Lexus using oil

Messages
1
Location
Coffeyville,KS 67337
I recently bought my friends Lexus SC400,nice car, in excellant condition. It has 85,000 miles on it. He had used Castrol GTX, since it was new. I used Auto-RX as directed with the Castrol. I then changed to Mobil 1 S.S. 10-30. The problem is it now uses about a quart every 1000 miles were as with the Castrol it was using about 1/2 a quart between oil changes, every 3,000 miles. Any ideas? Switch back to the Castrol or use another syn?
 
Messages
403
Location
California
Check for leaks to find out if that's where the extra 1/2 quart is going. Also how sure are you it was only using 1/2 before?
 
Messages
154
Location
Chicago
One of the factors may be that the Mobil 1 10-30 is a lower viscosity than the Castrol 10-30 9.81cst - Mobil 1 10.93cst - Castrol GTX (see various virgin oil samples on this forum)
 
Messages
378
Location
West Coast
It is a common phenomenon for a motor to consume newly installed synthetic oil after a long run with conventional. The syn oil, with its high solvency, is dissolving accumulated sludge and gunk left over from the conventional oil. For some reason, when this happens, more oil slips through the rings and is combusted. You should notice after a few thousand miles that your oil consumption will return to normal or better than when you where running conventional. This happened to my Volvo S70 when I switched from Castrol Syntec to Amsoil at 35,000 miles. This also happened to my Jeep Grand Cherokee when I switched from Chevron Supreme to Amsoil at 70,000 miles. In both vehicles oil consumption went up steeply after the initial change, and within about 5-6 k miles, things leveled off to a near zero consumption level.
 
Messages
47,649
Location
Duvall WA - Pacific NW USA
Typically there can be a temporary increase in consumption when switching to synthetic motor oil. My 245Ti did the same thing. Consumption went up, then locked down to essentially zero oil used after "awhile" (honestly don't remember) Why does this happen? I have heard some "non-scientific" explanations such as "cleansing" and "entrapping dirt and varnish" that are combusted. How long will it last? Depends on how much grub is in the engine. But the question I have, is why did it happen if you used AutoRx? What does the engine look like inside...? MOLECULE, ET AL - Why?
 
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