I believe I have the same problem also. I changed oil using Mobil 1 High Mileage 5-30, the big K&N filter and Lubro Moly Engine Flush, about 650 miles ago. It was completely full to the top mark, but now it is almost to the bottom mark. My daughter who owned the vehicle before me, complained about this also. There doesn’t seem to be any evidence of burning or leaking oil.

The RX runs great. This past week I changed the spark plugs and PCV valve and cleaned the throttle body. The old plugs looked good and the puff of white smoke that occurred when first started is barely noticeable now. The old PCV valve (screw in type) had sludge on the bottom and the throttle body was very dirty especially on the IACV side. Idles great now.

I believe I have a sludge problem. I was thinking about topping off the oil with Marvel Mystery Oil to help with any sludge. I have used MMO in the past and it seemed to work great. It is less expensive than Auto-RX. I know it has only been 650 miles, but the oil on the dipstick is still almost clear and doesn’t seem to be getting dirty.

 

holy cow ... hypervish - the link is awesome.
they are having the exact same problem I seem to be having.
I have the '02 - like aejaz.
so the question is should I get the valve cover replaced or just monitor and top off oil as needed ?

jolomo - check the front valve cover to confirm if you have sludge, I though I had it - but turns out I dont.

 

I'd use Auto-RX if I were you. I'm not a big fan of additives but Auto-RX has been proven to work.

Also, I'd stop using the Mobil 1. There are numerous threads on here of people experiencing oil consumption with Mobil 1, including myself. (keep in mind though that there is people that still use Mobil 1 and have no issues)After switching to PP I haven't consumed any oil.

 

If I were in your situation, I would replace the valve cover. It seems to be the issue here, but of course no one can guarantee that. If the consumption wasn't so bad I'd be inclined to just top off as needed.

 

What is PP? Does it have sludge removal additives and lubricate as well?

 

Pennzoil Platinum. It's a full synthetic and can clean very well (tbn of 12) which is fairly high. You can also use Pennzoil Ultra, but I don't think it's worth the few extra dollars.

 

Add me to this list...my Lexus and Nissan drank Mobil 1. No consumption issues whatsoever with Pennzoil Platinum.

 

I am ready to change from Mobil 1. Changed the PCV and removed the valve cover. Only some varnish and very little soft sludge in some of the cavities. Looked like Lexus2k2 valve cover pictures. Oil still disappearing.

What weight of Pennzoil Platinum are you using?

 

I dont use it yet .. will swith it in next time.

hypervish reccoments PP 5W-30 .. and dont forget to check the link posted in earlier post:

https://www.clublexus.com/forums/rx-...lve-cover.html

 

You can buy a sludge remover that you run with your oil before you drain it. It works.

Nulon Oil System Cleaner (best product ever)
http://www.nulon.com.au/testimonials/fuel/

 

I switched to PP 5-30, replaced the PCV valve, checked for sludge under the front valve cover and oil pan. Some sludge in the oil pan. I replaced the plugs and the old ones had a nice light brown color, no signs of oil fouling. Also no signs of an oil leak or smoke coming out of the tail pipe.

I decided to take the 2001 Lexus RX300 on a trip. Traveling across Texas, I averaged 22 MPG, traveling 75 to 80 MPH. The RX ran great but every time I stopped for gas at 300 miles, I had to add a quart of oil.

I wish I knew what is going on!!!

 

Look into the link I posted a few posts above this. You may have a rear valve cover issue.

 

Check the breather hose in the PCV system. This is the one that goes from the airbox to the front valve cover. If this hose is plugged you will get excessive vacuum in the crankcase resulting in increased oil consumption.

 

Thanks Baetke for you input. My breather hose was completely clogged. Unfortunately, I did not discover it until today. I saw your post about 1500 miles into a 4500 mile trip we were taking. We just decided to complete the trip and add oil as we went along. The oil consumption diminished as we drove along the California coast at a much slower speed.

Unfortunately, as we headed home, the check engine light came on. We had 1000 miles to go and although the RX shook at low speeds, it was acceptable at 70mph. When we got home I noticed I forgot to replace the oil filler cap at the last gas and oil top off stop. I checked the oil and it had not gone down, which led me later to check the hose.

I have the P0302 code. My #2 plug was really oil fouled and I had only 60 psi of compression. I ran air through the cylinder at BDC and air was coming out the exhaust pipe. I guess an exhaust valve is leaking. Not sure what to do next.

 

What about other cylinders?

Salim