Burning Oil!



I have a 2001 Lexus RX 300 that is burning oil almost faster than I can put it in the car. I have taken it to two mechanics who could not figure out the problem. Both said that there was no sign of a leak and that they could not see any blue smoke from the exhaust indicating that the oil was burning up in the engine. I am in need of help!


How many miles before you must replace one quart of oil?

Oil being burned is usually hidden by the catalytic converter, which burns the smoke, until the oil consumption becomes excessive or the converter is plugged up.


I haven’t quite figured how many miles per quart. I did fail to mention that when the oil gets low the car also makes a clicking noise that kind of comes and goes.


I have to wonder about the “mechanics” who can’t understand this. There just aren’t many places for the oil to go. If it isn’t leaking, and the oil level continues to drop, then it has to be burning. There aren’t any other options.

Many mechanics, and some manufacturers, are willing to say that oil consumption is acceptable as long as it does not exceed one quart per 1,000 miles.

I’m not saying I agree with that, but in many cases it has become the acceptable limit. VW comes immediately to mind when I think about this issue, but I don’t read a lot of complaints about Lexus vehicles burning oil.


It is definitely way less than a 1,000 miles. I have had to add oil after a few hundred. I am wondering about their diagnosis as well. So you believe it to be a problem with the catalytic converter?


No, the converter masks the oil burning problem but it will quickly become plugged up by the constant exposure to oil.

The first thing you want to eliminate is crankcase venting problems.

A compression test followed by dry and wet leakdown test may show if it is the rings but that is not always definitive.


No, the converter is doing its job, but if the engine is burning oil the converter will become plugged up, and then it won’t do its job any more.

The problem is in the engine. I don’t know what the problem is, specifically, but the first thing to do is figure out where all that oil is going.


Thanks for your help and advice. I will proceed from here and post the problem when I find it if you are curious.


Check the PCV valve. A stuck PCV can pressure up the crankcase and cause oil consumption problems. It’s easy and cheap.


Make sure your have the correct PCV installed as well.

This is listed as a possible problem in Ford trouble shooting tables for oil consumption.


I’m wondering of the RX300 has the engine prone to sludging and the oil rings are gummed up. That won’t show on a compression test, but would cause excessive oil use.

Try some flush product made for desludging the oil system from the parts store. Follow the instructions to the letter. Post back and tell me if that improves the situation.

Note to friends: while I don’t generally recommend additives, this case is the exception, but I openly welcome other perspectives.

  • mountainbike


if worst comes to worst you might have to get new rings