best highway ecodrive tip?

[modmonster]

but i saw a picture of the stream lines on a truck somewhere on this site and the low pressure didn't extend that far back. you have to drive right behind the truck to see gains = unsafe.

is driving 4 car lengths back from a truck gonna save you anything or is it just the lower speed that saves you?

[99metro]

4 car lengths is still too close. At 65mph, you should be three to four of HIS lengths behind him, or about 200 feet, at the closest. Do the math so that you are no closer than 2 seconds behind him. I would love to find a truck going 50-55 mph so I could get two or three of his lengths behind him (2 seconds). If he drives any faster, I'm better off doing P&G.

[superchow]

I usually find it safer driving behind semi trucks. They can see further down the road and change their speed with greater consideration for efficiency, i.e. slower acceleration and braking. Also, if the truck decides to do an emergency braking maneuver, unless it is very light, should be far greater than that of a light (and well maintained) passenger car.

I have also achieved great mileage following a speeding vehicle (not too closely of course) because I presume their wake becomes larger at higher speed. However, when that person slams on their brake, their car's/truck's/SUV's braking distance is much shorter, and as a result I feel less safe following them.

The trick for me is to look down the road much further and anticipate traffic flows before they even happen. For example: ever noticed how during a traffic jam the traffic always speeds up right after an off-ramp? It's obvious "herd" behavior. "Oh - more space! I'll floor the accelerator to prevent the person beside me to merge into my empty lane!" Then everybody reaches the on-ramp of that exit and there's mass braking because the traffic bunches up again. Just that observation saved me from a few accidents already.

Of course, it helps if you're actually watching the traffic instead of planning your evening...

Drafting comes naturally to me now, and I use my wife as a "safety gauge". She tenses up when it's unsafe - for her. Four cra lengths has always been a pretty good distance to me, but I get closer when the truck driver seems to be driving attentively.

[modmonster]

do you ever get that feeling your being watched by the truck driver? they often weave side to side so they can see you in their mirrors when 5 car lengths back. is there a rule of courtesy between truck drivers where they take turns to draft each other. i've often wondered if they think me only drafting from them is selfish?

[superchow]

Originally Posted by modmonster

do you ever get that feeling your being watched by the truck driver? they often weave side to side so they can see you in their mirrors when 5 car lengths back. is there a rule of courtesy between truck drivers where they take turns to draft each other. i've often wondered if they think me only drafting from them is selfish?

Of course, but from their perspective, if I keep a respectful distance then I am actually helping their aerodynamic shape too. I had everything from a truck driver varying his speed by 15 mph to discourage me from drafting to blinker flashing as a "thank you". There are plenty of truckers that waved back at my wife (in the passenger seat) when we passed them eventually. (No cutaneous over-exposition was involved, mind you!)

This close to made my day: Courtesy on the highway! Ever blocked traffic behind you to give a trucker some room to merge?

If we all drove as if one's mother or Jesus or loved one, etc. was in every other vehicle, then accidents would turn into the exception. Imagine it is YOUR child playing on the street when you speed past it going 50 in a 25. (OK, rant over now...)

[Axaday]

I've made two out of town highway trips since getting the scanguage. I thought pulse and glide between 65 and 55 would be really good and that's what I did the first time. It got me great mileage.

But a month later I decided to try regular old cruise control set on 55 to see how much better the P&G was. The cruise at 55 was a couple MPG better and was, of course, much easier. Next time I'll try 50.

[Tourigjm]

I find P&G/DWL to be the most effective. I pulled down 49.54 MPG on a 341 mile trip on all hwy by doing just that. My average speed was about 52 mph (it was a long day) No Drafting (My car was full of stuff for school too, so it was significantly heavier.) I normally get around 40 MPG's with a mix of hwy/city driving.

[modmonster]

is drafting worth it or is driving slow better?

[Axaday]

Originally Posted by modmonster

is drafting worth it or is driving slow better?

I wouldn't presume to judge you, not knowing you, but I think more people think they are a good enough driver to do it than actually are. It is risky enough that I don't myself.

[PaleMelanesian]

Originally Posted by modmonster

is drafting worth it or is driving slow better?

I've tested it in my Civic and Odyssey. The results were similar. Drafting (3 seconds back) gave about the same benefit as driving ~6-7 mph slower.

I like to give myself enough space to stop if the truck was suddenly not moving at all. My car's stopping distance = my drafting distance. Let's say that's 150 feet. At 60mph, that's about 2 seconds back. Only time I'm closer than that is when they pull in front of me.

My highway advice:
Manual trans - P&G. 45-60 mph P&G is worth about 70 mpg in my civic in good weather
Automatic - DWL. 60 mph DWL in the Odyssey is worth about 29-30 mpg. (rated 18/25 old, 16/23 new)