Choose a sleeping bag liner for the room you need, its feel against your skin and how you will wash it during the trip. A liner can keep sweat and dirt off the sleeping bag and add warmth, but do not count on a fixed temperature increase.
Try the liner inside your sleeping bag
For two nights by Lake Siljan, I would try the whole combination at home. Get inside. Turn over. Check whether the liner pulls across your knees or moves with you as you lie on your side.
A roomy sleeping bag will not make a narrow liner wider. Compare the liner's length, shape and opening with your body and sleeping bag. A five-minute trial tells you more about freedom of movement than a photograph of an empty product.
Sea to Summit's selection guide distinguishes rectangular travel liners from models intended for sleeping bags. It also discusses stretch fabrics for people who find a liner restrictive. Check the finished model's measurements rather than relying on the material name.
Balance comfort and packed size
When camping from a car, soft fabric and convenient washing may matter more than the smallest stuff sack. If you will carry the liner all day, its weight and volume must fit alongside the other sleeping equipment. Lay out your bag, liner and mat before deciding what to take.
I would shortlist two suitable models and compare their actual weights and dimensions. There is no reason to buy another accessory if your sleeping setup works and the liner would remain unused.
Plan for the whole sleeping setup
Sea to Summit explains why its Reactor liners have no fixed added-temperature rating: the effect varies with the sleeping bag, mat and conditions. A liner does not give your bag a new guaranteed comfort temperature.
Choose a sleeping bag for the expected overnight temperature and a suitable mat. If you already feel cold in that combination, examine the whole setup before treating a liner as the answer. Try a night close to home where you can go indoors if it gets too cold.
Follow the care label
The liner also needs washing after use. Sea to Summit's care advice recommends avoiding fabric softener and prefers air drying; tumble-dryer heat can damage silk. Follow your own model's label for washing temperature and drying.
Pack the liner once it is dry. On a longer journey, I would wash it at a stop that leaves time for drying, rather than seal it away damp before the next night.
A photo from that tent evening by Siljan can be saved with the overnight stay in FARON. Keeping the place and picture together on the map makes that particular weekend easier to find again. Log your first overnight stay.
Frequently asked questions about sleeping bag liners
Does everyone need a liner?
No. Choose one if you want a separate washable layer or prefer its feel against your skin.
How much warmer will my sleeping bag be?
No fixed value applies to every combination. Your bag, mat and conditions affect the result.
Will a rectangular liner fit a mummy sleeping bag?
That depends on the dimensions. Try them together to check that loose fabric stays comfortable and your legs have enough room.
Can a liner replace a sleeping bag?
Do not count on that for a Swedish camping night. Choose sleeping equipment for the temperature and the model's intended use.
