A fuel economy run is a tricky business.

Over the past few years, fuel economy or fuel efficiency runs have become commonplace in the industry, particularly with automobile manufacturers, tire companies, fuel conglomerates and more. It makes perfect sense, as fuel economy is the number one factor (globally-speaking) to consider about a new car according to one Alan Mulally. You may have heard of him.

Personally, we've taken part in numerous eco runs. We drove the Ford Fiesta back in 2011 (Manila to Currimao), to the more serious ones like the Bridgestone Ecopia Eco Run (Manila to various areas in Pampanga), to the extreme runs like the Ford Focus TDCI Coast2Coast run (Sorsogon to Pagudpud) and the Petron Xtra Mile Challenge Media Edition (Pagudpud to Sorsogon).

There is a problem though: doing a fuel efficiency run or economy experiment tends to generate some really high numbers... digits high enough to raise eyebrows and suspicion.

Think 1402.4 kilometers on one full tank of gas aboard a 2008 1.3L Honda Jazz, 1,432.5 kilometers from a full tank of diesel in a 2010 2.0L Ford Focus TDCI, or 27.8 kilometers for every liter of gasoline in a drive across Metro Manila on a 2013 Mazda CX-5 2.5L. We once set a 50+ kilometer per liter figure driving a 2012 Toyota Vios 1.3J.

Are those numbers even realistic? More importantly, are those numbers really possible?

Personally speaking, I would advise that you take the results of a fuel economy run with a grain of salt; three grains, to be exact.

The first is the driving condition. We've driven on days when the sun was beating down hard on the road. We've driven in the wee hours of the morning (2AM to around 6AM) to have the clearest roads possible. We've driven through a late storm that had had branches, trees, a loose tire and even a part of a roof fly across our path. We've even driven with a security escort -either on two wheels or four- to open a clear path in crowded towns and cities and even to override the traffic lights.

The second thing to keep in mind is that a fuel eco run is (more often than not) a competition rather than a realistic demonstration. And being a competition with prizes or pride on the line, competitive drivers or teams tend to pull out all the stops on strategy and tactics to get the best mileage possible. We had lead or sweeper cars to take on unneeded weight like the rear seats, spare tires, tools and the like, all while the tires had higher-than-normal pressures. We even emptied the water tanks of the windshield washers. Some even fold their side mirrors, supposedly for aerodynamic efficiency; go figure.

The last thing about fuel eco runs is the driving style, as determined by how competitive or “career” you want to be.

We couldn't go fast; 60-70 km/h is typically the sweet spot, while some even underspeed on the expressway (i.e. 50 km/h). We shift vigorously to try to get to the lowest speed in the lowest RPM at the highest gear as quickly as possible. We drafted big rigs or buses ahead. We weaved to avoid everything instead of braking, all to maintain the ever precious commodity of momentum. Coasting in neutral was the norm. We took 'outside' lines on turns to increase the mileage, especially on downhill roads. Airconditioners were off. Windows were only slightly opened. On really long runs (i.e. 4 days) we smelled ripe towards the end and couldn't stand the sight or voice of each other anymore.

Such are the norms of fuel economy runs, and such are the reasons behind how these runs generate exceedingly high economy figures. If you could bend or break the rules and do things that no sane driver would do (i.e. pushing a car through a toll gate) without getting caught, you would; the degree only varied with what prize awaited the winners. Normal everyday driving has been tossed out the window and is being run over by the slow big rig that's flashing its lights at you for going so slow.

Things are changing though. Gradually, more and more manufacturers are trying to maintain a strict set of rules to follow to make the results more realistic and prevent such silly and downright dangerous acts from surfacing during a run. But much like the boundary system for bus drivers, so long as there's a prize or pride involved with fuel economy runs, road safety, sanity and dignity will always find a way to be sacrificed on the all-important altar of fuel economy.

Now you know what the asterisk is for.