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How to Keep an Oil Change Log
An oil change log is one row per fill: when, at which kilometers, what was done, what it cost, and when the next change is due.
An oil change log fails when the only record is a sticker you can no longer read. The row that lasts has a date, an odometer reading, the work (oil, filter, or both), the cost, and the next due mark.
The interval itself is a separate choice. How to choose an oil change interval starts from the owner's manual, not from a generic 10,000 km rule. This note is what you write after the oil is already in the engine.
RPMBase stores that row on the car you own, in the maintenance log, and can remind you from the mark you set. It does not decide the interval for you.
The fields an oil change log needs
Date of the change. Odometer on that day, copied from the invoice or the dashboard, not guessed a week later. Say whether the filter was replaced. If the invoice names an oil spec, copy that into the note. Cost, if you want the year to add up.
Next due is a date, a kilometer target, or both, taken from the interval you already trust. If the shop wrote one figure and the book says another, pick one and note why.
One visit is one row even if the invoice also includes a cabin filter or an inspection. Split the row only when those jobs need a different due date.
What not to put in the oil change row
Do not record a recommendation you declined as work that was done. A line that says the oil was suggested, and you waited, is not an oil change.
Do not invent kilometers to make the history look even. A blank odometer is more honest than a round number you made up in the car park.
Do not also file the same total in the expense log. The cost lives with the job. What car expenses to track keeps fuel and insurance out of this row, and keeps this row from being entered twice.
From the last change to the next reminder
The oil change due calculator can show a next kilometer from the last change and the interval you type. It is a one-off sum. It is not a saved history.
Save the row in the car maintenance tracker. The reminder hangs off that row, by date or by kilometers. A phone alarm that only says 'oil' will not tell you which car, or at which reading.
If you want a draft instead of an empty form, a sentence or a photo of the invoice can fill the fields. Nothing is saved until you confirm the date and the odometer.
Why the log matters next year
The next oil change, a second driver, and a buyer all ask the same thing: when was it done, and at which kilometers. A readable row answers that. It does not prove you used the right spec unless the note says so, and it does not raise a sale price by itself.
Keep the invoice. The log is the index. The paper is the proof. Routine jobs around the oil change sit on the maintenance schedule, not inside this one row.