Is it smarter to split my emergency fund into a starter tier and a full tier?

Tiering can make the goal feel achievable and keep your money working harder. A common structure is a small, instantly accessible cushion of one to two thousand dollars in checking or a linked high-yield savings account for same-day surprises, then the bulk of the fund in a high-yield savings or money market account you can reach within a day or two, and optionally a third slice in short-term Treasuries or I-bonds for the portion you are least likely to touch soon. The point is matching liquidity to how fast you would realistically need the cash. Keep enough truly instant so a car repair does not force you to sell anything, but let the rarely-touched portion earn a bit more. Do not over-engineer it; two tiers is plenty for most people.