Everything we have measured.

32 findings, each one a figure somebody independent published and we reprinted with its conditions attached. This list is built from the pages themselves rather than typed out, so it cannot fall behind them.

Tyres 3

Tyre tread depth: the legal minimum is a floor, not a target

An EU-commissioned report puts the increase at 30 to 65 per cent at the 1.6 mm limit, and says the curve turns below 3.5 mm. The law is a floor, not a target.
Performance summer tyres: seven metres between best and worst

Eight tyres, one size, one car. The wet braking spread is 6.94 m — at the point the best has stopped, the worst is still doing 38 km/h.
The all-season tyre won nothing — and lost in the rain

One car, three tyre types, three surfaces. Summer won dry and wet, winter won snow, and the all-season came last in the wet, behind the winter tyre.

EV charging 3

EV winter range: the cold takes an eighth, the heater takes the rest

AAA measured both. At 20 °F with the heater off an EV lost 12 per cent of its range. With the heater on, 41. Only one of those is a choice you make.
Home EV chargers: buy the cord, not the output figure

All eight home chargers publish an output ceiling and five stop at the same 11.5 kW. What separates them is cord length, which runs 16 to 25 feet.
32A vs 40A vs 48A: the home charging amperage you can actually use

A 48-amp charger needs a 60-amp breaker, and your car may cap the rate anyway. Work out what your panel and your car will really give you.

Dash cams 2

Dash cam parking mode: buffered recording and hardwiring

Parking mode is the most advertised dash cam feature and the least measured. What the buffer does, why a 12V socket will not run it, and what six claim.
How far can a dash cam actually read a plate at night?

Nine dash cams, one number plate, measured in feet by day and night. The best managed 30 ft after dark; a 4K camera failed where a 1440p one succeeded.

Detailing 3

Car vacuums: two labs measured suction in two different units

Car and Driver prints suction in inches of water, MotorTrend in kilopascals, and neither converts. Ten vacuums, put on one scale.
Pressure washers for cars: the psi figure is not a measurement

Every pressure washer is sold on a psi number the maker supplies. The one test that put a gauge on the line read 1000 psi through a car-washing nozzle.
The best dual-action polisher for a beginner, by weight and noise

Which DA polisher to buy first, decided on the two things anyone has measured: how heavy it is and how loud it is, every figure sourced.

Accessories 5

Ice scrapers and snow brushes: what the tests measured was reach

Car and Driver measured six ice scrapers and snow brushes: reach runs 25.0 to 59.0 in, blades 3.8 to 4.5. Neither it nor Road & Track timed a clearing.
An empty roof rack cost a sedan 11 per cent of its fuel economy

Measured at 65 mph: an empty roof rack cost a sedan 11 per cent of its fuel economy and an SUV about 2. A hitch carrier returned 25 mpg against a box's 21.
Jump starters: peak amps is not the number that starts your car

On a 2026 load tester the pick, rated 800 A cranking, held about 360–480 A at 7.5–9.5 V for several seconds. Peak amps is the opening jolt, not this.
MagSafe car mounts: hold strength promised, never published

The highest-ranking test of magnetic car mounts is written by a mount manufacturer and contains no hold-strength figure in any unit.
Tyre inflators: the fastest is 4.3× the slowest, on the same tyre

Six inflators timed from 10 psi on one 245/50R20 tyre. The spread is a factor of four, and the usual time-to-30-psi figure flatters the small pumps.

Repair tools 3

Jack stands: the recall that no spec sheet could have predicted

More than 1.7 million jack stands were recalled after being found able to collapse under load. The cause was production tooling wearing out.
OBD-II scanners: price buys almost no extra data

Across a 19× price range the dearest scanner reads 20 live channels and the cheapest 16. What price buys is the ability to command the car.
Torque wrenches: your big one is out of spec on a spark plug

A click wrench is certified to ±4 per cent, and only over the upper part of its scale. A 1/2 in drive wrench is out of specification below 40 N·m.

Problems 9

Brake pad thickness chart: what 4 mm really leaves you

Pads start at 10–12 mm and the last 3 mm can never be used, so a 4 mm reading leaves about 11–14% of the life. The chart, millimetre by millimetre.
Cloudy headlights give you a fifth of the light

Measured to FMVSS-108: eleven-year-old lenses put out 22% of a new headlight, and only original-equipment replacement measured back at 100%.
Old brake fluid boils lower than cheap new brake fluid

Federal law sets a boiling point for every DOT grade, dry and after moisture. Fresh DOT 3 outperforms wet DOT 4 by 50 °C.
Old wipers leave half the windshield smeared

Measured in one pass: worn blades cleared 53.1% of the glass, new ones 89 to 95.1%. Replacing them matters far more than which brand you buy.
The octane number is the wrong number to look at

AAA measured no gain in horsepower, economy or emissions from premium in cars designed for regular. The figure that mattered is not on the pump.
Turning the fan up makes your cabin filter worse

Peer-reviewed measurement of what you breathe in a car: efficiency falls as fan speed rises, and cheap aftermarket filters cut nitrogen dioxide by nothing.
Your battery died in July. You found out in January.

Batteries last 58 months in the far north and under 41 in the far south — heat does the damage, cold only reveals it.
Car won't start and clicks: what the clicking actually tells you

Rapid clicking and a single click mean different things. The measurement that settles it is voltage while cranking, not voltage at rest.
Tyre pressure light on a cold morning: it is not just the cold

Cold costs about 1 psi per 10 °F. The warning lamp is required to light at 25 per cent below placard — about 9 psi.

Tools 3

How many oil changes is the 3,000-mile habit costing you?

The 3,000-mile interval is a habit, not a specification, and California's own waste agency says so. Put your manual's number in and see the difference.
Dilution ratio calculator — 1:10, 1:20, 1:128, 1:200 into any bottle

How much concentrate goes into a 16, 22, 24 or 32 oz bottle at any ratio from 1:4 to 1:256. Shows both readings, because brands read 1:10 two ways.
Tyre inflation time calculator: how long each pump takes

Six portable inflators took 1:34 to 6:40 to bring one 245/50R20 tyre from 10 to 30 psi. Enter your size and pressures to scale each time to yours.

The gap 1

The gap in your own gear is bigger than the gap between brands

Across the categories measured here, the gap between a worn part and a fresh one is larger than the gap between the brands you could replace it with.

Pages that carry no measurement of their own are not listed: the disclosure, the privacy and terms pages, and the method, which describes how a number gets onto a page rather than reporting one. The three calculators are here because each one scales a published measurement to your case.