We don't need hybrids,.. we need 55MPH! - a long winded ramble.

[rcpratt]

Worst idea ever.

 

[spidey07]

Drag due to wind resistance goes up by the square of the velocity. that does not matter when you are going 20-30 mph, because most vehicles are aerodynamic enough that other things (like wheel friction, engine drag, etc) factor in a bit more.

But when you start getting up to 50-60 mph, it jumps up in effect quite dramatically. A good test of this is to find a nice flat stretch of highway and crank it up to 90 or so, then let off the gas and see how quickly your speed drops. 90->70 will come much quicker than 50->30.

Now, the other issue is gearing. "50mph" is NOT the most efficient for all cars. Especially manual transmissions. I used to get much better mileage by skipping up the gears a bit quicker. Cruising at 40 in 5th gear will use less than in 4th. Automatics may not let you do that easily.

As for hybrids, they do not factor in at all in highway driving. They make a difference in stop-start efficiency.

Wheat we NEED in cars now is a 200HP vehicle that gets 40mpg highway, not a 400HP vehicle that gets 20. (I see all these ads for the 500+ HP Caddies and just wonder what old fart really needs that power... IN A LUXURY VEHICLE!).

Meh, reducing the limit to 55 will do little for our situation.

Jolly, just as an experiment... try going 70, but ease off on the accelerator. Try to get out of 1st gear ASAP and get up to 5th even at slower speeds. See what a feather touch on the gas and brakes does for your mileage.

There are plenty of 200 hp cars that get close to 40. There's a reason they aren't huge sellers, people don't want them.

 

[LTC8K6]

http://news.consumerreports.org/cars/2009/09/tested-speed-vs-fuel-economy.html

I'll take these numbers to get there over 2 hours faster.

 

[Linflas]

I endured that bullshit once, I'll pass on a repeat.

 

[overst33r]

See my other post. On paper data charts are assuming (I'm assuming) that your foot is always on the gas. I have to do that when going 55, but not when I'm going ~70. So in the real world, I'm saving gas.

(2011 Altima 2.5)

Very well. FWIW, I've experienced the exact opposite in the 2011 Altima that I rented for 2 weeks, but anecdotal is anecdotal.

1997 was a long time ago, and several of those cars were from well before then.

Cars now routinely have 5 or 6 or even 8 speed transmissions, and much more fuel efficient engines, and probably much more aerodynamic bodies as well.

Sorry I meant Table 4-25. Its is on page 4-26. That data is based on more current (2010) vehicles.

Note: I'm not in favor of a 55mph speed limit. 70mph IMO is the perfect blend of efficiency/time savings. I simply want to clear up confusion regarding 70mph vs 55mph. Many people will argue that their car is more efficient at 70 vs 55, which is false and has been proven time and time again (several links posted in this thread already).

 

[LTC8K6]

The Camry from the example basically got 40mpg at 55 and 30mpg at 75.

That's roughly a 4 gallon fuel difference for a 500 mile trip.

So, I would spend about 13 dollars to get there over 2 hours faster.

Sounds good to me.

And most cars had a smaller difference.

 

[overst33r]

The Camry from the example basically got 40mpg at 55 and 30mpg at 75.

That's roughly a 4 gallon fuel difference for a 500 mile trip.

So, I would spend about 13 dollars to get there over 2 hours faster.

Sounds good to me.

And most cars had a smaller difference.

Agreed.

 

[Perryg114]

I would fall a sleep at 55MPH. To me that is like driving drunk because I would get so bored I would fall a sleep. The best way to reduce CO2 emmisions is to reduce the population. Your car gets better MPH at 55 because of 1/2 the air density times the square of the velocity. That V^2 eats your lunch.

Public transportation is another way to save money on gas. I don't consider that an option until it is manditory for everyone to carry a gun while riding on any form of land transportation. There are too many F-ing idiots out there.

Perry

 

[LTC8K6]

I'll bet sitting in traffic is wasting way more fuel than the higher speed limits.

BTW, the higher speed limits aren't everywhere. Lots of highways are still 55.

 

[fatpat268]

Yea, it's no secret that most cars get their best fuel mileage at ~55. My car (Ford Fiesta) gets around 42mpg if I'm going 55, but I'd rather cruise at 70-75, and there I get ~38mpg. Not a huge enough difference for me to change my habits.

Not only that, driving 55, even while sticking in the right lane, is a lot more dangerous to the other drivers than speeding, so there's that.

 

[HumblePie]

oversteer

It's called an 8 speed Rx8. I get MUCH better gas mileage at 75 than 55. Period.

 

[LTC8K6]

Very well. FWIW, I've experienced the exact opposite in the 2011 Altima that I rented for 2 weeks, but anecdotal is anecdotal.



Sorry I meant Table 4-25. Its is on page 4-26. That data is based on more current (2010) vehicles.

Note: I'm not in favor of a 55mph speed limit. 70mph IMO is the perfect blend of efficiency/time savings. I simply want to clear up confusion regarding 70mph vs 55mph. Many people will argue that their car is more efficient at 70 vs 55, which is false and has been proven time and time again (several links posted in this thread already).

Getting to my destination faster is more efficient. :biggrin:

 

[JJ650]

Really? Once a week I have to drive from DC to Annapolis and I average 70-80 MPH the whole way there and my MPG is at it's absolute best on these trips.

I noticed the same. I get better mileage @ 70mph in my G8 than I do 55-60mph.

 

[overst33r]

oversteer

It's called an 8 speed Rx8. I get MUCH better gas mileage at 75 than 55. Period.

First off, Mazda never made an 8 speed RX8.

Second, have you tried driving steady state at 55 vs 75? Taken sufficient data with a reputable and calibrated instrument (scangauge, etc)?

I've driven a couple of cars with 8 speeds. Both cars I drove shifted into top gear before 55mph when cruising.

Simply stated, the most efficient speed for a car to be is in top gear at the lowest RPM in steady state cruising (obviously without lugging the engine).

 

[LTC8K6]

If your revs are higher, then the conclusion should be obvious...

And your revs are going to be higher...

There's very little chance that anyone is actually getting better economy at 70/75 vs 55/60.

 

[AstroManLuca]

On a trip to Nawlins from Houston, I averaged over 41mpg in my Honda Civic Hybrid going on average 77mph. On my daily commute, averaging about 70mph, I get about 35mpg. I think we should increase speed limits for hybrids.

Then again, on your road trip, you probably did less city driving (as a percentage of total mileage) than you do on your daily commute. I can't say for certain because everyone's commute is different, but I know that every time I take a road trip, my gas mileage goes up because I'm usually burning through a whole tank with 99% highway driving, even if I'm going 70-75 the whole time.

It's really difficult to get an accurate sense of how good your highway mileage is when most people have at least a bit of city driving peppered in. Although I suppose your Civic Hybrid probably has an MPG monitor... the real test would be not to look at your overall average for a road trip vs. a commute, but to only look at MPG while traveling 70 mph vs. MPG while traveling 77 mph. There's no way it could use less gas to go 77 than 70.

But when you start getting up to 50-60 mph, it jumps up in effect quite dramatically. A good test of this is to find a nice flat stretch of highway and crank it up to 90 or so, then let off the gas and see how quickly your speed drops. 90->70 will come much quicker than 50->30.

Isn't that at least partially because of the effect of engine braking too though? Obviously wind resistance plays a part but I know that if I coast to a stop while my car is in gear, it slows down faster if I downshift than if I leave it in 5th gear the whole time. Makes me think that if you start at higher revs, the transmission will slow you down faster.

 

[AstroManLuca]

I noticed the same. I get better mileage @ 70mph in my G8 than I do 55-60mph.

Exactly, because your 55-60 mph commute involves city driving, and you're probably going to the grocery store and running errands on that same tank, whereas on your 70 mph road trips you're hardly doing any city driving at all.

No one has a sense of how good of gas mileage they'd get if they actually drove 55 mph on a road trip because no one wants to spend an extra couple hours driving. To accurately measure it you'd have to fill up at a station near the highway, then drive 55 until your tank is almost out, then fill up again near the highway. Of course going 70 mph with no city driving is more efficient.

 

[overst33r]

Exactly, because your 55-60 mph commute involves city driving, and you're probably going to the grocery store and running errands on that same tank, whereas on your 70 mph road trips you're hardly doing any city driving at all.

Yep. I have a feeling most people that are saying this are using tank averages and not steady state cruising for each speed, which throws the whole thing out of the window.

 

[ShawnD1]

There are plenty of 200 hp cars that get close to 40. There's a reason they aren't huge sellers, people don't want them.

!?!?!?!?
The best selling car in America is the Toyota Camry, and most of them are the i4 models. They have something like 170HP and they get 40mpg (highway) if you don't drive like a retard.

Wheat we NEED in cars now is a 200HP vehicle that gets 40mpg highway, not a 400HP vehicle that gets 20. (I see all these ads for the 500+ HP Caddies and just wonder what old fart really needs that power... IN A LUXURY VEHICLE!).

Old people don't understand horsepower. It's a completely meaningless number to them today because it was a completely meaningless number when they grew up. According to my parents, cars back in the day didn't come with tachometers. That was something you had to get specially installed if you wanted one. You never really knew how fast the engine was spinning. All you had to go by was a bunch of noise, so you had to guess. You don't want to rev the shit out of it and damage the engine, so you change gears at lower rpm and never really hit peak power. The peak power number is meaningless because they would never actually rev the engine to that point. All they know is that the torque number means something because you will operate the car in that rpm range.
As a result, old people look at torque. Something like a Honda Civic Si won't cut it because it only has something like 120lb-ft (but 200HP when it revs to 8k). They need the big V8 that has numbers they saw in the past, 300lb-ft of torque. Of course that also means the engine probably has like 400HP. Back in their day it would only have maybe 200HP because the engine would spin slower or whatever. Some cars in their day actually had larger torque numbers than horsepower numbers. A car would have 200lb-ft but 180HP. All they see is that 200 number. This 200lb-ft Cadillac must be like that old Dodge I owned way back when. In reality, it has twice as much power, does 0-60 in half the time, and it can take corners going twice as fast.

edit:
Having 500HP is part of the luxury experience. In my Toyota Gayolla, passing someone on the highway is nearly impossible. In a 500HP Cadillac, it's as easy as yelling at the TV when that black president is saying something. My brother's Subaru STI only has something like 350HP and that car can pass in the blink of an eye. He doesn't even need to drop a gear. It accelerates faster in 6th gear than my Corolla can in 2nd gear. That is luxury.

 

[skyking]

The ecomodders have proven this time and time again with reams of data to back it up. Not anecdotal stuff, real fuel and mileage logs. I do it when I can but never hold anybody up in the process.
For example, I have a 162 mile (one way) commute at 60 and 70 MPH limits. Same trip, different route is 151 miles at 55 and 60 MPH limits.
I get there about 15 minutes later on the slow road. I am not jockeying for pole position on the interstate with all the assholes and semis, I see as few as a dozen cars total and nobody tailgates. I choose the slow road almost every time.
As a result I go fewer miles and get better MPG, and those 15 minutes are relative bliss IMO.

 

[JulesMaximus]

Wow, so you're saying that my 255hp Nissan Maxima should get at least 40mpg if I only drive 55?

In reality, my car does get better mileage at 55mph than it does at 65-70 but it isn't substantial. Maybe 2-3mpg at best. A Prius would actually be a substantial improvement. My next car will likely be a hybrid or at the very least a fuel sipping economy car.

 

[Red Storm]

The ecomodders have proven this time and time again with reams of data to back it up. Not anecdotal stuff, real fuel and mileage logs. I do it when I can but never hold anybody up in the process.
For example, I have a 162 mile (one way) commute at 60 and 70 MPH limits. Same trip, different route is 151 miles at 55 and 60 MPH limits.
I get there about 15 minutes later on the slow road. I am not jockeying for pole position on the interstate with all the assholes and semis, I see as few as a dozen cars total and nobody tailgates. I choose the slow road almost every time.
As a result I go fewer miles and get better MPG, and those 15 minutes are relative bliss IMO.

Reams of data doesn't fit what I experience in real life. At faster speeds I am able to cruise on the highway, at 55 I need to have my foot on the gas the whole way. Hence, I use more gas going 55. It costs more in both time and money.

 

[AstroManLuca]

Reams of data doesn't fit what I experience in real life. At faster speeds I am able to cruise on the highway, at 55 I need to have my foot on the gas the whole way. Hence, I use more gas going 55. It costs more in both time and money.

Why? Is there something that prevents your cruise control from operating at 55? Or does it have to do with traffic?

Also, have you ever actually measured the amount of gas consumed by a single highway-only trip at 55 vs. at 70?

 

[ShawnD1]

Also, have you ever actually measured the amount of gas consumed by a single highway-only trip at 55 vs. at 70?

Um... yes? My dad and I both do that literally every time. I hit up the gas station near the highway before heading out on a 3 hour drive then I get gas when I reach my destination. Roughly keeping track of gas mileage is a good indicator of how well the car is doing. When my transmission fucked up, gas mileage dropped like a rock.

 

[spidey07]

Why? Is there something that prevents your cruise control from operating at 55? Or does it have to do with traffic?

Also, have you ever actually measured the amount of gas consumed by a single highway-only trip at 55 vs. at 70?

I drive 150 miles, all highway every day. I get best gas mileage at 70-75 Mph of 32mpg. 80 and it drops to 31.7-.9 I am guaranteed to drop below 30 if I go 55-60 mph. I'm measured it many times. Has to do with gearing. 55-60 is in between gears for best efficiency.