Hi all, i have to put some 10W40 in the car the other day on a long drive. Low oil came up on the screen so i had to stop and all the garage was the 10W40. i put 3 ltrs in. I just concerned that its bad for the engine, i usally use 5W30. My car does burn alot of oil so will i just wait till it needs a top up to go back to 5W30 or can i use the 2 ltrs i have left of the 10W40