Is it ok to top up with 10w-40 with 5w-30 in engine?

Topping up with 10W-40 oil when your engine calls for 5W-30 is generally acceptable in small amounts, as both are multi-viscosity oils and share similar properties. However, it's best to use the recommended oil viscosity for optimal performance and fuel efficiency. Mixing oils can alter the oil's overall viscosity and performance characteristics, so it's advisable to eventually use the recommended oil type for a full oil change. Always check your vehicle’s owner manual for specific recommendations.