so i was doing some thinking today on my way home since i started driving 65 rather than 70if i can gain 2mpg by doing 65 rather than 70 mph i will save (fuel at $4/gal) 3 cents a milei will use my situation.. Drive: 70 miles/day 20 days/month 1400 miles/month x .03 cents = $42now saving $42 a month doesn't seem like much but lets look at how much more time it takes for me to drive 70 miles a day at 65mph vs 70mph60min/70 = .857143 minutes/mile x 70 miles = 60 minutes of driving per day60min/65 = .923077 minutes/mile x 70 miles = 64.6 minutes a dayso if i save myself 5 minutes round trip thats 2.5 minutes per one way so really unnoticeable as far as fuel savings by driving slower and time savings by driving faster (5 minutes versus $2)heres where it gets interesting... if i look at that as dollars an hour i can take (2x12)/(5x12) = $24/60min:smart:so by driving 65 miles an hour rather than 70 if i look at it as time spent for the money saved im making 24 dollars an hour just for driving 5 mph slower...what a deal!also..im in the process of checking my exact mileage gains but say i get 4mpg more then everything doubles+2mpg = $24/hr+3mpg = $36/hr+4mpg = $48/hrnow as fuel prices go up... so does your money making!!:cookoo:i always like to look at the positive side of things:thumb1:

Start looking at going 45- or 55.... The savings I thinking on our trucks is about 45-50 I believe that is what MoparMan says.

lol... well im not going to go that farim already below the speed limit for normal traffic by 5mph at 65 and above michigans commercial truck limit by 5 (dont ask me why they do that because its rediculous)maybe id find a semi and draft at 60-65 depending on his speed but im talking about driving on a freeway not the regular 2 lane highway otherwise yes i'd go 55-60 rather than 65-70im going to see what this weeks fuel tank brings me and if its not more than 2 mpg i'll try drafting semis next week lol:neutral:

My top speed is 55 MPH but I'm now getting 23-24 MPG as the weather warms up. Still have my winter front on and my MPG fooler going. In Idaho there is no minimum speed limit so if I wish to drive 55 MPH in a 65 MPH zone no one can say word including law inforcement. The only rule I must adhere to is if I'm holding up more that 3 vehicles I must yeild to traffic flow. From experiementing around here I found the best speed gear combo is 45 MPH in 4th Gear (1:1 Ratio) (~1,900 RPM) with 3.55 gears will get you really close 30 MPG. But that is way to slow for my blood.

On my hunting trips and other cruises, I usually keep it at 65mph. I find it stressful driving when your trying to go 75mph by weaving in and out of slower traffic. I just let most everyone pass me now. And now with fuel prices rising, the idiots out there driving 80+mph will be the first to _____ and moan about fuel prices!!!!:doh:I've also found the the 65ish mph up to about 2k rpm's is the sweet spot on my truck. I have no doubt that I could get better mileage driving 60 or 55, but I've found that at those speeds in 6th gear, I actually have higher EGT's than at 65mph. That's cruising level ground. If you talk with any old time truckers, they often drove by the EGT. AH64ID may have a good answer for that??

I guess I'm lucky really... Most of the state has 65 MPH roads out here except for the 2 interstates highways I-90 and I-84 which are 75 MPH. Now most of all the roads around me ar 45-55-65 MPH. Then since most of the state is nothing more that windy roads through canyons this give more excuse to cut speed. 55-60 MPH is really comfortable and relaxing. Kind of waiting for ISX to dive in on this thread...

I guess I'm lucky really... Most of the state has 65 MPH roads out here except for the 2 interstates highways I-90 and I-84 which are 75 MPH. Now most of all the roads around me ar 45-55-65 MPH. Then since most of the state is nothing more that windy roads through canyons this give more excuse to cut speed. 55-60 MPH is really comfortable and relaxing. Kind of waiting for ISX to dive in on this thread...

You just had to pull me in here didn't you! I have experimented with different speeds for years. Driving to college and back every weekend for 2 years and driving to work and back on a 65mph 4 lane gave me a lot of time on my hands (college was 90 mile trip, work is 40 mile). I was trying to get better mileage or figure out how much each speed yielded. I went from 70 down to 45mph. I got 27 at 55, wasn't able to do 50 or 45 long enough to tell with that. I did do 45mph all winter for a tank and got 24mpg, but this was when it was 10F and it was actually so slow and so cold that I would never break 170F or even ever open the thermostat, the heater was taking all the heat. So I believe 55 is fast enough to get there and slow enough to get good mileage. There is something else I didn't realize until I did this testing. When you are on a 4 lane that you drive 65-70-75+mph on, just as Dorkweed said, you gotta pay attention and weave through traffic and all this other crap, it sucks. Now the 4 lane I was on didn't really have many people but at 55 on a road meant for 65, you could basically do anything you wanted in the truck and not have to worry about the road. You don't have to hold the steering wheel as tight and attentive. When I did 45 last winter, I loved it. No care whatsoever on what was behind or in front of me since it was coming up so slowly. I turned the radio up and kicked back and turned the heat all the way up until it was equivalent to a 90F day at the beach. Ever since that realization, I rarely break 60, I don't even remember ever breaking it. I don't like the way my truck sounds at 70mph anyways. That high in the RPM with no load just sounds the same as free revving it. It sounds perfect with a trailer or any kind of load, but the truck by itself isn't enough to strain the engine once it gets above 65mph since it is so high in the RPM so it just kinda sounds a little mad. I pull the trailer at 70, it likes it there for some reason, the inertia keeps the mileage up. My brothers dakota is a different story. I hold it to the floor all day long. It is so small that it's not like it takes any effort to drive it whether your going 10mph or 100mph.

You just had to pull me in here didn't you!

I have experimented with different speeds for years. Driving to college and back every weekend for 2 years and driving to work and back on a 65mph 4 lane gave me a lot of time on my hands (college was 90 mile trip, work is 40 mile). I was trying to get better mileage or figure out how much each speed yielded. I went from 70 down to 45mph. I got 27 at 55, wasn't able to do 50 or 45 long enough to tell with that. I did do 45mph all winter for a tank and got 24mpg, but this was when it was 10F and it was actually so slow and so cold that I would never break 170F or even ever open the thermostat, the heater was taking all the heat.

So I believe 55 is fast enough to get there and slow enough to get good mileage.

There is something else I didn't realize until I did this testing. When you are on a 4 lane that you drive 65-70-75+mph on, just as Dorkweed said, you gotta pay attention and weave through traffic and all this other crap, it sucks. Now the 4 lane I was on didn't really have many people but at 55 on a road meant for 65, you could basically do anything you wanted in the truck and not have to worry about the road. You don't have to hold the steering wheel as tight and attentive. When I did 45 last winter, I loved it. No care whatsoever on what was behind or in front of me since it was coming up so slowly. I turned the radio up and kicked back and turned the heat all the way up until it was equivalent to a 90F day at the beach.

Ever since that realization, I rarely break 60, I don't even remember ever breaking it. I don't like the way my truck sounds at 70mph anyways. That high in the RPM with no load just sounds the same as free revving it. It sounds perfect with a trailer or any kind of load, but the truck by itself isn't enough to strain the engine once it gets above 65mph since it is so high in the RPM so it just kinda sounds a little mad. I pull the trailer at 70, it likes it there for some reason, the inertia keeps the mileage up.

My brothers dakota is a different story. I hold it to the floor all day long. It is so small that it's not like it takes any effort to drive it whether your going 10mph or 100mph.

Yes I did because I knew the bold text would come out... This is exactly what I enjoy here in Idaho there is very little traffic on the highways out here so 55 MPH is a very comfortable pace and enojyable experience...

Thank You ISX for your words here!

I actually never care what traffic is like. I have held up 20 cars on the 2 lane highway going 55 in a 60 for 90 miles. Half of it is 4 lane so they could all pass me eventually. But the speed limit does not mean you have to run it IMO. My trucks limit is 3000RPM and I don't run that.. In theory, if there is a minimum and a maximum speed limit, you should run the average of them or the midpoint. The 70mph max and 40mph min on the interstates here mean a midpoint of 55, which I have done on I70 many times. That is a very busy interstate but its easier going 55 than 70. I could care less what other drivers think, the min is 40 so I am 15 over that.

Just remember, ALL states have a law about impeding the flow of traffic........

Just remember, ALL states have a law about impeding the flow of traffic........

First you got to have traffic to imped there none here in Idaho...

Seriously drive with common sense... Don't be a jerk about getting out of the way. If there is a pasing lane stay to the right and allow traffic to pass. If you have to slow down to allow the traffic to pass you.

Fuel distance for 35 Gallons

27 MPG = 945 Miles

26 MPG = 910 Miles

25 MPG = 875 Miles

24 MPG = 840 Miles

23 MPG = 805 Miles

22 MPG = 770 Miles

21 MPG = 735 Miles

20 MPG = 700 Miles

19 MPG = 665 Miles

18 MPG = 630 Miles

17 MPG = 595 Miles

16 MPG = 560 Miles

15 MPG = 525 Miles

14 MPG = 490 Miles

13 MPG = 455 Miles

12 MPG = 420 Miles

11 MPG = 385 Miles

10 MPG = 350 Miles

9 MPG = 315 Miles

Dark green is my typical economy driving. Light green is following speed limit. Red is trailer towing (7K to 8K).

I had a spreadsheet that I made to plug in the fuel price and MPG for certain speeds. Its amazing the saving that can be had, especially when towing.

Just remember, ALL states have a law about impeding the flow of traffic........

If enough "laws" are passed, everyone will be "guilty" of something 24/7. If you're not speeding, you're impeding. They got you coming and going now!!!

Here is what Mike doesn't show. If you look at his stuff, you see that everything is linear. So you would think 1mpg difference doesn't matter too much. In other words, he shows that going from 9 to 10mpg is the same increase in range as going from 26 to 27. Now lets look at it from a different standpoint, cost.

Now you can see that it is exponential. Going from 20mpg to 25.7mpg yields the same cost difference as going from 9 to 10mpg. This is why I am trying to get my truck as efficient as possible while pulling our trailer. Just think of how much Caj would save if he gained 1mpg.

My 4.10 geared truck is basically stock. Running empty in OD, I can get the best mpg (into the 19s) loafing on a 2 lane local Route at 45-50... only using the throttle when necessary. Highway driving in OD, I don't want to run 65 as the mpg will fall off... I see better mpgs at 55 but it's hard to keep it at that. I usually run 45-50 on secondary routes, 60-65 on the interstate (60 unless I need to drive faster) I'm not so much in love with driving fast anymore (retired/disability).

I can't stand driving slow. 65 in a 65 is about the best I can do, I'm usually 65 in 55s and 70-73 in 65s. My truck gets loud over 73 or so, that helps me slow down. A little. I'm just not wired for it....

The best mileage I've EVER gotten is 19.5, still with the NV4500, unloaded at a constant 55. Back to back with a 19.0 tank doing the same. I hate my 4.10s.

Around town, and most of the time towing, I'm around 12. Truck's ownership-long average is 11.8. Some fuel leak issues here and there have brought the average down. I also do very very little highway nontowing, but I was in the mid 16s doing 65 empty back and forth to MN right after the RTOO swap. I'd never done the trip with the NV4500 empty so I don't know how much that extra OD gives me.

RPM wise it's like putting 3.55s in, but there's a LOT more parasitic loss spinning the double countershaft trans internals I'm certain.

Someday maybe 3.55s so I can lope around at 1300 RPM at 70. That'd be nice.

I don't have an apples to apples, but I still expect 55 vs 65 is at least a 15% economy gain. The frustration of slow isn't worth it to me 80% of the time, though

--- Update to the previous post...

One other thing I was going to mention - I'm making a conscious effort lately to take off more gently around town and shift sooner (1850-2000 is my goal, if I don't pay attention I wind it out to 2500). I'm seeing a difference in the gauge, I'm thinking this tank will be around 13 instead of 11, and it has some towing on it too.

I can't stand driving slow. 65 in a 65 is about the best I can do, I'm usually 65 in 55s and 70-73 in 65s. My truck gets loud over 73 or so, that helps me slow down. A little. I'm just not wired for it....

The best mileage I've EVER gotten is 19.5, still with the NV4500, unloaded at a constant 55. Back to back with a 19.0 tank doing the same. I hate my 4.10s.

Around town, and most of the time towing, I'm around 12. Truck's ownership-long average is 11.8. Some fuel leak issues here and there have brought the average down. I also do very very little highway nontowing, but I was in the mid 16s doing 65 empty back and forth to MN right after the RTOO swap. I'd never done the trip with the NV4500 empty so I don't know how much that extra OD gives me.

RPM wise it's like putting 3.55s in, but there's a LOT more parasitic loss spinning the double countershaft trans internals I'm certain.

Someday maybe 3.55s so I can lope around at 1300 RPM at 70. That'd be nice.

I don't have an apples to apples, but I still expect 55 vs 65 is at least a 15% economy gain. The frustration of slow isn't worth it to me 80% of the time, though

--- Update to the previous post...

One other thing I was going to mention - I'm making a conscious effort lately to take off more gently around town and shift sooner (1850-2000 is my goal, if I don't pay attention I wind it out to 2500). I'm seeing a difference in the gauge, I'm thinking this tank will be around 13 instead of 11, and it has some towing on it too.

It's nothing but a mind game. If you overcome your need for speed, then you can go slow and have a better time doing it. I used to drive like you, only it was more like 80-90 on the interstates and well 80-90 on the highways too. Constantly watching for cops, constantly watching for deer, constantly holding on for dear life. I passed people left and right because after all, it is a cummins But I wanted to test out my mileage, and that required going slow. So I cranked up the radio, leaned back in the seat, set the cruise, took my shoes off, just relaxed. At first, it sucked. Everyone likes the thrill of showing what a cummins can do. But eventually, I got used to it a little more, and after a tank or 2 of driving like that, I went back to my old habits and it absolutely sucked. I never realized how much more attentive I had to be to go even 70mph. I said hell with that and have been driving slow ever since. The good thing is that I started going slow before I ever got any tickets/violations/anything.

The other thing is that you don't gain hardly any time going fast, you waste money on fuel as well as the parts that are now wearing out faster.

To add what ISX said..............when your as homely as I am; you don't give a crap about what folks think of you. Let the stupid MOFO's give you the finger when they pass you........they're gonna be the first ones to _____ and moan about fuel prices!!!!!!:doh:I had to see my tax accountant yesterday. So I drove down to the P's on Sunday morning and spent some time with them save for my time at my accountant. Came back today. I made it a point to drive 55-60mph there and back..............62 miles one way..............not to mention the 28 miles it was from the P's to my accountants place!!!!!! I had some folks pissed at me on Sunday when I drove down to the P's.......not much traffic. Today coming back was totally different. I had 18wheelers riding my dupa up the tollway even in the far-right lane!!!!! Are folks really that "stupid" now as far as speed vs. mileage goes??!! At least here in "The Peoples Republik of Illinoiz", it would surely seem so!!!

Like you said everyone is in a hurry to go nowhere... I'm sure I've told this story before but I've had people pissed off at me and tell me so when I've stopped for fuel but when I ask the person how must fuel mileage he/she gets "Oh 12-15 MPG" you know the person get rather pissy when you tell them to slow down and enjoy 20-22 MPG. I've also got another follower that calls on a regulare basis and he was asing would he be able to make a 190-200 one way trip with 100 gallons of diesel? I told him I can get 700-750 miles out of 35 gallon of diesel only if you slow down and get off the interstate. He typically drives 75-80 MPH... :banghead:

yea i used to have trouble staying even just at the speed limit but now that im driving a considerable amount every single day its not so hard to just sit back and relax watching the traffic flow byeven tried out going 60mph behind a semi for quite awhilefueled up again and got my 16.5mpg one of the days i got a heavy foot on that tank but it still kept my mileage up by driving slowermy last two tanks showed 16.5mpg and thats the best ive ever calculatedfrom the sounds of it i really cant expect more than 19 with my 4.10 though