with more horsepower and torque eat into fuel economy. If we were back in a place with 55-65 mph speed limits, and people would accept vehicle performance and acceleration rates that were common in, say, 1985, cars would typically be getting 40-50 mpg or more with today's engine technology.
I don't understand this, it seems scientifically impossible.
For 10 years 2002-2012, I drove a 1992 Cadillac Fleetwood Brougham. IIRC the door sticker said it had a 5350LB curb weight, a 5.0L V8 engine seated 6 with miles of extra room, full body on frame. EPA estimated 17/23, my actual experience was 15/25. I am in California and was frequently vilified for driving such an environmentally unfriendly vehicle. I have not had any car for2 years, and now I am shopping. Obviously cars are smaller, have smaller engines, weigh less, etc. However, and this is what is perplexing me: They, according to the EPA all have noticeably worse gas millage than my land yacht caddy.
Todays test drive was a 2002 Lexus 400, smaller car, obviously. Only had a 4.0L engine, but was EPA rated at 16/23. Now how does it happen, with CAFE standards and the price of fuel, that you can take a car, eliminate 1/3 of the weight, ditch the frame, remove room for1 passenger, drop the displacement by 20%, and kill the tow capacity and end up with WORSE fuel economy. Kinda seems to violate the laws of physics.
Seriously, I am dying to learn something here.
My Father 83' Coupe DeVille with the HT4100 got 17/23 on a regular basis. We hot 25 mpg on a trip down to Atlantic city when it was about 5 years old and had 60,000 miles on it.
I assume you're talking about the LS430.. That is rated at 16/23 and requires premium gas.. Your old Caddy was actually rated at 15/23 and regular gas. Both those are on 'current' standards
When the Lexus LS430 was new, its rating was 18/25. As a previous poster mentioned, the EPA changed fuel economy ratings in 2008.
You're also off on the weight a bit on the old Caddy.. It was 4277 lbs. Weight of the LS430 is 3955lbs (Curb weight)
You do, however, have a valid point. You would think that there'd have been more mileage improvement.. But.. Noone cared about gas between 1992 and 2002, really.. It was 2005 that the concern came in, and about 2008 before it started getting reflected in vehicles.
But.. Even the brand new 2014 Lexus LS460 only gets 16/24. About the same as a 1992 Ford LTD, which was another 'boat' car. That is actually more surprising to me.. Generally what you've seen in the recent models is a huge disparity between city and highway mileage. Take the Chevy Cruze as an example.. 26 city, 38 highway.. That's due to these newer 6,7 and 8 speed transmissions.
I just looked up every car I owned the past 15 years and the new adjusted mileage was accurate for what I experianced on a regular basis except for one car.
EPA required pollution standards are ruined auto performance. 35 years ago, I was driving cars that were 4 door midsized sedans and easily got 30 mpg on the highway. But with the pollution equipment ruining the performance of the engine, you aren't going to get the needed power or mpg.
Not entirely. Vehicle curb weights increased due to mandated safety standards, airbags, etc. That is a big reason why compact cars got such high MPG in the 1980s.
As long as we're making comparisons between cars that didn't exist, my 1984 Prius got over 100 MPG while the 'new' ones only get half that. Can someone explain this???
Ultimately it's about energy. Acceleration requires the same energy regardless of the number of cubes in the engine. Air drag requires the same energy as well. That's why my wife's 4cylinder gets only slightly better mileage than by 5.3 V8. There's only so much you can do about size because people aren't getting smaller. Then try to package that in a energy efficient body.
On top of that, it seems almost every gain in engine efficiency is offset by some new environmental gadget that lowers it.
Ultimately it's about energy. Acceleration requires the same energy regardless of the number of cubes in the engine. Air drag requires the same energy as well. That's why my wife's 4cylinder gets only slightly better mileage than by 5.3 V8.
This is absolutely true, but we have to remember that at "normal" operating conditions - puttering around town - so little horsepower is required to overcome aerodynamic drag or rolling-resistance, or to accelerate the car at "normal" rates, that a substantial portion of the overall power budget goes to motoring losses in the engine, to waste heat in the cooling system and so forth.
To give a rough example, the average car drag coefficient is something like 0.35, and the equivalent frontal area is around 25 square feet. At 55 mph, that works out to around 10 hp required to overcome aerodynamic drag. Assuming a coefficient of rolling friction of 0.015 and a 4000 lb car, that's also around 10 hp to overcome rolling resistance.
It takes around 25 ft-lb of torque to hand-crank a V8, disregarding compression-losses. If that V8 is spinning at 3000 rpm going down the highway at 55 mph, that's around 15 hp dissipated by internal resistance in the engine - and that is completely disregarding pumping-losses or driveline losses.
The point is that at moderate speeds, in the above example, about half of the total expended power is to just keep the rotating-bits (crankshaft, driveshaft, etc.) in the car rotating. The other half is power to actually move the car down the road. If we take the exact same car body, and equip it with a puny engine, vs. a huge monster engine, the power required to move the body down the road will be essentially the same, but the motoring-losses in the larger-engine case will be larger.
If instead of 55 mph we go at 150 mph, motoring-losses become moot. Then it's all about aerodynamics.
compare the performance and Horsepower.
the lexus has 150HP more than that caddy
more horses drink more fuel
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