Regular unleaded is fine. It's a 4stroke so you don't need to add oil.
A Honda CRF-50 uses a 10w30 four stroke motorcycle oil. You should not use a truck or car oil in the CRF-50.
10w-40
Honda recommends 92 octane at least for this bike.
10w30 four stroke motorcycle oil. do not use car or truck oil!
5wt oil. Use Honda oil.
API SM oil is the kind of oil that a Honda CRF150f should use. Make sure the SM oil is either 10W-40 or 10W-30.
about a liter
10w40 oil if you are using a non-honda oil. We just switched our crf's (2 of them) to Amsoil and I can honestly say we felt a difference in the first 5 minutes!
87 octane regular
always use four stroke motorcycle oil. valvoline, castrol, Honda etc. I use 10 w 40. 20 w 50 is a little too thick unless your motor is worn out. NEVER use oil for cars and trucks.
i got a 2003 model i gave it an oil change and advised to use 10w/40 synthetic.
10w30 is a good choice year round. I highly recommend you use synthetic oil in this air cooled engine.