Rx300: Synthetic Vs. Regular Oil

[Hadyourphil]

I recently acquired an '01 with 161,000 miles to replace my recently deceased '01 with 250,000 miles. I have a gallon or so of synthetic oil left over from the previous RX and I am wondering whether I can use it for my next oil change. I don't think this car has ever had synthetic oil in it and at this mileage, straight synthetic might not be the best idea. Could I use it if I mix it 50-50 with regular oil?

[lenore]

Its not going to hurt anything, But maybe pick up high mileage synthetic and mix 50/50 with that for two oil changes.

[eugene.s]

the structure of synthetic and mineral oil is different - you use either of these but don't mix the two

[Hadyourphil]

That certainly doesn't explain the many kinds of regular and synthetic blends out there...

[eugene.s]

Hadyourphil, you are right. Am not an expert in oil and cannot give you an informed view on the details you are seeking for. But if you google for it, I am sure you'll find a lot.

From all my experience, the simple rules for oil are never to mix different types of oil (in this case, mineral/synthetic/semisymthetic) and even not mix the old and the new same type of oil (=no "adding" instead of replacing, only a full replace, even with some extra capacity for washing out the old oil as fully as possible) and even further, withing the same type of oil, dont mix different brands. These come as very basic advice I always got from all the mechanics (with no exception) in my life.

But if there are oil experts in here (which is simply a too narrow subject and I doub't there are any), I'd certain look for their expert/scientifically justified advice...

To stress, I never heard that any oil mixing might have a neutral effect

[lenore]

My thoughts are buy Castrol Oil 0-30 weight European formula oil. It will not only clean the engine well, but even at high mileage work very well. I switched to this at 110k miles on my old RX300 and it not only cleaned, but the engine was smoother, and I had no oil use issues. It is a true class IV synthetic and is very well liked on the Club Lexus site for this vehicle. Autozone carries it, but I am sure it is available elsewhere.