Found another way to save on gas.

[Compaq888]

Well since I pumped up my tires I have been finding myself going faster than other drivers and that caused me to use the #2 lane which is the second lane from the left. Sometimes even the #1 lane. Since I pumped up the tires I'm now thinking my speedo is wrong. Since my tires are different now and are pumped up that means I'm actually going faster than what my speed says. Since I always drive 65mph on the freeway in reality i'm going 66-67mph. Not only do I gain a couple mpg by pumping up my tires but if I reduce the speed to 63mph I will be even saving more fuel because my sweet spot is 55mph. Not only that but i'll really be going 65mph. No point in speeding if there are too many benifits of going the speed limit.

Here play around with this...
http://www.miata.net/garage/tirecalc.html

[CosmicMC]

So have you actually measured the change in your tire diameter and its effect on your speedometer since increasing the air pressure, or is this pure speculation and guesswork?

What if you go the speed limit on the highway while nearly all other cars are exceeding it by 15 MPH, and because of some careless driver who's speeding, an accident occurs because she tries to make a lane change to avoid rear-ending you and side-swipes a minivan. How much gas is wasted cleaning up the mess, fixing the vehicles, transporting the injured to a hospital, investigating the accident, paying the insurance claims, etc.? How often do such accidents occur? If it costs you an additional $2.00 in gas for your trip to drive at roughly the same speed as almost everyone else who's speeding, was it worth the $2.00 as insurance against an accident? Most police officers on traffic duty will not issue you a ticket if you're speeding but keeping up with traffic around you, as long as your speed isn't too ridiculously high.

[SVOboy]

So, you're saying that we should speed to keep up with everyone else then? If you wanna play the safety game you can get all sorts of data about reaction times and safety as you go from 65 to 80 mph, not to mention the fact that most cops will not let you off speeding 15 mph unless they also enjoy spending their time cleaning up after crashes.


EDIT:
http://safety.fhwa.dot.gov/speed_manage/docs/speeding_facts.pdf

Speeding causes 1/3rd of all crashes? Speeding costs 27.7 billion dollars per year? Speeding causes almost as many fatalities as drunk drunk? Most speeding fatalities happen on the highway? Huh? Is it just me?

[Matt Timion]

Originally Posted by SVOboy

So, you're saying that we should speed to keep up with everyone else then? If you wanna play the safety game you can get all sorts of data about reaction times and safety as you go from 65 to 80 mph, not to mention the fact that most cops will not let you off speeding 15 mph unless they also enjoy spending their time cleaning up after crashes.

ACtually, in Southern California (where Compaq888 lives) they do. 80mph is normal "flow of traffic." The only people going 65mph are the semis.

His initial question however is valid. Did Compaq888 take measurements and determine the actual increase of his tires and make a calculation (or even a regression line) determining how much his speedometer was off, or was his change in speed all based on gut feeling?

[SVOboy]

80 mph is the flow of traffic in my area too, but people still get pulled over left and right.

[Compaq888]

Originally Posted by CosmicMC

So have you actually measured the change in your tire diameter and its effect on your speedometer since increasing the air pressure, or is this pure speculation and guesswork?

What if you go the speed limit on the highway while nearly all other cars are exceeding it by 15 MPH, and because of some careless driver who's speeding, an accident occurs because she tries to make a lane change to avoid rear-ending you and side-swipes a minivan. How much gas is wasted cleaning up the mess, fixing the vehicles, transporting the injured to a hospital, investigating the accident, paying the insurance claims, etc.? How often do such accidents occur? If it costs you an additional $2.00 in gas for your trip to drive at roughly the same speed as almost everyone else who's speeding, was it worth the $2.00 as insurance against an accident? Most police officers on traffic duty will not issue you a ticket if you're speeding but keeping up with traffic around you, as long as your speed isn't too ridiculously high.

I'll be blunt as possible. If somebody is speeding that is their problem, not mine. If they hit that minivan that is their problem.

I'm going the speed limit for several reasons and they are:
*to save on gas
*Avoid tickets
*the slower you go the faster you can stop. On my car if I were to slam on brakes at any speed it locks up. So if I'm going like the rest of the ape **** on the freeway at 80-85mph my chances of getting into a wreck is higher than going 65mph. My brakes lock up because I don't have ABS and the dealer says it's normal for my car.

And most police officers will issue you a ticket. When i got into a wreck with my last car I was going 8-10mph over the speed limit and the wreck wasn't even my fault. The cops started hassling me that I was speeding and the whole thing was my fault. Some witnesses walked up and said that somebody else was at fault and ran away. So they forgot all about the my fault thing.

Next is the tire diameter thing. I'm not speculating nothing. I checked it by measuring everything.

I'm not like everybody else. I don't speed just so I can make it somewhere faster. If everybody is going to jump off the bridge I'm not going to join them.

[CosmicMC]

Compaq888, so, since you checked it by measuring everything, what was the diameter change in the tire that you measured before and after overinflating the tires? What did you use to take the measurement? I'm asking because you're citing a 3.1% change in speed and that seems excessive to me for a few more PSI in the tires. Without the numbers, though, it's purely speculation on my part. Please educate me, as I am ignorant of the possibilities here.

As far as the speeding part, I never suggsted anyone should exceed the speed limit. I posed a hypothetical situation and asked a question about whether it's worth it to speed to keep up with the flow of traffic instead of impeding it and potentially causing an accident. I never said it would be more fuel-efficient overall. I was asking a series of questions and so far nobody has offered any answers but SVOBoy is trying to imply that I'm crazy for making a statement that I never made. It probably sounds like I'm leaning in one direction or the other, so shame on me for not wordsmithing my post more effectively.

So there are no answers so far. The question stands: Is less fuel consumed overall if you speed to keep up with traffic instead of driving the speed limit when everyone around you is speeding? Need someone with statistics on that one.

[diamondlarry]

What if you go the speed limit on the highway while nearly all other cars are exceeding it by 15 MPH, and because of some careless driver who's speeding, an accident occurs because she tries to make a lane change to avoid rear-ending you and side-swipes a minivan. How much gas is wasted cleaning up the mess, fixing the vehicles, transporting the injured to a hospital, investigating the accident, paying the insurance claims, etc.? How often do such accidents occur? If it costs you an additional $2.00 in gas for your trip to drive at roughly the same speed as almost everyone else who's speeding, was it worth the $2.00 as insurance against an accident? Most police officers on traffic duty will not issue you a ticket if you're speeding but keeping up with traffic around you, as long as your speed isn't too ridiculously high.

I have a problem with this logic. I drive the speed limit. PERIOD! If someone has a problem with me OBEYING the law, then it's just that; their problem. A few years ago there was an incident in another town near me where there were riots for about two days because a man on a motorcycle was killed while running from the police after he had committed a crime. The people were rioting because the police were doing their job and enforcing the law when the man was killed. They started coming up with the goofy idea that police shouldn't chase someone if they ran after committing crimes. So just to protect the criminal's life they should just let him go. The same or similar thing applies to the idea that you should stay with traffic even if it is going 10-15 mph over the limit. I agree with what SVOboy says:

So, you're saying that we should speed to keep up with everyone else then? If you wanna play the safety game you can get all sorts of data about reaction times and safety as you go from 65 to 80 mph, not to mention the fact that most cops will not let you off speeding 15 mph unless they also enjoy spending their time cleaning up after crashes.

EDIT:
http://safety.fhwa.dot.gov/speed_manage/docs/speeding_facts.pdf

Speeding causes 1/3rd of all crashes? Speeding costs 27.7 billion dollars per year? Speeding causes almost as many fatalities as drunk drunk? Most speeding fatalities happen on the highway? Huh? Is it just me?

Do we become part of the problem of speeding by "keeping up traffic" and contributing to increased accidents and death, or do we become part of the solution and drive the speed limit which saves lives and gas? If everybody followed the rules, there wouldn't be any "keeping up with traffic." Sorry about the long windedness but it kind of bothers me.

[SVOboy]

So there are no answers so far. The question stands: Is less fuel consumed overall if you speed to keep up with traffic instead of driving the speed limit when everyone around you is speeding? Need someone with statistics on that one.

The government (which I think has had some experience with cars) says <a href=http://www.fueleconomy.gov/feg/driveHabits.shtml target=_blank> this</a>:

While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph.

As a rule of thumb, you can assume that each 5 mph you drive over 60 mph is like paying an additional $0.21 per gallon for gas.

Observing the speed limit is also safer.

[MetroMPG]

the question of go with the flow or not is a good one.

i started its own thread here