My 99 infiniti with 123K is burning oil(1/2 quart in 1k). took it to mechanics and one guy told me to use high mileage oil(10w40)

I did some research in bobistheoilguy, seems maxlife or Penzoil is a good choice, should I go for maxlife 10w40? or should I continue to use 5w30 and keep adding oil?

thanks in advace!

suggestion to diagnose where the leak is is also highly appreciated! (piston ring, valve seal? )

At 123k and burning oil? It will be good to go get it checked out by a mechanic. You might be needing to get gaskets replaced. Engine still has a lot of life. So, will be good to address the issue first. Let us know what you find?

Thanks man, I have been doing research on this for quite a while. There is not a single drop of oil on the ground. and my car has blue smoke in the morning, especially if i park it on a slope, it gives a cloud of blue smoke. it's definitely oil burning. But I don't know where it leaks from. If it's something fixable at a reasonable cost, I'll fix it, otherwise I will replace the motor.

so any suggestion on diagnose where the oil leaks into combustion chamber is highly appreciated!

I took it to two mechanics, one said it's normal for this year old car to burn oil and suggested me to use high mileage oil; the other said it's a worn piston and asked me to get rid of it asap. I really need a knowledgeable mechanic.

Oil burining is normal (1/2 to 1 Q every 5K miles) but excessive buring needs investigation.

BTW in your post you don't mention what kind of soup it is presently running on. If the soup is not syn it is a good idea to switch!!

Check your PCV valve also!!

It's conventional oil,
Syn oil? I heard that's finer than conventional, and leaks more, am I correct?

As for PCV valve, I replaced it a month ago with a brand new one from autozone.

I was on conventional oil until 160K miles and had a leak (from upper pan or valve covers don't know, the engine oil was on my tranny). I switched to syn (SuperTech) and it has cleaned up the sludge/varnish and helped stop the leak, kind of made the gaskets come back to life.

BTW, I found running syn is cheaper than running dino, this was my calculation

Dino oil + filter is $20.
Syn oil + filter is $25.

Even if I get 1MPG saving within 3K miles I have recovered the additional cost and also have a happier engine.

Switch over to any syn, it will help control the leaks and also will reduce the burning!!!

The symptom you describe of oil smoke at start-up is typically due to faulty (worn and/or hardened) valve guide seals. Oil dribbles past the seals and enters the combustion chamber when the engine is shut down, then smokes upon start-up as the oil is burned off. Through variations of a compression test you should be able to determine whether the the problem is rings or valves.

thanks, what grade you use? 5w30syn ? or 10w40syn?

thanks, this really help, but could you please be more specific about how to determin wether the problem is rings or valves?

The basic test is to take a compression reading for each cylinder and record the values. Squirt a small amount of oil into each cylinder (by way of the spark plug hole) and repeat the test. If the reading is noticeably improved, chances are the rings are worn. The theory is that the oil in the cylinder will provide a better seal for the rings and improve compression. If there is little to no improvement in the readings, your rings are probably not the source of the problem.

There's other variations of the test, but the one i described above is easy to perform at home and it will give you a pretty good indication of the problem.

Thanks a lot! I'll do that in a few weeks and update the result.

YUP!
i too agree with you talking horse thats right on
the head on youre post

kissas you could try some Lucas oil stabiler next oil change
just add about 400ml to your oil. now its not a cure but it might help
to a degree or slow down your oil burning worth a try.??

I'd say switch over to a non-synthetic and try an auto-RX treatment. You need to clean out all the crap and recondition the seals if at all possible.

You need a good dino (conventional) oil with a lot of detergents and auto-RX, Mobil Clean 5000 is a one option:

https://www.mobiloil.com/USA-English...lean_5000.aspx

http://www.auto-rx.com/index.html - link to Auto-RX and you can read about it more at the bobistheoilguy forums.

Here are some FAQ's for Auto-RX, if you do have a valve stem seal issue this may solve your problem.

http://www.auto-rx.com/pages/faqs.htm - expand the section on valve seals.

Once all done and you complete the clean phase (auto-RX will explain if you read up on it) then move to a good synthetic like Amsoil or Mobil 1.