Everything we have measured.
29 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 2
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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.
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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 2
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Home EV chargers: they all stop at 11.5 kW, so buy the cord
Four of eight home chargers publish an output range and all four top out at 11.5 kW. The figure that separates them is cord length, which runs 16 to 25 feet.
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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
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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.
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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
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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.
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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.
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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 4
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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.
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Jump starters: peak amps is not the number that starts your car
Peak amps last 20 to 50 milliseconds; cold cranking amps is sustained for 30. The two units advertising the highest peak publish no CCA at all.
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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.
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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
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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.
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OBD-II scanners: price buys almost no extra data
Across a 22× price range the number of live data channels barely moves — the correlation is +0.16, and the unit reading the most costs $50.
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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
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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%.
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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.
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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.
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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.
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The shop says your brakes are at 4. Four what?
A pad measurement is millimetres of friction material, and 3 mm of every pad is unusable — so half the thickness is about a third of the life.
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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.
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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.
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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.
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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
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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.
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Dilution ratio calculator — 1:10, 1:20, 1:128 into any bottle
How much concentrate goes into a 16, 22, 24 or 32 oz bottle at any ratio. Shows both readings, because brands do not agree on what 1:10 means.
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How long will your tyre actually take to inflate?
Published inflator times are measured on one tyre. Enter your tyre size and get the time each measured inflator would take, arithmetic shown.
The gap 1
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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.