Problems
Worked out, not guessed at.
Most people meet a car problem before they meet a product. Those searches are answered almost entirely by service chains, whose interest is an appointment, and by forum threads that contradict each other — and the answers are often wrong in the direction that costs you something. Diagnosis has real numbers behind it: legal thresholds, voltages, gas laws. We show the arithmetic and then say what to do.
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Headlights
A fifth of the light you paid for.
Eleven-year-old lenses measured 22% of a new headlight. Restoration triples that — and produces more glare than DOT criteria allow, which is not on the box.
22% of new
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Brake fluid
Old DOT 4 boils lower than new DOT 3.
Federal law sets a boiling point for every grade, fresh and after moisture. Absorbing water costs about a third of it — so fresh DOT 3 beats wet DOT 4 by 50 °C.
About a third, every grade
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Visibility
Worn wipers leave half the windshield smeared.
Measured in one pass: the worn set cleared 53.1% of the glass, new ones 89 to 95.1%. Replacing them is worth about six times more than choosing between them.
53.1% vs 95.1%
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Battery
It 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. Plus how to read the date sticker, where the letter I is skipped.
58 vs under 41 months
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Cabin air
Turning the fan up makes the filter worse.
Peer-reviewed measurement of what you breathe: efficiency falls as fan speed rises, and cheap aftermarket filters cut nitrogen dioxide by nothing while OEM carbon filters cut it 64–67%.
64–67% vs none
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Brakes
The shop says your brakes are at 4. Four what?
Millimetres of friction material — and 3 mm of every pad is unusable, so half the thickness is about a third of the life. At 4 mm you have 11 to 14 per cent left.
3 mm you can never use
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Won't start
It clicks. What the clicking tells you.
Rapid clicking and a single click mean different things — but a battery can rest at a healthy 12.6 V and still collapse below 9.6 V under the starter. Resting voltage does not diagnose it.
9.6 V under crank
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Tyre pressure
The light came on this morning. It is not just the cold.
Cold costs about 1 psi per 10 °F. The lamp is required by federal standard to light at 25 per cent below placard — about 9 psi. Temperature alone cannot do that.
~94 °F would be needed