I took my car in about a week ago and had them check out this leak I thought I've been having. Finally they found oil in the air intake and cleaned it out. The explained to me that my loss of oil (1 quart every 3 weeks) is caused by "blow by".

So my question is what can I do reduce blow-by? Is there some kind of fuel or oil additive? I'm currently using Mobil 5w-30. I have about 129k on my 99 GS300. All help is appreciated. Thanks.

 

are they sure its motor oil? What filter are you using?

 

I take it they did a compression test?

The crankshaft vent system for instance in my RX300 will reroute gases in the crankshaft back through the air intake (after the air filter) but before the intake manifold. And every so often I go in there and clean it.

The one additive I know offhand that has some effect is Restore, but that depends on just how much blowby you have and what other mechanical issues you got going, particularly the piston rings.

 

Yes they noted that it was defintely motor oil. Not sure what filter I am using. Pretty sure it's stock. What filter should I be using?

 

Thanks for replying. They did not do a compression test. Lately I've been putting 1 quart of oil in about every 3 weeks. I'm not sure exactly how much blow by the equates to but they did not say it was a large amount they cleaned out.

 

1 quart is quite a bit of oil to be loss through the system. Usually a blow by happens when your piston rings are pretty much worn out or the PCV system is clogged.

worn piston rings will create an excessive pressure in the crankcase, and a non-functioning PCV system wont recirculate the vapor, therefore increasing (positive) pressure in the system. What I would do first is to check your PCV valve (Positive Crankcase Ventilation).

Usually the valve is located on your valve cover. I do not know where it's located on a GS300 so maybe someone else can tell you. You can simply pull it out while the engine is running, and put your fingers over the PCV hole. If you get suction, then you're PCV is fine. If not, replace it. It's pretty cheap anyways.

 

blowby, is when the piston reaches the top of the compression stroke, and some of the pressure between the top of the piston and the top of the combustion chamber goes down and around or "blows by" the piston, due to a bad seal against the cylinder wall via bad piston rings.

 

I didn't see it at first, but you may want to try something other than Mobil 1 5W30 in the future for the amount of mileage you have as I know quite a few people who have consumption issues with that down here after they go over 100K miles or about 160 kms. However, Mobil 1 5W30 is the one synthetic here that is sold like tacos on the street corner, so people will use it. I like the German Castrol 0W30, but am currently testing out a 10W40 Redline.

The compression test would help because if you've got scratched cylinder walls or issues with your piston rings (such as deposits or wear), then blow by is going to continue to get worse over time until properly diagnosed.

Again, Restore may or may not help in the situation, www.restoreusa.com

 

So it looks like I'll be checking the PCV valve first. Not sure where that is or how to get to it. So I'll probably have to take it over to Tuffy. The next thing I'll do is get an engine compression test and maybe even a leak down test. Does anyone know how much these cost and a good place to get them done?

 

Update

Following my last oil change. I noticed that the time I have to put a quart of oil in has increased to about 5 weeks which is better than 3 weeks. I put a quart in last Friday (3/21/08) and just had the pcv valve replaced today. I had the dealer look at the service history to see if it has ever been replaced and it hadn't. So essentailly it was long overdue. Hopefully this fixes the issue. If not my next steps will be:

1. engine compression test and leak down test.

2. try 10w30 or 10w40 motor oil

3. try engine restorer if dealership techs approve

Hopefully it doesn't get this far.

Wish me luck with checking my oil over the next few weeks!

 

How do u know if you have this problem?

Do you see a puddle where you park?

Where is the leak?

 

The dealership checked it out and told me that my issue was blow-by. This would explains why there haven't been any visible leaks, yet still a loss of oil.

 

There is another additive I used successfully in the past month from Liqui Moly, http://store.interautopartssd.com/mo...3d606346c9a122 (only place I have seen it sold in the U.S.)

Whatever issue I had with my compression, it is now gone.

 

Thanks, LexMex. I think I'll try that one over the Restore after reading the following thread:https://www.clublexus.com/forums/sho...light=restorer

I hope I can put this issue to rest within the next month.

 

There is a similar problem which involves disappering power steering fluid with no visible leak or puddle on the floor where the car is parked. This can be caused by a bad valve on the power steering hose. There is a vacuum line that advances the engine RPMs slightly (opens the throttle) when the steering wheel is turned while at idle. If the valve fails, power steering fluid can be sucked into the intake manifold and burned off with the air/fuel mixture. Results in loss of fluid with no visible leak.