Safe drafting and impact on mpg

[Arragonis]

Drafting at a safe distance can give quite a big benefit because it allows you to go slower. If I go slow (say 60 in a 70) then I can fine people not noticing the speed difference and coming up really fast before a "last minute avoid" lane change. If I put myself behind something obviously big and slow then this doesn't happen.

I also use the "2 second rule" to avoid piling into the back of anything, but also being that little bit further back means you can see "round" the vehicle in front more which means you can see obstacles quite a way ahead.

[freebeard]

Originally Posted by doclees

Any closer and may as well be towed. Rocks, blown tires, eh. What, you want to live forever? Keeps your reflexes sharp.

Back in the 80s I was following a dump truck at approximately a legal interval, when I observed a rock about the size of my fist that was stuck in its rear dual tires dislodge and bounce off my hood directly in front of me. Fortunately it bounced sideways, and knocked the outside rear view mirror right off the car. So in a sense, I am already living forever.

[radioranger]

the best way I found to gauge distance is watch as the debris , leaves etc, get carried along in the trucks wake, if your there your good, can be a pretty fair distance, also someone mentioned buffeting another good indicator , roll down your window and when you feel the air popping in and out of the car ,I think your drafting . either way you've got to stay glued to his brake lights for reference, and if he should crash, you do too. most likely. probably works better on a pickup than anything, I've actually felt gains when someone tailgates me with the right shaped car, can't remember what kind but it happens.

[CigaR007]

Here is a video of a tuft testing I did a few months ago. Notice at 3:10 how the airflow is somewhat attached (center of rear glass) and becomes very turbulent and detached when I stop drafting the bus in front of me.

http://www.youtube.com/watch?v=TpFLbOzxWn0

[nbleak21]

Originally Posted by doclees

Tankers are best.

I've found this to be true in my car, while in my truck, the trailers that have those "Kamm wings?" On them netted the best FE

[Fat Charlie]

Safe following distances change depending on speed, weather, time of day, traffic, etc. I wouldn't get closer to something just because I'm drafting it, in fact I'll generally give it at least as much distance as I would a car because a good truck is hard to see through. If it's big enough to be worth drafting, it's punching a big enough hole in the air that you can do it from a safe distance. Besides, P&G won't let you pick an exact distance anyway.

The worse your car's aero, the more drafting will help. I find that I can get an mpg boost if the rig is going at my speed, and I can hang on to one going around 10 mph more than I want to go without hurting that trip's numbers- but I've found that trying to catch up with one isn't worth it.

I draft a lot less than I used to, but I think that's because I'm pickier about drafting opportunities than I was.

[a8ksh4]

I agree about the heavy traffic "drafting". Some of my best mpg has been from 25-45MPH speed-up then slow-down traffic on the freeway.