Transportation and Vehicle Ownership · Chapter 4
Maintenance, warning signs and tire safety
The owner's manual tells you what this vehicle needs. Use general knowledge to know what to check. Use the manual to know what your vehicle requires.
The vehicle-specific authority
The owner's manual is the starting point
NHTSA repeatedly directs vehicle owners to their owner's manual for tire pressure, coolant specification, child-restraint installation, safety-technology operation, and vehicle-specific maintenance recommendations. The manual is not a suggestion. It is the manufacturer's instruction for how to maintain, operate, and care for the specific vehicle you own.
If the manual is missing from the glove box, check the manufacturer's website for a digital version. Many manufacturers offer downloadable PDFs by year, make, and model. Knowing where the manual is and being able to find information in it quickly is a practical skill that pays off every time a dashboard light appears, a maintenance question comes up, or someone needs to install a child seat.
Owner's manual scavenger hunt
Find these in your manual before you need them under pressure:
Recommended tire pressure
Maintenance schedule for your driving conditions
Correct oil specification (if applicable)
Coolant type and capacity
Dashboard warning light explanations
Spare tire and jack instructions
Child-restraint anchor locations
Driver-assistance system descriptions
Build a maintenance schedule from the manual
The manufacturer's maintenance schedule lists service items and intervals specific to your vehicle. These may include engine oil and filter, cabin and engine air filters, coolant, brake fluid, transmission service, spark plugs, belts, tire rotation, brake inspection, battery testing, and hybrid or EV-specific inspections. Do not substitute generic internet advice for manufacturer instructions. A universal "change oil every 3,000 miles" or "flush transmission at 30,000 miles" may be too often for one vehicle and not often enough for another. Vehicle requirements differ. Use yours.
What you can check
Owner-level inspection
NHTSA's seasonal driving guidance recommends that vehicle owners pay attention to tires, coolant level, fluid levels, battery and charging system, lights, wipers, belts and hoses, floor mats, and recall status. These checks do not require professional tools. They require walking around the vehicle, opening the hood, and comparing what you see against what the manual describes as normal.
Owner-level tasks the manual commonly permits include checking and adjusting tire pressure, adding windshield washer fluid, replacing wiper blades, checking fluid levels using marked dipsticks or reservoirs, checking lights, and inspecting belts and hoses for visible wear. The manual also tells you what not to touch. If the manual does not describe a check as an owner task, it probably requires professional service.
Fluid leaks require attention
NHTSA advises having the vehicle serviced if fluid leakage is observed. The types of fluids and systems vary by vehicle. Do not attempt to identify every leak by taste or skin contact. If you see a puddle forming under the vehicle that was not there before, or if a fluid level drops noticeably between checks, schedule a professional evaluation.
Dashboard warnings are vehicle-specific
Dashboard warning lights vary by manufacturer and model. The owner's manual is the place to learn what each light means for your vehicle. In general, lights divide into three categories: information indicators that tell you something is on or active, caution warnings that indicate a condition worth monitoring, and urgent warnings that require immediate attention. The specific meaning of each symbol is in the manual, not in a generic chart from the internet. If a warning light activates and you are unsure what it means, pull over safely and check the manual before continuing.
Safety boundary
Know when the vehicle should not be driven
The most important maintenance skill is not knowing how to fix something. It is recognizing when continuing to drive can turn a repair problem into a safety problem. You do not need to diagnose the cause. You need to recognize the condition.
Conditions where driving may be unsafe
Brake failure or a major brake-system warning
Severe steering difficulty or loss of steering control
Engine overheating with a dashboard warning
Tire sidewall bulge, blowout, or major tire damage
Flat tire
Severe or sudden fluid loss
Smoke or fire from the vehicle
Fuel leak or strong fuel odor
A manufacturer "Do Not Drive" recall instruction
Unsafe wheel or tire condition
Any condition where the owner's manual instructs you to stop
If any of these conditions occurs, the correct response is to stop driving safely, protect the occupants, and arrange for professional evaluation or towing. "The car still moves" is not the same as "the car is safe to drive." This section teaches vehicle checks, not vehicle repair. The boundary between them is the line between what the manual describes as owner maintenance and what requires a trained technician with proper tools and safety equipment.
Road contact
Tire safety is not optional
Tires are the only parts of the vehicle that touch the road. Everything else, braking, steering, acceleration, stability, depends on four patches of rubber no larger than your hand. Keeping them properly inflated, undamaged, and adequately treaded is one of the simplest and most consequential maintenance habits a vehicle owner can build.
Check pressure monthly, cold
NHTSA says tire pressure should be checked at least once a month when tires are cold, meaning the vehicle has not been driven for at least about three hours. Include the spare tire when the vehicle is equipped with one. Use a quality tire-pressure gauge, not your eyes. Tires can be significantly underinflated without looking noticeably flat.
Use the vehicle placard, not the tire sidewall
NHTSA states that the correct vehicle inflation pressure is found on the Tire and Loading Information Label, typically located on the driver-side door area, or in the owner's manual. The maximum pressure number molded on the tire sidewall is the tire's maximum rated pressure. It is not the vehicle manufacturer's recommended operating pressure. Inflating to the sidewall number can produce a harsh ride, uneven wear, and reduced traction. This is one of the most common tire-pressure misconceptions.
TPMS is not a substitute
NHTSA says tire-pressure monitoring systems warn when a tire is significantly underinflated. They do not warn at the first sign of pressure loss, they do not monitor tread condition, and they do not replace monthly manual checks. Treat TPMS as an alarm system, not a maintenance program.
Inspect condition and tread
NHTSA recommends inspecting tires at least monthly and before long trips for cuts, punctures, bulges, scrapes, cracks, bumps, and uneven wear. Any significant damage should be evaluated by a tire professional rather than ignored.
NHTSA's current guidance identifies 2/32 inch as the minimum tread-depth replacement threshold. The penny test (insert a penny head-first into a tread groove; if you can see the top of Lincoln's head, the tread is at or below 2/32 inch) is a basic consumer method NHTSA describes for identifying this threshold. Important context: 2/32 inch is a minimum, not a performance guarantee. Wet-weather and snow traction can deteriorate well before the tread reaches that depth. Replacing tires before they reach the legal minimum is often the safer choice, especially in climates with frequent rain or snow.
Tire age matters
NHTSA notes that some tire and vehicle manufacturers recommend tire replacement at a particular age, sometimes around six years, regardless of remaining tread. Rubber degrades with time and exposure even when tread looks adequate. Check the tire manufacturer's guidance and the vehicle manual for age-related replacement recommendations. Do not assume a tire is safe solely because it has tread left.
Rotation, replacement, and matching
NHTSA states that rotation, balancing, and alignment can help tire life and performance. Follow the vehicle manual, tire manufacturer, and service professional for intervals and patterns. When replacing tires, match the size, load capability, speed rating, and type the vehicle manufacturer specifies. Do not select a replacement tire solely by price. A tire that does not match the vehicle's requirements may affect handling, braking, and safety.
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Sources
Where this guidance comes from
- NHTSA, Summer Driving Tips, accessed 2026-08-11.
- NHTSA, Winter Driving Tips, accessed 2026-08-11.
- NHTSA, TireWise / Tire Safety, accessed 2026-08-11.