owenstrawn

The last couple years I have been trying to pin down my oil consumption issues. I had a trip planned this weekend so I was careful to check before/during/after.

Back in Nov I put in a new K&N HP-1002 and 5 qts of Mobile One 5W-30.

After 2,400 miles of 0-60mpg driving the oil level was still between the buttons on the dipstick. This was the start of the trip.

After 500 miles at 70-75mph driving I had to add 3 qts to raise the level between the buttons.

After another 500 miles at 70-75 mph I had to add another 2 qts to raise the level between the buttons.

Also, my fuel mileage has dropped under 17 mpg at 75 mph, though I can still get 21+ mpg at 55mph.

This is a 2000 RX300 (AWD) with about 173k miles on it.

I'd appreciate any comments or suggestions on what might be the cause of these problems or whether they can be fixed.

Thanks!
Owen

2KHarrier

Well, it appears your's is suffering from the same fate as so many other RX's on here. Oil consumption due to a poorly designed PCV valve and oil baffle on the rear valve cover.
I would check to make sure the PCV valve is operating correctly, and look for signs of oil sludging in the engine. It's worth the time to pull the front valve cover to see what everything looks like after 180K miles. It's an easy one to remove.


Read through this info thoroughly...

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

If you can swap out the old valve cover for the newer designed cover yourself, it's roughly a 7 hour job...

hypervish

First thing I would do is try another oil, such as Pennzoil Platinum.

There was only one time that my RX consumed oil, and that was when i ran Mobil 1 prior to a road trip. Aside from that my RX has never consumed oil, and I've never tried to run Mobil 1 after that.

owenstrawn

Thanks! That thread is very helpful!

matts6887

I just picked up a used 99 rx 300 from a lexus dealer last week. I just hope I dont encounter any of these oil burning issues you guys have had because there is no way i can afford to pay someone to replace the cover, gaskets, etc, for me as i just dont have the funds available to do so. So with that in mind im keeping my fingers crossed as far as this goes as i cant afford to be without a vehicle either as I am always on the go; everyday. And the biggest thing too is as everyone knows; oil is like the lifeblood of any engine. Lose any and or all oil and its pretty much game over as eventually you will have nothing but a huge paperweight sitting around. And oh yea; mine has a bit over 131,000 on the clock so far. So am I biding time on this just waiting for it or do any/all of ya think I am ok for now?

2KHarrier

Well Matt, without doing some investigating, there's no way to speculate. Some easy things you can do:
Take a look at the rear valve cover area on the passenger side of the engine. Look at the style of PCV valve installed. If it appears to be pressed into a rubber grommet, it's the older style. If it's threaded into the VC, it's the newer style. I'm willing to bet it's the older style valve. Some guys on here have not changed the valve cover and PCV valve, and are not experiencing any issues, so it's not mandatory to replace the cover. It is imperative that the PCV valve is working correctly, however.
They're pretty easy to change and cheap to buy as well. That should be changed at least every other oil change.

It's all about getting familiar with your vehicle, especially important when on a tight budget.

matts6887

Very true 2kharrier; on the part its all about getting familiar with your vehicle. True that. What part is it exactly you are talking about that should be changed every other oil change and is that mandatory?

owenstrawn

matts, I would start by keeping track of the oil level over the course of the next couple of changes. If you don't have to add any between changes, then why worry?

I'll be checking/changing my PCV, then I'll watch to see if I still have a problem. No more problem will definitely mean no valve cover change for me.

Thanks for all the help!
Owen

2KHarrier

Matt;
Here's a thread all about PCV valves..


https://www.clublexus.com/forums/rx-...cv-device.html

Read thoroughly... Knowledge is power with a Lexus.....

2KHarrier

Yes, swapping out the PCV valve is a good practice. It keeps the ventilation system for the engine clean.

trhs75

One of my '99's had its highway oil usage problem completely solved by switching to Pennzoil Platinum oil. On the other '99,switching oil brands has not solved the problem. I've considered changing the valve cover to the newer style, but that doesn't sound like a lot of fun. I have noticed an oil leak under the right front of the car. It comes from higher up in the engine than the oil pan and I'm not sure of the source. Sometimes I think I smell burning oil while driving -- not the smell of oil burned with fuel, but the smell of oil dripping on a hot manifold or something. Is it possible that at higher (as in highway driving) RPM's, pressure in the crankcase is enough to push more oil out of the leak source and cause the "oil consumption" problem on my car? I'm not sure where to start tightening bolts or if that would even help. You guys always have good ideas and I thought someone might have some thoughts on this. Thanks in advance!

Lexmus

Install an oil catch can between the PVC valve and the intake. I used one of the ones in the link below and found the can filled up fast when driving over 70 mph and lesser amounts in around town driving. Thus the rear valve cover was to blame, and after I switched to the new valve cover the oil consumption radically decreased. Note I had also put in a new PVC valve as well to eliminate that variable.

The oil leak could be a valve cover gasket leak, or possibly a camshaft seal. Unless you are seeing major oil leaking on your driveway, the measurable loss you are seeing is probably due to the valve cover, especially since you say it is much worse at highway speeds. You should be able to run a paper towel around the perimeter of the valve covers and see if they are really wet with oil, and where.

fastnoypi

definitely consider changing your valve cover to the newest compatible style as found in the rx330. It may be risky tightening your valve cover bolts if you have old gaskets, the bolts have a light torque setting and may snap. The replacement job is more tedious than hard but can be overwhelming if you are an inexperienced.

ukrkoz

It's PCV valve.Positive Crankshaft Ventilation. PVC is plastic pipe material. Poly vinyl chloride.

Right hand leak above oil pan - presuming your right and my right are same, as in - engine front - is main seal. We had that leak on our 99RX and had it replaced under warranty. Other leaks, as posters mentioned, are valve cover leaks.
Valve cover leaks are not really high oil pressure leaks though. Oil under valve covers is splash lubrication. High pressure leak is usually blow by burn out. Either caked piston rings or bad valve stem seals. It'll show itself in grey smoke puffs when you step onto accelerator pedal at hwy speeds. Have someone drive your car and do it, while you tracking behind in another vehicle. You'll have to clean rings and replace seals, if that's the case.

trhs75

Thanks, guys! I should have mentioned that I have replaced the PCV valve just in case. Lexmus, do I need to plug the intake if I can get a catch can in there somehow? I think I can manage replacing the valve cover if needed. I've watched the excellent video on this forum. It looks time-consuming but manageable. Ukrkoz, I should have specified passenger side to be clear! If I'm facing rings and seals, that will be above my pay grade and I'll have to take it somewhere!