How to design a test drive route
The standard test drive — a right, a right, a right and a right, ten minutes, back to the lot — is designed to be pleasant. A useful one is designed to make specific faults reveal themselves, and it needs about half an hour and four kinds of road. Here is the route, leg by leg.
Two things before the route. First, plan it on a map at home, before you go, so that you are not navigating and evaluating at the same time. Second — and this is the part that does most of the work — drive the same route on every car you look at. Almost nothing on this page is judged absolutely. It is judged against the last car, and you cannot do that if every drive happened somewhere different.
The conditions
- Radio off. Windows down for the first half. You are listening, and a car's sounds reflect off the buildings you pass.
- Ask the seller not to narrate. Politely, once, at the start. Conversation is how ten minutes pass without you noticing anything.
- The engine starts cold, and you have already watched it do that — see the cold start. The drive is step two, not step one.
- Bring a phone note and stop twice to write in it. Impressions from leg two do not survive leg five.
Full lock, both directions, forward and back
Before you go anywhere, use the empty lot. At full steering lock and walking speed, the driveline and steering are under the most awkward loading they ever see, and several expensive things announce themselves here and nowhere else.
What this leg tests
- CV joints — tight circles both ways, windows down
- Power steering — for effort that varies as the wheel turns
- Transmission engagement into drive and reverse
- Low-speed brake noise, with the windows open
- Parking brake, on a slope if the lot has one
What a bad one does
- A rhythmic clicking that speeds up with the wheels — a CV joint
- A groan at lock, or a heavy spot mid-rotation
- A delay of a second or more before reverse engages, or a thump when it does
- Grinding that is present at 5 mph and gone at 30
The worst-maintained road you can find
Every town has one. Frost heaves, patched trenches, a railroad crossing. This is the suspension and body-structure leg, and it is the reason to keep the windows down and the radio off.
What this leg tests
- Struts and shocks — the car should settle in one motion
- Bushings, links and mounts
- Interior trim and how well the car is screwed together
- Whether anything in the trunk sloshes
What a bad one does
- Clunks over single bumps — usually links or bushings, cheap to find, annoying to ignore
- Continued float after a dip, two or three oscillations
- A rattle from the dash that was not there on smooth road
- Steering that tugs at your hands over ruts
Traffic lights, on purpose
Find the arterial with a light every block and catch all of them. Most of a car's life is this, and most transmission and drivability faults live in the first three gears and the first quarter of the throttle.
What this leg tests
- Low-gear shift quality, both directions
- Throttle response from a standstill
- Brake feel at ordinary pressures
- Idle quality in gear, stopped, with the air conditioning on
What a bad one does
- A flare — engine speed rising between gears without the car accelerating
- A shift you feel as a shove rather than a change
- A shudder at light throttle around 30–45 mph
- Shaking at a light that smooths out in neutral
- Air conditioning that cycles on and off every few seconds
Load, heat and engine braking
New Jersey has plenty of usable grade if you look — a long bridge approach counts. Climb it at a steady speed, then come back down without riding the brakes the whole way.
What this leg tests
- The engine under sustained load
- The transmission's willingness to pick a gear and stay in it
- The cooling system, watched on the gauge
- On the way down: engine braking and brake heat
What a bad one does
- Hunting — shifting up and down repeatedly on a steady climb
- A temperature needle that climbs and does not come back
- Loss of power that arrives after a minute rather than immediately
- A hot, sharp smell at the bottom of the descent — see the smell test
Full-throttle merge, then cruise
Use the on-ramp properly — a real merge is the only legitimate excuse to open the throttle all the way, and it is where a tired engine or a slipping transmission stops hiding. Then settle at highway speed and hold it for several miles, which is longer than it sounds and is the point.
What this leg tests
- Full-load acceleration and upper-gear shifts
- Vibration at speed — wheels, tires, driveline
- Straight-line tracking with a light grip
- Wind noise and door seals
- Cruise control, which nobody remembers to try
What a bad one does
- Engine speed climbing without the car doing the same
- A vibration that appears in a narrow speed band and then clears
- A wheel-speed shimmy through the steering wheel
- Whistling from a door seal — often a sign a door has been off
The braking test, done safely
An empty, flat, dry road with nobody behind you. Check the mirror, warn your passenger, then brake firmly — not an emergency stop, but harder than you would ever brake by accident — from about forty. Do it once.
What this leg tests
- Whether the car stops straight
- Pedal feel under real pressure
- Rotor condition, felt rather than measured
- With light fingers on the wheel for two seconds: alignment pull
What a bad one does
- Pulls to one side — a caliper or a hose, not the pads
- Pulses through the pedal — thickness variation in a rotor
- A pedal that goes further than expected and feels soft
- Drifts steadily one way on a flat, crowned-road-corrected straight
Park it, get out, and leave it running
The most useful minute of the drive happens after it. The car is at full operating temperature for the first time today, which is a state it was not in when you arrived.
What this leg tests
- Leaks that only appear hot and pressurized
- Cooling fans — they should run and then stop
- Smells that the engine bay was too cold to produce earlier
- The hot restart: shut it off, wait a minute, start it again
What a bad one does
- Drips on fresh pavement where there were none this morning
- A fan that never runs, or one that never stops
- Long cranking on a hot restart when the cold start was fine
- Sweet steam at the front, which is coolant and ends the visit
Then go somewhere else
A test drive is not an inspection. Everything above is what a car will tell you from the driver's seat, and there is a whole second category of finding that only exists with the wheels off the ground — what a lift shows you covers it. If the drive goes well, that is the next appointment, not the last one.
Our version of this
Take the car. Take it for half an hour, take it on the highway, take it past your own mechanic if he is open. We are not going to ride along narrating, and we are not going to hand you a pre-planned loop that happens to avoid the bad pavement on Route 9. Six cars at a time means we already know what each one does on every leg above, because somebody here drove it that way before it went on the row — and it is all written on the inspection sheet in the window.
Drive within the speed limit and within conditions; the hard stop described in leg six should only be attempted on a clear, dry road with no traffic behind you. This is general guidance for evaluating a vehicle, not a substitute for a pre-purchase inspection by a qualified technician.