It’s well known that following a large vehicle on the highway can improve a car’s fuel efficiency. This kind of tailgating is called “truck drafting”, as I understand it, and is often regarded as impolite, dangerous, etc.
My experience is that I can remain about 10 m / 30 feet behind a semi-trailer on the highway and and still get some benefit (as per my car’s instant fuel-mileage indicator). I know, I’m probably still outside the driver’s field of view, etc.
My question: Does the presence of my car in its wake have any influence on the truck’s fuel efficiency? I know it would be negligible in any case, but is there an influence or isn’t there?
On the one hand, the boost I’m getting must be coming from somewhere; on the other hand, it’s hard to imagine my car having an influence on a vehicle that’s 10 m ahead of it on the highway. Apart from gravitational attraction, I mean.
You have to be so close that you prevent the truck’s own turbulence from swirling down/around and back onto the back edge of the truck. You have to be a few feet away – maybe inches – to have the front of your car deflect and carrry turbulent currents that otherwise would pull/act on the rear trailing edge of the truck. If you were that close, the truck would be more aerodynamic and experience less drag.
How does the fuel savings compare to the cost of paying all those fines for tailgating and reckless driving? Don’t forget Child Endangerment if you have anyone under 18 with you in the car…
As mentioned, drafting can actually increase the fuel efficiency of the lead vehicle. It’s all a question of the aerodynamics of the entire system. If the shape of your vehicle at the back of the truck reduces turbulent losses that might otherwise be occurring, it’s helping.
As proof of principle, consider the Space Shuttle tail cone, pictured here. The tail cone could be thought of as a tiny vehicle that has pulled up behind the shuttle/747 combo, improving the fuel efficiency of the shuttle/747 combo.
Mythbusters did an experiment on this and found even 50’ back would improve your mileage some, in fact when they were inches away the trailing car did a lot worse due to not being able to stay that close without constant adjustments.
Gruntled, we don’t really need this kind of thread-crapping in GQ. The OP has already acknowledged it may be dangerous. If you have an opinion about this you simply must state, take it to the Pit.
According to Nascar racing, specifically at high speed tracks like Talladega and Daytona, even the leading car benefits when multiple cars are following each other closely. It has something to do with reduced drag behind the leading car.
I do not know if if translates to trucks and cars at normal road speed.
There’s no reason why it wouldn’t. In fact you could chain up an unlimited number of vehicles and they would all be more efficient. The difference may not be very significant for the lead vehicle though.
The fuel savings doesn’t need to “come from” anywhere - it’s not a zero sum game. The more aerodynamic a vehicle (or chain of vehicles) is, the more efficient it will be.
Funny if it should turn out that I’m improving the truck’s fuel economy, although I have no intention of following close enough for that. In my original question, I was expecting that my wake-surfing would actually cost the truck some fuel.
