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What Can A 15 MPH Difference Do To Affect FE?

  #1  
Old 06-25-2006, 11:09 AM
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Default What Can A 15 MPH Difference Do To Affect FE?

I took a ride yesterday that I've taken many times in the past. 215 miles one way. I usually do it at a cruise control speed of 70 mph. I pretty much always get 37 mpg on the dash, FCD, and by hand. Consistently.


Yesterday, I did it at 85 mph (75 mph speed limit). At the end of the 215 miles, my dash readout was 32 mpg.


So, I lost 5 mpg over the course of my three hour drive. It normally takes me three and a half hours, so I gained 30 extra minutes.

215 miles / 37 mpg = 5.81 gallons X $2.84 = $16.50 for this leg at 70 mph

215 miles / 32 mpg = 6.72 gallons X $2.84 = $19.08 for this leg at 85 mph

So, I only spent an extra $2.58 to gain 30 minutes. I feel that's money well spent! Heck yeah! I'd spend an extra $5 a day to gain an hour of free time. Sure, why not! Especially on really fun days! I can't tell you how many times I've been out with the family and friends to some place such as Busch Gardens. We're all having a ball! But then it comes to closing time. I'd gladly throw down and extra $10 just to have two more hours to spend with my gang.


But, I digress...

Sure, I gained an extra 30 minutes. But, I didn't need it. I actually got to my destination a whole hour early. So yeah, $2.58 isn't much money to be saving. So I can't say I drive slower because I want to save money. Hell, I've wasted a LOT more than $2.58 on my daily spending. Did I really need that $3 coffee? Or how about that $5 magazine? Or even the amount of money I waste on satellite TV? (sidebar: prior to getting married, I didn't even own a TV. And even if I did, I'd be happy with broadcast.) I generally make this trip once a month. That comes out to $61.92 in gas savings per year. I've probably lost more than that in errant loose change in the couches I've sat in over the past year. So this brings me to why I DO drive slower.

The added effort to be continuously monitoring for the "holes" in traffic to maneuver through just wasn't worth the time savings. I much rather drive at 70 mph and just let traffic whiz past me. It's much more relaxing. I just set the cruise, pick a station on XM, and drive.

Off topic 1: on my trip yesterday, I was on I-10 East of Tucson by maybe 20 miles. This is a 75 mph road, four lane divided. Some HCH was traveling in the right lane going MAYBE 45 mph!! Cars were bottlenecked behind this knucklehead, trying to get around. As I pass this HCH, I saw some dude who looked to be about 70 years old. He had one of those wraparound sunglasses which fit over eye glasses, and a baseball cap, and was hugging the steering wheel like Mr. Magoo. I mean, his face must have been mere inches away from the steering wheel! I can't imagine the kind of damage the airbag would do to his face if it deployed.


Off topic 2: on my way back home yesterday, I was driving on the same stretch of I-10. Now, it's dark out. I was approaching an SUV pulling the smallest trailer U-Haul has to offer. He was probably doing about 50 mph and driving with his flashers on. On this particular part of the highway, it's pretty hilly. Usually, semi trucks will drive around 50 mph so they can climb small grades of 6%. These hills are definitely less than a 6% grade. If I had to guess, I'd say at most 4%. And semi's don't generally slow down for these slight rolls. But this SUV, a Mitsubishi Montero, which has something like a 4,000 pound towing capacity (?) and pulling maybe up to 1,500 pounds (that trailer has something like a 1,000 pound load capacity), and the driver thinks he needs to do 50 mph to make it up those hills? So, either there was a bigger issue at hand, like he was trying not to spill his mocha latte, or he really thinks his truck can't handle his load. I guess it really didn't bother me that he was doing this, just confused me. I've known people that would think like that. Think their vehicle can't do something, when it was definitely designed to do just what they're trying to do. And I've known the completely opposite. They'd try to do something, like haul an 8,000 trailer with a truck rated at 2,000 pounds, and then call their vehicle a piece of crap when it breaks because of it.
 
  #2  
Old 06-25-2006, 11:25 AM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

One of the first lectures in an econ class is about opportunity cost. Everything- material or action- has a dollar cost associated with it. If you gotta get there fast, the cost is extra fuel. If you don't gotta get there fast, the cost is extra time on the road. Which cost is less "costly" depends on the person and situation.

You've done 70 and 85- care to try it at 55? I notice a large upswing dropping from 65 to 60 to 55, and it seems to level out there, since lockup is at 48 anyway.
 
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Old 06-25-2006, 11:32 AM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

Don't forget the $250 ticket for going 20-30 over the posted limit.......plus the added risk of a fatal crash going 85 in a compact car.....
 
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Old 06-25-2006, 11:54 AM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

20-30 over the speed limit?? I was doing 10 mph over.
 
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Old 06-25-2006, 11:57 AM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

Originally Posted by bar10dah
20-30 over the speed limit?? I was doing 10 mph over.
$156 ticket (non-construction zone, non-school zone), in that case, in TX anyway. Plus $5 for each additional MPH over the posted limit. Add in the cost to get a single "minor" speeding ticket dropped from one's insurance in TX (if your record's clean) by taking driver's (re-)education, and it's even more expensive.

Yes, I know from experience. I got pegged at 43 MPH in a 30 MPH in front of a police substation last summer... in my '92 Corolla. The cops usually tailgate you if you're going 40 mph, but that's a moot point when there's an officer outside your window with your I.D. in hand.
 

Last edited by GeekGal; 06-25-2006 at 01:10 PM. Reason: Memories...
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Old 06-25-2006, 01:01 PM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

Driving faster does save time but it costs more than just gas. Since driving faster might get you a ticket, there is a cost in stress even if you don't get a ticket. Besides the cost of gas you pollute less when driving slow, an additional benefit. Surely driving slower is more safe, to a point anyways. Then there is wear and tear on the car and tires.....
 
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Old 06-25-2006, 06:31 PM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

A lot of the U-Haul trailers used to be rated at no more than 45 mph. Don't know if they still are or not. I would imagine they rate them according to the axle/wheel construction. So doing 50 mph may have been the Montero driver's way of travelling at about the safe speed of the trailer.

So far as the old guy doing 45, well, if he's got a drivers license and the minimum speed is 45, he's not breaking the law. Going 80 in a 70 mph speed zone is. Not meant to be critical - just the facts.
 
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Old 06-26-2006, 08:15 AM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

At the same time, I sympathize with bar10dah about the old person driving slow. I do not mean disrespect to this elderly gentleman or to any elderly person who chooses to drive slow. But when there comes an age when it becomes difficiult to make decisions behind the wheels, then, people should get some help. Let their children or their care-takers drive them around. It is hazardous to drive that slow on a highway, besides irritating many other drivers.

I remember going on Hwy 21 between Bastrop and San Marcos (close to Shannon's San Antonio .. so she might know what I am talking about). It was a one lane road, and I could not pass the vehicle in front of me which had an elderly couple driving at 20 mph on a 65 mph highway. The road divider indicated that I could not overtake vehicles on that stretch of the road. Despite the norm of that section of highway having very little traffic (I would say 2 cars passing per minute at a given point on that road), we were stuck long enough behind this slow car for about 10 cars to be trailing behind us .. forming a srot of caravan. Can you imagine the frustration that the drivers (and the passengers) of those 10 cars had to go through because of one slow driver?

When at last, I did get a way around him (I do not remember whether the one lane highway gave way to 2 lanes), or the road-divider sign indicated that overtaking was allowed, I let out a sigh or relief. My wife was laughing at me when I did that .. I mean, it was just ridiculous out there. Although we could hold our frustration up, not everyone in that long caravan of cars did .. they honked and screamed at them, which made me feel bad for the elderly couple ...

I think, a fair suggestion and a good compromise would be that the elderly couple still go around, but dont drive themselves ...
 
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Old 06-27-2006, 05:48 PM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

I also sympathize with bar10dah and with you, kamsmart. I don't like getting behind people travelling 45 mph on the interstate either. And the person travelling 20 on the highway, if caught, would likely get a ticket for obstructing the flow of traffic, I believe.

But I would rather see someone driving 45 on the interstate than someone plowing past me at 90. I feel that the latter driver is more of a hazard to me than the 45 driver.

Kamsmart, I have to take issue with your statement that driving 45 mph on the interstate is hazardous. If it were hazardous, the states would not set the minimum speed there. IMO it is the people who are impatiently trying to dodge around that driver, or who come up behind that person either exceeding the speed limit or not watching road conditions that cause the hazard. Just my opinion.
 
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Old 06-27-2006, 09:54 PM
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Default Re: What Can A 15 MPH Difference Do To Affect FE?

Originally Posted by kamsmart
I remember going on Hwy 21 between Bastrop and San Marcos (close to Shannon's San Antonio .. so she might know what I am talking about). It was a one lane road, and I could not pass the vehicle in front of me which had an elderly couple driving at 20 mph on a 65 mph highway. The road divider indicated that I could not overtake vehicles on that stretch of the road. Despite the norm of that section of highway having very little traffic (I would say 2 cars passing per minute at a given point on that road), we were stuck long enough behind this slow car for about 10 cars to be trailing behind us .. forming a sort of caravan. Can you imagine the frustration that the drivers (and the passengers) of those 10 cars had to go through because of one slow driver?
I am familiar with that stretch of roadway, although I have not yet driven it in my hybrid (too darned hot for most of my trips to parks to hike and camp).

My problem locally (San Antonio) is the opposite, at least right now. The roadway will be pretty clear. It'll be very early morning or 10-11 PM at night. I'll be driving the speed limit or 5 under it in the right-most lane. Suddenly, I've got a speed demon racing up my tailpipe and whipping around at the last second, as though I should have moved into the left lane to let him/her pass. It's enough to make me go a little nuts, between these and the oblivious drivers who don't recognize simple physics. I'm getting tired of hearing tires squeal behind me because someone ignores my brake lights (if I'm following a vehicle that's turning) and/or my signal and brake lights (if I'm the vehicle making the turn).

And cops... don't get me started about cops. Pleasant drive this evening (barring the above) until a cop car redlines, roaring its engine while passing me on the left, only to squeal his brakes as a red light brings him to a stop behind another vehicle. He'd have run the light if he hadn't had a pickup in front of him... Grrrr....
 

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