The fuel system cleaning service offered at quick-lube facilities — typically involving a bottle of cleaner added to the fuel tank and occasionally a throttle body spray treatment — is among the more contentious upsells in automotive maintenance. The service is sometimes unnecessary, sometimes genuinely useful, and the recommendation is almost never based on an actual assessment of the specific vehicle’s condition. Understanding what fuel system deposits are, how they form, and what genuinely removes them separates useful maintenance from profitable theater.

Fourteen. That is the number of 1970 Plymouth Hemi ‘Cuda convertibles documented to have been produced with a four-speed manual transmission. The rarity of this specific configuration — the most desirable variant of the most desirable muscle car of the muscle car era’s final peak year — has made it the auction record holder for American muscle cars and the reference point against which all other American performance car values are indexed.

The engine air filter and the cabin air filter serve related but distinct purposes and are replaced on different schedules for different reasons. They are also subject to different sets of misinformation — the engine filter subject to aftermarket upgrade claims that are partially true and largely irrelevant for most drivers, the cabin filter subject to replacement intervals that many service facilities inflate well beyond what the filter’s actual condition warrants.

Car batteries fail for a small number of predictable reasons, most of which are accelerated by behaviors that are avoidable once understood. The lead-acid battery that sits in the engine bay of most conventional vehicles is a mature technology with well-documented failure modes and a service life that ranges from two years, in the worst conditions, to six or seven years with appropriate care. The difference is not accidental.

The primary enemy of battery longevity is deep discharge — allowing the battery to drain significantly below its nominal charge before recharging. Lead-acid batteries are not designed for repeated deep discharges. Each significant discharge-recharge cycle causes some sulfation of the lead plates — the buildup of lead sulfate crystals that reduce the plate area available for chemical reaction and permanently reduce the battery’s capacity. A battery that has been deeply discharged multiple times is a battery with reduced capacity that will struggle to start the engine in cold weather and will fail sooner than one that has been maintained at proper charge.

Car storage appears on its face to be passive — the car is not being driven, therefore nothing is happening to it, therefore nothing requires preparation or attention. This reasoning produces cars that emerge from storage with flat-spotted tires, discharged and sulfated batteries, gummed fuel systems, seized brake calipers, deteriorated rubber components, and pest damage to wiring and interior. The cars that emerge from extended storage in the same mechanical condition as when they went in are the cars whose owners understood that storage is an active process.

The cultural weight that a single film appearance in 1964 deposited on the Aston Martin DB5 has complicated its assessment as an automobile. The DB5 is a beautiful, capable, mechanically sophisticated grand tourer that would command serious collector attention based on its own merits. It is also the car that Sean Connery drove in Goldfinger, and that association has inflated its market value, attracted buyers who are purchasing cinematic mythology rather than automotive excellence, and made it difficult to discuss the car as an object rather than as an icon.

A car’s paint is under continuous assault from UV radiation, airborne contamination, bird droppings, road tar, tree sap, and the abrasion of washing that removes the compounds deposited by all of the above. The factory clear coat that protects the color layer is measured in microns and does not regenerate once it is removed. The paint protection decisions an owner makes in the first year of a car’s life determine the condition of the paint for the remainder of its ownership, and potentially through subsequent ownerships for cars that retain value over time.

Tires are the only point of contact between a vehicle and the road. Every input — braking, steering, acceleration — is transmitted through four contact patches, each approximately the size of a human hand. The condition of those patches determines the vehicle’s actual capability regardless of what the chassis, the brakes, or the electronics are capable of achieving. A car with excellent brakes and worn tires will stop in a longer distance than a car with mediocre brakes and excellent tires. Physics does not allow the alternative.

Wheel alignment — the orientation of the tires relative to each other and to the road surface — affects tire wear, fuel economy, handling stability, and steering feel simultaneously. A car with incorrect alignment is a car that is consuming tires unevenly, potentially using more fuel than necessary, and handling in ways that differ from its design intention without giving the driver an obvious indication that something is wrong. The deterioration is gradual enough that many drivers adapt to it without noticing until a tire is worn through on one edge or the car pulls strongly enough to require constant steering correction.

The Mustang Dark Horse represents Ford’s attempt to produce a track-focused Mustang that is analytically justifiable rather than simply powerful in the way that American performance cars have traditionally satisfied their performance requirements. The 500-horsepower 5.0-liter Coyote V8 is carried over from the Mach 1 with specific modifications — a new flat-plane crankshaft that allows the engine to rev faster and produce a different sound character — and surrounded by chassis, suspension, and aerodynamic development that is serious enough to require explanation rather than simply impressive horsepower figures.