Should I keep my sinking funds in one account or separate accounts for each goal?

You can do either, and the right choice is about clarity, not returns. Keeping each sinking fund in its own nicknamed sub-account, one for car maintenance, one for holidays, one for travel, makes progress toward each goal visible and prevents you from accidentally spending vacation money on a car repair. Many online banks let you open multiple sub-accounts free with the same high yield, so separation costs nothing. The alternative is one combined savings account where you track each goal's share in a spreadsheet, which means fewer accounts but requires discipline to avoid double-counting. Whichever you choose, keep all sinking funds distinct from your true emergency fund so planned spending never gets confused with genuine emergencies. Most people find separate labeled buckets far easier to stay motivated with.