Hello I just recently purchased a Lexus RX 300 1999 AWD with 250xxx mile on it and I don't know when the last oil change was done and the engine has alot of sludge build up I wanted to know what product (seafoam,marvel mystery oil,bg...etc)would be best to safely remove the sludge without blocking up oil passage

 

Read this thread, Auto RX seems to be one good product. After that see if you can Find Castrol Oil 0-30 European formula oil. It has tremendous cleaning abilities.
https://www.clublexus.com/forums/rx-...k-auto-rx.html

 

Okay thanks for the info and where can you get the 0-30 oil

 

Some auto parts stores had it, but it was always difficult to find. I used it on my older RX300 and even the crust found under the oil filler cap was gone. The auto RX as I remember is a multi step thing. Pulling the front valve cover which is easy would tell you for sure if you have sludge. Maybe some others will tell you alternative oils that clean well. I know the moderator on this site used this oil in his RX300 for some time.

 

regular castrol gtx 5w30 is fine for cleaning , even conventional penzoil. 0w30 is overboard for cleaning purposes as it is a full synthetic. Though i haven't used auto rx, i've had good results with seafoam in the crankcase over several treatments.

Being the RX is a '99 with the earliest revision of the rear valve cover, the previous owners may have experienced the oil consumption issue and ran the car low on oil between changes..which can contribute to sludge. Knowing that the car is sludged, it has a high probability that the rear valve cover's baffles are completely sludged up. No amount of anti-sludging additive will cure it without removing the cover and soaking it. Consider a newer style rx330 rear valve cover if you experience oil consumption after attempting to fix the sludge.