I own a 2006 Toyota highlander with 30,000 miles on speedometer. I change oil every 5000 miles using mobil one, 5w/20 fully synthetic mixing in 1 quart of lucas oil. I plan to change to Castrol syntec fully synthetic 5w/30 without mixing in the lucas oil. Will I possibly encounter any oil consumption problems or any others or am I good to go ?
Is 5w/30 listed in the manual for your conditions? Other than that, no problems.
All you need is any oil the meets or exceeds the specifications in the Toyota owner’s manual. It will list the weight oil required and the [SE]number. I doubt if the Lucas oil is hurting anything, but it also is not likely helping anything. You don’t need anything better than that which is specified in the owner’s manual
Also you likely don’t need to change the oil that often. If you are driving under what the owner’s manual says is normal, and if they suggest longer oil changes (say 7,500 or 10,000) you are quite safe to follow those recommendations.
Very few cars have problems related to oil unless they fail to follow the instructions in the owner’s manual. If you look in the recycle yard, you will find that only a small percentage of cars today get there due to oil related problems and most of them suffered serious neglect from their owners. Modern oils in modern cars don’t need additional oil changes. In fact there have been a few test that indicate the changing more often may acturally cause more wear, although, my take on it is that it is not enough to cause any manful reduced life.
The days when cars needed more often oil changes are gone.