Free Ebook.


Enter your email address:

Delivered by FeedBurner

« When to Buy versus When to Rent | Main | Posts of the Week -- July 14 »

July 14, 2006

Comments

Feed You can follow this conversation by subscribing to the comment feed for this post.

My opinion is that too much speed is not worth it (tickets), but a little bit of extra speed is worth it. I usually travel at 5 to 10 MPH over the limit, and I have never had an indication from either my car or my wife's car that the speed is causing any negative impact on the gas mileage. It is other driving habits, such as tailgating, jackrabbit starts, etc, that determine your gas mileage. In fact, my wife sees about 28-30 MPG while driving her car, and I see about 32-34 MPG - using the same top speeds of 5-10 MPH over.

The truth is, it's much more likely that you'll be tailgating (and hence speeding up/slowing down more often) if you are going over the speed limit, and I think that's the real reason that some people see MPG drops by going faster. I see the exact same mileage traveling at a constant 75MPH as when I'm traveling at a constant 65MPH, and I get there just a bit faster.

I'd have to agree. I've been putting 300+ extra miles on my car every weekend this spring and summer, and I haven't really noticed a drop in mileage, in fact, it's gone up to 30mpg overall from about 27mpg over the winter. That's going about 70mph on my long haul drives. I tried going the speed limit (variously 50-65mph in spots) and I didn't get nearly 70mph then.

It really depends on the driver and their acceleration more than anything. Lots of people like jackrabbity starts. I think the difference is that on my long haul drives, I don't stop and go. I accelerate once to get moving, and never come to a complete stop for toll booths now that I have one of those electronic toll passes.

My wife and I recently took a road trip of around 1400 miles. We tracked gas milage, distanct and time to get an average speed vs. milage relationship.

Our car insurance doesn't count out of state tickets that aren't reported, nor do they care if we get one or two a year (we have a good agent), so once we get out of our home state, our speed goes up. We also budget the occasional ticket into our expected travel expenses. Recently, we've been lucky and haven't had to use this fund.

Our car is a standard V6 sedan with automatic transmission. On one tank, we averaged 68 mph over mostly steady interstate traffic - not much slowing or speeding up and made 31 mpg. One open two lane highway (one in each direction) we averaged 30 mpg driving 73 mph. My wife has the real lead foot - on another stretch she managed to knock us down to 26 mpg and we averaged 87 mph. This also had a little slowing and speeding up as we overtook cars on the highway.

And the best stretch, we were passed on the highway by and SUV like we were standing still, so we let them get about a quarter mile ahead of us and paced them - 100+mph over a 100+ stretch of road. Average speed for the section - 95 mph @ 21 mpg. This was all done on the same day on the same octance fuel (not the same brand) so I hope that there were no other large factors. The wind was light (no 25 mph in either direction at any point).

So, at 65 to 75 mph, we don't see a large difference. At 85+ mph, we see one, and at the mid 90s, the air resistance makes a huge difference.

1400 miles at 73 mph = 19.2 hours.
1400 miles at 30 mpg at $3/gal = $140.

1400 miles at 87 mph = 16.1 hours.
1400 miles at 21 mpg at $3/gal = $200.

Granted, we can't average these exact speeds over the entire distance with varied roads and time of day (we slow down when it's dark so we don't overdrive our headlights) but I will spend $60 to save three hours in a car, especially on a trip of this length.

It's not about being a math wizard. The studies referenced claim that speeding makes it feel like you're getting there faster, while actual net time saved is not as great as you'd think. As GHoosdum pointed out, you tend to speed in spurts, so unless you're flying down I-5, driving time is not as simple as dividing distance by mph.

The point of the studies is to show that while people claim they speed because they like to 'get places more quickly,' speeding doesn't actually reduce their driving time as much as they perceive that it does. More accurately, people speed because it feels more fun and more productive to go fast. And hey, I'd pay 60 bucks for a more fun and less frustrating road trip.

The studies mentioned that claim speeding merely makes it feel faster have obviously never driven through rural Wyoming and South Dakota. While it is nice to be out of the city and on open roads, no speed will make hundreds of miles of flat straight road feel like it's going by fast.

But if you want to know what slow feels like, try driving 100+ mph for an hour and a half and then slow down to 35 mph to drive through a town. I felt like I could jog that fast.

Often, if in a hurry - though I hesitate to ever be in a hurry, because after all - if you never get there due to wrecklessness, it probably won't amount to much in the long run.

Anyway, I use the 10% rule - if in a hurry. If the limit is 70, I try to limit my maximum speed to 77 mph. If 40, then no more than 44mph (or 45mph). When not urgent, I keep the speed at the limit generally speaking.

Utilizing the cruise control as often as I can as it seem to be the most efficient way to use the engine and keep a constant speed.

We drive an '02 Prius. The display calculates mileage every five minutes as well as mileage as it drives by the tank. The biggest thing that negatively affects mileage is headwind. The engine / motor combination is efficient enough that mileage only varies from a low of around 42mpg to 44mpg (per tank) in average conditions whether we drive 70, or 77mph.

A strong head wind has cut mileage down to just under 37mpg in the worse case since we have been driving it (2/2006).

In my experience, speed has little to do with how quickly I get somewhere (So why don't I slow down ;-). On a short trip, you just aren't going far enough for 5 or 10 mph to make an appreciable difference. On a long trip, the number of stops (gas, food, rest areas) have a huge effect in relation to speed.

Nonetheless, being from Montana, where the speed limit used to be "reasonable and prudent", I have a hard time slowing down.

In my experience the idea that 55MPH gives you the best miles per gallon is a myth. The actual "Sweet Spot" speed varies from vehicle to vehicle, and actual savings from hitting that sweet spot varies as well. Bigger vehicles benefit more from not speeding (and the risk of rollovers makes keeping the speed down more important on bigger vehicles)

I like to speed when there's open highway with no or few cars ahead of me. But that's mostly just interstate driving. I cap my speed off the interstate at 10 over the limit (assuming its a 55 zone) and that's even assuming that the road is empty.

I like cars that have meters that show your recent miles per gallon. It acts as a good way of really learning what driving behaviors save on gas. You learn to take advantage of hills for acceleration / deceleration, and do a lot more coasting.

No need to race to the next red light, just let your momentum carry you (unless you're tying up traffic). The same if there's a group of cars up ahead going slower, you'll link up with that conga-line soon enough.

Why do I feel like I'm the only guy left in America that drives 55? I used to hang out at junkyards. I've seen what excessive speed can do to a car.

Is anyone factoring in the cost of safety here? Speed limits are based on safety, and there is nothing more expensive than winding up smeared all over the interstate.
No matter how good a driver you are, exceeding the speed limit increases your chances of getting into an accident, and also increases the chances that an accident will be fatal.
The faster you are driving, the less time you have to react appropriately to unexpected circumstances.
Bottom line: Speeding is expensive. Tickets, gas, and the potential for catastrophe all contribute to the reason why most people should just leave the damn house a little sooner.

Rant On: Let's face it, no one thinks "their" speeding is a problem. Yet open your newspaper any day of the week and read about the death of people or deaths caused by people who didn't think their speeding was a problem, most all of the cases will involve speeding or speeding associated actions (e.g. how many times have we all felt the guy in front of us was going too slow, so we've begun to tailgate and then pass at the first possible opportunity, even when it wasn't the safest). My deal is that I'm comfortable slightly above the typical speed limit, but anyone driving at or near the limit is within their rights to do so. Threatening them with 2000+ pounds of metal and plastic is like walking behind someone with a shotgun pointed at their back. "You can trust me, I've got the safety on." So I no longer tailgate when I come up on someone driving slower than I'd like and I take a deep breath and don't get upset and either let it go or wait for a safe opportunity to pass. Eventually I'll get there and over a few miles does getting there 30 seconds sooner really make a difference?

Also, please keep in mind speed limits on most roads are not just based on how fast you can go down a roadway without sliding into a ditch. They also include things like type of neighborhood, stopping distances and how far ahead you can see. So as a little food for thought, how fast do you want others driving through your neighborhood and around your children, friends, or family? Set the example in your neighborhood and extend the curtesy when you're in someone elses.
Rant Off

With respect to gas milage, I've found that within ten miles an hour on the highway keeping a constant speed seemed most important with respect to gas usage. So if traffic is going slower, it's usually easier to go with the flow instead of constently running up on someone and having to slow down then accelerate again. Obviously with a fairly open highway you can pick the speed you think your car does best in and use the cruise control. I also found that with a long highway haul, filling up the tank with the higher octane gas extended my milage, though I don't notice that in town/city driving. I don't know that the cost is necessarily worth it but it can keep me from having to stop as often for a fill up and that can potentially save more time than driving faster. In town or city, it's the pedal to the metal jackrabbit starts that seem to suck gas. I've always been of the opinion that a brisk acceleration is best since there is a time component as well in the acceleration equation so it's a balance between the jackrabbit start and sucking gas with a long, drawn out acceleration. Just my two cents worth.

Rant On: Let's face it, no one thinks "their" speeding is a problem. Yet open your newspaper any day of the week and read about the death of people or deaths caused by people who didn't think their speeding was a problem, most all of the cases will involve speeding or speeding associated actions (e.g. how many times have we all felt the guy in front of us was going too slow, so we've begun to tailgate and then pass at the first possible opportunity, even when it wasn't the safest). My deal is that I'm comfortable slightly above the typical speed limit, but anyone driving at or near the limit is within their rights to do so. Threatening them with 2000+ pounds of metal and plastic is like walking behind someone with a shotgun pointed at their back. "You can trust me, I've got the safety on." So I no longer tailgate when I come up on someone driving slower than I'd like and I take a deep breath and don't get upset and either let it go or wait for a safe opportunity to pass. Eventually I'll get there and over a few miles does getting there 30 seconds sooner really make a difference?

Also, please keep in mind speed limits on most roads are not just based on how fast you can go down a roadway without sliding into a ditch. They also include things like type of neighborhood, stopping distances and how far ahead you can see. So as a little food for thought, how fast do you want others driving through your neighborhood and around your children, friends, or family? Set the example in your neighborhood and extend the curtesy when you're in someone elses.
Rant Off

With respect to gas milage, I've found that within ten miles an hour on the highway keeping a constant speed seemed most important with respect to gas usage. So if traffic is going slower, it's usually easier to go with the flow instead of constently running up on someone and having to slow down then accelerate again. Obviously with a fairly open highway you can pick the speed you think your car does best in and use the cruise control. I also found that with a long highway haul, filling up the tank with the higher octane gas extended my milage, though I don't notice that in town/city driving. I don't know that the cost is necessarily worth it but it can keep me from having to stop as often for a fill up and that can potentially save more time than driving faster. In town or city, it's the pedal to the metal jackrabbit starts that seem to suck gas. I've always been of the opinion that a brisk acceleration is best since there is a time component as well in the acceleration equation so it's a balance between the jackrabbit start and sucking gas with a long, drawn out acceleration. Just my two cents worth.

The comments to this entry are closed.

Start a Blog


Disclaimer


  • Any information shared on Free Money Finance does not constitute financial advice. The Website is intended to provide general information only and does not attempt to give you advice that relates to your specific circumstances. You are advised to discuss your specific requirements with an independent financial adviser. Per FTC guidelines, this website may be compensated by companies mentioned through advertising, affiliate programs or otherwise. All posts are © 2005-2012, Free Money Finance.

Stats