To draft or slow down?
 

I drive 130 miles round trip to work everyday, 2/3 is on the turnpike. I typically cruise at 75mph but I have dramatically changed my driving style this week. I have been cruising at around 62mph instead. I have noticed almost a 15% increase in economy. One thing that concerns me is that at this speed EVERYONE passes me, even tractor trailers. I am just waiting for one to not be paying attention.

Most trucks seem to cruise in the 67-72mph range. If I can find one that is around 65-67mph and draft behind it, do you think I will have the same amount of fuel economy?

While I know it's not safest thing to do, I believe that it IS safer (at least in my mind) for me to be behind a single truck instead multiple trucks coming up fast behind me.

Does anyone know for sure, or should I just test and find out?

I have a 99 civic hb auto, fyi.

Thanks!

I'm interested to see the response. I live in the DC metro area and have a similar issue when driving on the highway. P&D driving is a bit of a challenge because of this.

Part of the solution is probably aero modifications to reduce drag.

Before drafting a truck, look to see how the trailer is bouncing on the suspension, if it's jiggling about a lot, it's likely unloaded and deadheading... find a different truck... look for one with a slow periodicity on the suspension bouncing... that one is well loaded... it has 4x your stopping distance and will maintain a steady speed, and is less likely to be changing lanes all the time... but it will be slow to follow up grades. Try to follow at a distance that lets you see the brake lights on the tractor unit, underneath the truck... this means that should a line fall off on the trailer, you'll still see it's braking... you're also usually far enough back to catch signs of "shine" of the brakelights of the vehicle in front of it off the road surface.

RoadWarrior: So your suggestion is.....

I don't remember the exact numbers, but in my Odyssey, 70mph with a 3-second draft was slightly better than 65mph in the open.

PaleMelanesian: Are you consistently getting 60mpg? Tell me about your ride.

That's my civic, manual. My best highway drive was 75 mpg over 150 miles. High Speed Pulse & Glide in a 40-60 mph range, adjusting to the terrain. Near the crest of a hill, 40, in the bottom of the valley, 60. I have a grill block, and my tires are at 60 psi, and I use a Scangauge.

I've done the same drive using P&G behind a truck at 70mph, and got 55mpg.

Scangauge does what exactly?

I like seeing 60mpg without any really crazy modifications.

Scangauge tells you everything the car and engine are doing, at any moment. It also tells you instant and average gas mileage. Scangauge.com has all the details.

There's also an ongoing group buy at CleanMPG for cheaper. I'm over there more than here. Try reading the articles they have. It's all written down there. I just take all the ideas and run with them.

Heh, forgot that bit, I usually find that drafting uses much less fuel at any speed up to about 75mph... beyond that, you seem to be having to get too close for comfort at that speed, and seem to get thrown around more by wake vortices, meaning you have to keep stomping the gas to catch up again.

The trucks that are moving quick though are more likely to be the unloaded ones, which are difficult to follow, due to having shorter stopping distances, more likely to be changing lanes, and their trailers have a tendency to wander around a bit, dumping you out of the draft when they go from one side of the lane to the other. So generally finding one of the ones going steady in the right hand lane is better.

So drafting something big anywhere in the 60-70 range is great for F-E. Might seem to have progressively less effect the better aero your vehicle has, but weight seems to play a bit of a part, since, in my Escort Wagon, I seem to be able to gain 20mph from a truck without moving my foot, whereas in the minivan it's more like 5 or 10... this is when you pull out into draft... like from the entrance ramp or changing lanes.

My best mileage was following a trailer about 125 feet behind at 65-67. The trucks are slowing down for the same reason you are.

304 miles on 4.627 gallons of gas, most of it on I64 and 95 just south of DC.

I dont have a scanguage, my car is a 94 VX with just over 30k actual miles, on the original tires.

regards
gary

To throw a third option into the mix, will P&G work better than either of these? Can anyone post links to the articles on CleanMPG?

I'd love to have the gearing in your VX. Mine's running over 3,000 rpm at 65mph. Racertim, your automatic has longer gearing than mine, too, so you can use steady-state cruise up to a higher point than I can, as well. If I'm going more than 50mph, I use P&G the whole time.

Just go to CleanMPG.com and click the Articles link on the side. Here's the main one, though: https://www.cleanmpg.com/forums/showthread.php?t=1510

These days I drive pretty much 55 mph on the highway where 65 mph is alowed and sure, everybody pases you but I don't think I have ever felt unsafe.

I have a computer on one of my cars that shows the instant mpg and drafting does save gas for sure, but at some point, when a truck goes too fast I am better of just doing 55 mph (which is a bit more relaxed than drafting as well which I find I can do only for so long at the time). I would say that if a truck does more than 62/63 I am gonna let it go and go back to my 55 mph as that seems to be the spot where drafting no longer saves me gas as opposed to going 55 mph.

What, really? I thought you had to be much closer to benefit from drafting. I think I can handle 3 seconds. I know that at non-highway speeds I'm quite comfortable at 3 seconds.

One thing to consider when drafting, especially when drafting big trucks: Road debris kicked up by tires will chip away at your paint and windshield. If something big enough to put a chip or crack in your windshield hits, you've just blown a year's worth of drafting savings...

@theholycow: yes, but think of all the excitement :)

Yes. There's a clear benefit out that far. Of course, you'll get amazing results 10ft off the back bumper, but that's just stupid. I read a study using 2 semi trucks, and at 10ft, the trailing truck got a 50% boost in mileage.

I recently drove across Nevada, Utah and Wyoming on I-80. A lot of this driving was right after dawn, on a weekend, and the road was very, very deserted. I was doing about 55. A few times I did something very unorthodox: I moved to the left lane to let a truck pass me on the right.

I did this only under circumstances that I almost never encounter in my normal driving: there was no one else around, and I could see from literally a mile away that he was approaching me, so there was plenty of time and space for both parties to understand what was going on.

I kept a constant speed, and I moved way over to the left edge of the left lane, to make it easier for them to understand my intentions. I moved to the left when they were about 1/4 mile behind me.

They appreciated it.

"Road debris kicked up by tires will chip away at your paint and windshield."

Good point. I've had windshield damage that way. It's one reason I'm reluctant to get into drafting.

More than road debris, I'd worry more about those chunks of rubber ( known as gators in circles I don't travel in) that come off the tires; or worse yet,as a result of a blow out. That might do a lot more than crack your windshield.
I do draft at times,but on a long stretch of highway, I like to P&G behind the truck. The fast traffic will most likely see the truck at a greater distance and get into the other lane before getting close to you.

I guess that depends on the road you are traveling. I am on a 3 lane interstate which has zero congestion. While traveling at 62mpg for an entire week, 130 miles round trip, I passed ONE vehicle. It was a beat up Oldsmobile that I don't think was capable of 60mph.

Many times I see trucks coming up behind me at around 70-72mph and when there is a car in the middle lane, I see them get very close to me and have to use their brakes. I know they don't like this and it sure makes me nervous every time I see this in my mirror.

I just feel much safer when I am in control and I am doing the passing. That's one reason this style of driving is difficult for me. However, after putting gas in my car today, it was hard to argue with a 23% increase in fuel economy. I spend about $350 a month on gas right now, this is going to save me about $80 a month.

I have reduced my speed to about 57 to 59 mph. I stay in the right hand lane, here in California every one does 75 to 80 in all lanes. I really have to be aware of fast cars in the slow lane. This includes trucks. If there is an open spot to my left i will move over and speed up just enough to let the car or truck pass then back to the slow lane. Here in the L.A. area are a lot of container haulers. On the Long Beach Freeway they form long lines and draft. Its almost impossible to get to the slow lane from the fast lane to exit. When i find one by itself i draft because they usually only go 55 to 60 and every one is passing them.

This reminds me of a rant I have: Around here, if you're going slow in one lane (say, for example, the right lane) and there's nobody in the other lane, and a car comes up behind you going faster, they'll get right up close and then brake hard and tailgate forever. Why are people afraid to change lanes?

Anyway, forcing those trucks to brake, besides being scary, wastes a lot more of their fuel than it saves of yours, if you're concerned about that sort of thing.

Those people waste fuel always; if not you it will be the next car they catch up to. They are just to lazy to change lanes and think by scaring you, you'll go faster; and perhaps expect to draft you,but at their higher speed.I would not concern myself with their mileage.

Law of the universe: "People are stupid."

Anyways, when people do that to me, I simply slow down to the speed limit. If that doesn't work, I slow down even more. I do it gradually, rather than brake-checking. Usually pisses 'em off enough to pass.

About 2 years ago I drove from Richmond to Detroit and back, forgot the miles but it was more than a short drive... The worst of it was, the speed limit really is 65 MAX and everyone and I mean EVERYBODY does at LEAST 70!!!

Now I'm in an older bmw and this presents yet another unique challenge:
If you have ever driven a sporty car you know this, if you pick up your speed at ALL the entire rest of the Interstate gets into 'racing' with you... Yes very funny, THIS would be one of the reasons why sports car drivers do the speed limit.

But the absolute worst is the tailgating...
Here I am in the slow lane minding my own business, cruise and all going, there's nothing in the fast lane and nothing coming... But sure enough every single fool coming up from behind glues themselves to my bumper and stays there.

They won't switch lanes, instead they RIDE me...
What a PITA...

And so...
That is how I learned a highly interesting technique, which involves a fair to considerable amount of concentration, and that is to drive backwards through traffic... It works somewhat just like when you're in a real rush you weave in and out to get through, except now you study your rear views and you purposefully (but easily vs. rushed) switch lanes!

You switch lanes to LET those Nascar wannabees pass you.

Yup, just like that.
And it does work best with 18-wheelers, most of them 'get' what you're doing and
actually appreciate it. For one it's a pain to switch lanes in a big rig.
With car drivers you get a few funny looks, but oh well.

The interstates here are very congested and in many cases if you follow at a reasonable distance you begin to feel like a dormat, with cars pulling over in front of you less than a couple of car lengths apart.

95 North from Richmond to DC is almost always very congested, unless you want to drive at 3 AM. On a Sunday morning trip with few big rigs (relatively speaking) I got 50 MPG compared to 65+ with the major difference being I was drafting a big rig, with enough distance to stop between my VX and the trailer. I was carying an additional 300 pounds (almost 800 total) on the 50 MPG run, probably would have done 55 with the same weight as the 65+ run.

My VX is a time capsule, just passed 30 k original miles. The only thing I have done other than totally stock is to reverse the intake snorkel so it draws air from the top radiator hose.

regards
gary

The EPA hydraulic hybrid document states the aero drag at 65-70 is 70% of total energy cost. If you can eliminate any significant portion of that drag percentage it translates into mpg. This is offset somewhat by the fact that the smaller amount of total energy required results in slightly lower engine efficiency.

A good comparison is a bicycle with a total wind blocker bicycles can approach 70 MPH with a capable cyclist, while 35 is about the max with no wind block.

Slowing down works to a point, but I wouldn't dream of driving that stretch of 95 at 55, 10 below the limit. You would be risking your life if you dreamed of doing that on that particular stretch of road.

It was amazing on the 65+ mpg run to watch the fuel guage not moving.

passing on the right
 

I'm surprised to read here that some people purposely get in the left lane to let others pass. I do that occasionally but it depends on the road. If it's 2+ lanes and not an area with heavy traffic or frequent exits than I do that.
-andy

I agree with all the folks who moved to the left to let others pass, but do you worry at all lane violation tickets? In some places, it's illegal to pass on the right (serves the jerks right, but the professional truckers OTOH don't need that); and in some places, it's illegal to cruise in the left lane (exposing you to a ticket by a power-tripping cop).

I drive in reverse as well. My Jeep can't hit 75 MPH without a hefty push of the pedal.

No sucker tickets for me and I have been doing this for about two years.

I do enjoy drafting. I can get 4 car lengths behind a truck and notice a difference.

The aerodynamics of the sitch are usually that there's a "draft" out to 3 lengths of the vehicle making it, so a nice big semi with 20ft of rig followed by 55ft of trailer has draft out to 225ft at 65mph. However a typical van will only have draft out to about 50ft. So obviously the bigger the vehicle you follow, the further back from it you can be, and the safer it is.

I have moved over when the vehicle behind me got too close for comfort, especially if it has no effect on the overall traffic flow. This is rare around here. Generally my driving habits are constantly adjusted for the situation, with my basic premise being to have the least effect on other drivers unless they are totally inconsiderate. A good example is the space case tailgater, they dont know how to drive, just how to follow someone too closely to be safe, even on an empty road. They get the pulse and glide treatment.

regards
gary

dodging traffic in reverse doesn't make sense to me; maybe for a tractor-trailer when there are No Truck lanes to the left.One problem I see is that when you start to move over into the left lane to let them by, the tailgater suddenly decides to pass with foot to the floor and hit you anyway. A safe driver is one that drives in a predictable manner. Going the speed limit or less in the right lane is what most people expect. The tailgater has two choices; slow down or pass. If neither of these is good enough,too bad.I'm sure everyone has heard complaints about slow drivers in the "fast lane".This works both ways.

"dodging traffic in reverse doesn't make sense to me"

I only did it (let trucks pass me on the right) because of the very unusual circumstances (miles of visibility, no one else around). Normally I wouldn't do it.

And when cars came along (on the same road, in the same circumstance), I made them pass me on the left. It just seemed to make sense to do it this way (that I would move over for trucks but not for cars), for fairly obvious reasons.

If I'm on a road with only one lane in each direction, sometimes I'll move over to the shoulder to let someone pass me.

Ok, please understand driving in reverse is rare for me as well. I only do it to avoid accelerating to 75MPH in my Jeep.

It doesn't make sense because the rude, tailgating drivers are likely "smarter" where you live. Your average speeder may know to stay in the left lane and fly by traffic. I live in Louisiana and drive through places like Vinton, LA; Vidor, TX and Beaumont, TX to get to Houston, TX. The "I rule the road" mentality is as strong as the moonshine sold at the local drive thrus down here. ;)

I think I am going to declare drafting as the winner here. It seems a lot of people have the same problem of other people driving like idiots. Also, it seems as if there is more MPG to be had by smart drafting than slowing down.

Thanks for all the help thus far everyone, please keep your opinions on drafting vs slowing down coming.

Huh?
 

What's the benefit of this to you? What's the benefit of this to the truck driver?:confused:

This happens to me quite regularly these days, but I don't care about it at all. I don't care if the other driver (i.e. truck driver or Joe Schmo) is "inconvenienced" by me abiding by the rules of the road. I don't care if they are less fuel-efficient and/or it adds 12 more seconds to their trip time by having to slow down and go around me. It's their problem, not mine. Perhaps they'll eventually learn to plan ahead and improve their driving skills.:)

:thumbup: :D

I thought that only happened here in GA
 

Yeah, I don't understand this at all! I assume that they're not really paying attention to their speed and they just accelerate until something gets in their way and then they just follow it. It's like they're just mindlessly driving. Scary.:eek: But they don't really bother me too much. I just ignore them for the most part.:thumbup:

Not scary. They're "professional" drivers. Most have been very well-trained to avoid accidents. As a group, even with their extra mass, they're considerably more apt and able to avoid accidents than the average non-commercial driver. They have much more to lose (e.g. job, very expensive rig, trailer, and cargo) by causing, or simply being involved in, an accident than the average non-commercial driver.:cool:

A pain? Really? How?:confused:

Yeah, I support ticket-writing for left-lane (or the 2 "inside" lanes on 4-8 lane interstates) losers who cruise along at the same flow (+/-2 MPH) as the traffic in the adjacent lane. Although I can say that I've never noticed anyone being stopped for that violation. I guess the cops, in some areas, are just very selective in which laws they choose to enforce.:(