Honda R18 engine recommended oil viscosity is 5w-30. use any fully synthetic 5w-30 engine oil. do not use 10-40 in R18 engine.
If there is delay in shifting, most likely gear oil needs changing.
also never run R18 engine without thermostat valve. i hope your car fans are not direct and are working as per the temperature requirement.
also get the tappets adjusted. which city r u in? i might be able to suggest the right mechanic to you.