A radiator cap is the pressure valve that seals your engine’s cooling system and holds it at a set pressure, usually 13 to 16 PSI. That pressure raises the boiling point of the coolant, and the cap also holds a vacuum on cooldown so the system stays full and free of air. When pressure climbs … Read more
To top off coolant correctly, park the car on level ground, let the engine cool completely, then pour BMW-approved coolant of the correct specification slowly through a clean funnel into the expansion tank until the level reaches the cold MAX mark. Never open the cap on a warm engine, and never fill past MAX. The … Read more
If your car sits for weeks at a time or only covers a few miles a week, change the oil every six months and never go past twelve, even if the odometer barely moved. Time ages engine oil faster than distance does, and the dashboard reminder will not warn you. Most of the wrong advice … Read more
Does high mileage oil work? Partly, and only for a narrow set of problems. It is an oil formulated for older engines, loaded with additives that soften aging rubber seals and add extra detergents. That can slow a weeping gasket or cut the oil an engine burns between changes. It cannot replace a worn part. … Read more
A motor oil bottle tells you three separate things: how the oil flows cold and hot, which performance tests it passed, and whether a specific carmaker licensed it. If you know how to read oil bottle labels and certifications, you can match any jug to your owner’s manual in about a minute and stop guessing … Read more
Metal in engine oil means particles of the engine’s own internal components have broken off and are circulating in the lubricant. It is usually wear debris from bearings, cylinder walls, piston rings, camshafts or the valvetrain, and it is either normal break-in on a new engine or a sign of accelerating wear on a used … Read more
Engine oil sludge is a thick, gel-like buildup that forms when degraded oil mixes with dirt, moisture and unburned fuel until it turns to paste. To check for engine oil sludge in a BMW, pull the dipstick and read the film, look at the underside of the filler cap, and rub a drop of oil … Read more
If your car has no dipstick, the oil level is read electronically by an oil level sensor in the pan, and you check it on the instrument cluster or infotainment screen. Here is how to check oil on a car with no dipstick: warm the engine to operating temperature on level ground, leave it running … Read more
Brake dust comes off a driveway by dissolving the oily binder that glues it to the concrete, then rinsing the loosened iron particles up out of the pores. Scrubbing it dry does the opposite — the metal acts like sandpaper under the bristles and drives itself deeper into the slab — and that single habit … Read more
You can tell if brake fluid is contaminated by looking for five things: dark fluid with sediment in it, a cloudy or separated sample, a pedal that sinks or feels springy, longer stopping distances or fade under repeated stops, and rust or metal residue around the lines and calipers. None of those is proof on … Read more