For Douglas Adams the answer to life, the universe and everything was 42.
Always trying to stand out from the crowd, Europe's car industry executives have a different answer to the eternal question: 140.
That's the average grams per kilometre of CO2 emissions that car firms must meet from their entire fleet within the EU by 2008. In Japan that target must be reached by 2009.
If your model range includes several gas-guzzling SUVs, that magic figure may prove a severe headache. You don't have to spend too long with a car industry engineer before the 140 figure crops up in conversation.
While the powerpoint presentations in the marketing departments are all about segmenting the market to squeeze another few per cent of market share, over at the technical presentations the key is to add more small engined cars to dilute the average, or else introduce more environmentally friendly technology to the current engine range: hence the popularity of petrol-electric hybrid with many of the engineers.
According to Mr Fujimura, chief engineer of the Civic hybrid project at Honda, and the man behind the hybrid version of the Honda Civic saloon, due here later this year: "To reach the goal of 140g/km, we will need to expand our number of hybrid versions in the coming years."
Despite claims by makers such as Honda and Ford that they have always advanced the hybrid model, the public standard bearer of the hybrid revolution has always been Toyota.
Dismissed as nothing more than a halfway house between petrol and hydrogen by many European marques, these same firms that derided the hybrid efforts are now rushing to introduce their own versions.
General Motors, BMW and DaimlerChrysler are all busy pushing forth development of hybrid engines to catch the current consumer wave for greener transport.
Yet there remain some question marks over hybrids' ability.
While remaining positive about the future of hybrid, Jonathan Browning, head of sales and marketing for General Motors Europe says that some questions have to be answered: "The problem with hybrids is that it's hard to make an economic case for hybrids in the US, and hard to make an economic or environmental case for them in Europe."
His comments refer to doubts over the profitability of fitting both petrol engines and then the electrics involved in hybrid technology to cars. Even Fujimura admits that up to now hybrid has not been a profitable enterprise for Honda.
Toyota respond by stating that while the first generation Prius was not a profit earner, the current one is more than paying for itself.
Then there is the question of fuel economy. A study by Consumer Reports, a US consumer body similar to Which?, concluded that Toyota's claimed fuel consumption figure of 65.7mpg (combined) was unrealistic. In real-world driving conditions, fuel consumption was closer to 40mpg.
These "real world" conditions refer to long motorway stretches where the electric motors play little part in powering the car.
These motors are more useful in busy traffic, and city or town conditions.
That's when their true benefit is to be found.
Mr Fujimura admits as much, saying that for certain European driving conditions, like a lot of autobahn driving in Germany, diesel is a better option and that is why Honda offers a choice to European motorists, with both petrol, diesel and now hybrid engines on offer.
"Motorists can choose the power unit that gives them the best fuel economy for their normal driving environment," he notes.
In the end, hybrid may not be the panacea for our addiction to fossil fuels, but it goes a long way to helping particularly urban motorists dramatically decrease their fuel consumption.
And it helps the engineers reach that magic figure of 140 g/km.