There are few industries more complex than the car rental industry. If you are to engage with it, you need to prepare - meet them at their level, look them in the eye, make them wonder what to make of your cocked eyebrow - bemusement? Indignation? Fury? At every chance you must maintain the facade of total, inscrutable mystery and you must always, always have an ace in the hole.

This might be going too far.

It begins with enigmatic paperwork. The smallprint that matters will be hidden in the microdot of the first ‘i’. Be sure to take a magnifying glass with you, occasionally angling the sun’s rays onto the paper until it starts to smoke. This will force the clerk to move the paper. He will be ill at ease with this tactic, more accustomed to a quick signature and a smile. Better still, he will not know how to react to you producing a digital SLR from your clown-sized pocket in the name of full documentation of existing damage on the vehicle. Take your time with this step. Preferably, take a full studio with you, flash umbrellas and high-end desktop computer. Photograph every inch of the automobile, shouting impenetrable jargon every three to four seconds - ‘small wingnut gash on the fifth entailed vertebrae leading to potential probability inclination of eleven point four seconds, ensure pointing west at all times’. Choose your moment carefully, then drop kick the passenger-side front door. Before the clerk has time to react, grab his shoulder and reassure him you are merely ‘testing for tolerances’ and remind him the paperwork has yet to be signed.
An established rental company notes within its terms and conditions, ‘A Return Change Fee of $15 will apply if you return 24 hours or more prior to your reserved return date and time.’ Remember this when you sign into the contract: you are obligated to use this car. Your mission from this point on, as you part ways with the clerk, should be the complete, total decimation of the interior workings of the vehicle. Anything that is not immediately visible is fair game. Chances are high that you will be given an underpowered hatchback with the torque of a pig and the acceleration of a paraplegic sloth. Use this to your advantage. Abuse the vehicle, plant the gas pedal, leave your footprint on the floor. Request a manual transmission for extra satisfaction. There are few things in life more fulfilling, more rounded an experience, than hitting 7,500 RPM in a 1-litre unleaded hatchback and knowing, just knowing, that you are not to blame.

The opposite approach should be adopted when considering the exterior of the automobile. Consider the paintwork on your rental vehicle as sacred ground. Any slight indication that the car may sustain damage of some kind should be met with full evasive action. You are not paying the base rate plus taxes plus fees plus surcharges plus mandatory coverages plus navigational systems plus child seats plus additional drivers plus mileage only to sustain more collateral damage on your rapidly thinning wallet.

Apparently this says hire car.

On this subject of mileage, beware of the phrase ‘unlimited’. Regard the odometer as your total enemy, a sneak capable of tactics that would appeal only to the lowest common denominator of petty thief. Strike the canny balance between observing the terms and conditions of your unlimited mileage while ensuring that you do not, under any circumstances, exceed any kind of fair usage policies or daily caps, of which there are likely to be several. If you fear you will not approach the mileage cap within your allotted time due to prior commitments, it is your duty as a consumer to cancel any other appointments in favour of brimming that cap. Run the beast into the ground if necessary.

Ensure you return the car on the dead sound stroke of the agreed time. Wear at least three watches and carry an atomic clock in the boot of the vehicle. This is a contingency for the clerk disputing your return time. Refer him to Einstein’s law of relatively and acknowledge that, while you understand that movement at high velocities constitutes a bending of spacetime and as a result a slowing of time relative to any stationary body that may be observing the target, it is highly likely the clerk drove to work too and this would negate any time differential. Before he has chance to recover unleash a slide projector and allow the clerk full access to your printed record of what the vehicle looked like before he signed it over to you. Force the keys into his hand as you speak. Be prepared: this is when the clerk will play his ace in the hole.
You must be ready to counter immediately. He will ask you if you have filled the tank fully before returning the car. He will refer you to the terms and conditions of the agreement which states:

If the renter does not choose the prepaid fuel option and does not return the vehicle with a full tank of gas, the renter will be required to pay a fuel charge to compensate ___ for the cost and service of refueling the vehicle. The fuel charge is based on the estimated number of gallons needed to refill the tank multiplied by the rate per gallon charge specified on the rental agreement. ___ may use different methods of estimating the number of gallons needed to refill the tank and these methods of estimation necessarily rely on human judgment. Most ___ locations estimate the number of gallons needed to refill the gas tank either (1) by reading the fuel gauge to estimate the approximate amount of fuel needed to refill the tank (for example, one-half tank) and multiplying that number by the manufacturer’s specified fuel tank capacity, or (2) if the renter did not purchase any fuel during the rental, by reading the odometer to determine the amount of miles driven during the rental and dividing that number by the vehicle’s estimated fuel efficiency (miles per gallon) based on the manufacturer’s fuel efficiency specifications.

This is not likely to be your hire car.

You will not have filled the tank. It is human nature to attempt to circumvent any consequences which at first seem avoidable. But you will watch the clerk smelling the air, like a white collar Wolverine he will know the vehicle has been coasting on fumes all the way back to the lot. Your conversation must take place thus:

‘Evaporation.’

‘I’m sorry sir, I don’t quite understand what you mean.’

‘The air is far too dry in here. I used to work in air.’

‘But sir-’

‘Please… don’t apologise [press the keys into his hand]… I understand.’

Walk slowly out of the building. The clerk will most likely pursue you, but do not pay heed. Begin to hum loudly and consider the sun. As the clerk follows your line of sight, scarper around the corner. Your ace in the hole.