Does my tow bar weigh me down.
 

I´ve noticed in my fuel-ups, that my highway consumption is 1.3 litres/100km over the manufacturers oficial statistics. I have a tow bar fitted in my vehicle, which I always have on. Does having the tow bar on, increase fuel consumption? I mean, is it affecting the aerodynamics of the vehicle? I find it hard to believe, that a simple piece of metal

weighing no more than a couple of kilos, can have something to do with it. Can anyone please share some light in the matter, as my city consumption is better than average, by about 0.4 litres/100km, it´s just my highway tank that seems to be over the average. thanks in advance!!

It won't make any difference. Of course, if you actually tow anything, your aero will be hit bigtime.

Yeah, but if you follow Formula 1 racing, the Red Bull Team, made a big difference in bettering their lap times, by modifying their rear aerodynamics with something called a "diffusor" (in spanish, sorry I don´t know what it´s called in English) and that is where the tow bar would be on the car!! So, I reckon that might cause some air turbulence, in a critical part of the car.

Yes, aerodynamics play a part in fuel consumption and seemingly minor modifications can have meaningful impacts. This is increasingly true as speed goes up. Aerodynamic drag increases with the square of speed so a car going 100 kph will have significantly more mileage impact than the same car going 40 kph around town.

If I've done my math correctly you're seeing something on the order of a 17% decrease in mileage at highway speeds so that seems pretty high for the kind of aerodynamic impact that a tow bar should have. I used your 31.4 mpg, doubled that to come up with 100 kms, multipled 3.8 by 2 (liters per gallon) and came up with 7.6 and divided 1.3 by 7.6 to come up with 17%, I realize that this is your overall average mpg, not highway but it is something better than a wild a$$ guess. I'd try putting the tow bar in the trunk for a few highway tanks and see if that makes a difference. Is that an option for you or is your tow bar permenantly mounted?

I´m back home from a trip, and I won´t be doing much highway mileage. The tow bar is not permanently fixed, and is in the garage, together with the spare wheel. As your mathematics is very good, I won´t quote any misapprehension, and I will post on this thread, my next fuel-up without tow bar, to see if I can better my best tank of 6.2 l/100km or 38.2 MPG.

I really haven´t any idea, if the tow bar is solely to blame for the apparent 17% over consumption on highway driving, but if it is, I´ve been burning hard earned cash, for being bone lazy, for about 4 years, because I couldn´t be bothered to take off the tow bar when not in use, and if a puncture kit comes with a new vehicle, why carry a spare wheel anyway. I apreciate your time, I will take any advice into consideration.

When you say "towbar" do you mean just the hitch (with ball attached) that goes into the receiver, i.e the metal frame bolted to the vehicle chassis.

If so this is relatively light, but for a comparison I'd be putting it in your garage, not the trunk.

It is unrealistic to expect the same MPG figs as the manufacturer states, since they will be testing under optimal conditions in order to produce an impressive figure.

hi, werewasi down under, & the rest of the crew. I really meant the hitch (with ball attached) actually, and not the permanently mounted tow bar, that´s under the rear bumper. Not a very impressive fuel up, 8.2 litres/100km or 34.3 MPG (UK). My wife has been doing some use of my car around town, and I haven´t really picked up much speed, to see if the hitch had anything to do with my fuel economy.

Nevertherless, I feel now that if I keep my City mileage below 8.4 litres/ 100 km or above 33.6 MPG (imperial) the car will do me time.

In my now deceased VW polo I had a small leak in the oil filter which blew oil all under the car and all up the bumper and boot lid. It was absolutely covered so I'd say the tow bar would cause extra turbulance.

If the air was blowing under then up the back of the car it's safe to assume it'll blow right through where the tow bar is.

Its not the tow bar itself that is heavy its the mount located underneath the rear bumper, thoose can be really heavy depending on the car 20-35 kilos, and remember a weight reduction starts with yourself

Don't forget weight has the biggest impact on stop/start driving, where you have to accelerate that extra weight. It won't make a big difference to highway driving.


For highway driving, the biggest impact would be aerodynamics, it's possible the frame under the car interrupts the airflow in a bad way, or even pulls the back of the car down a fraction which alters the whole flow over the car.


Personally I'd be sceptical that it actually makes a difference at all, and your figures are normal for highway driving in that car. How do your figures compare to other cars of the same type?


The only real way to tell would be to remove the complete tow bar, frame as well and test and then replace and test again, but given the amount of variables that can impact these kinds of tests, I would think you won't get a reliable answer.


Oliver.