There will be two of us traveling to London in September. Do I need to purchase two separate Oyster cards or can I pass it back for my partner to use?

I will only be in London for 4-5 days. Is this the best transportation option?

You each need your own card.

We were in London for 4 days in September. We (5 of us) each bought our own card, loaded with I think 20 GBP each, plus the 3 GBP deposit. We used it often -- on all but one day, we hit the cap. Only one person had to add money to his, and that was because something got screwed up electronically (I'm sure he could have gotten it corrected if he had taken the time). When we were leaving Heathrow to come home, we turned them in and got the balance back, including the deposit.

Adding to my previous post, we figured out the daily cap (the cap is equal to what a 1-day TravelCard would cost) and added on for the Heathrow trips in order to figure out how much to load on the card initially (we bought they at the airport when we arrived). But it doesn't matter, because you can always add more, and get back the balance.

Your best transport option depends on your goals. Unless we're going all the way across town (such as to Greenwich), we prefer buses to the Tube for a number of reasons. The Oyster caps bus travel at £3 per day.

If you're there for 5 full days and will be using public transportation a lot, you may come out ahead by buying a 7-day travelcard loaded onto the Oyster. But if you're only there for 4 days and not using much public transport, then you can just use Oyster PAYG.

I think there's also a 3-day travelcard? It may or may not save you $ over the Oyster PAYG.

I believe the 7-day Travelcard for Zones 1-2 is 25.80, which does make it a good deal even for 5 days if you are going to travel a lot on public transportation. (At 25.80, it's only slightly more than 5 times the Oyster PAYG off-peak daily cap). If you won't hit the cap every day, then the PAYG Oyster is a better deal for 5 days, because you get a discount on each trip, and never pay MORE than the cap.