Engine oil guides
Five guides that cover everything the label on a bottle assumes you already know. Start with grades if you are buying oil today, or approvals if you are trying to work out whether a cheaper bottle is genuinely equivalent.
Two numbers and a letter decide whether your engine is protected on a January morning or starved at motorway temperature.
Two oils marked 5W-30 can be chemically very different. The approval codes are what tell you which one your engine was designed for.
Manufacturer intervals assume a driving pattern most cars never see. Here is how to adjust for the one you actually have.
The base oil sets the ceiling on what an oil can do. On a modern engine there is usually only one honest answer.
Most oil-related damage happens between services, not during them. Checking properly takes two minutes.