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Unread 09-30-2009, 05:41 PM   #1
littlefdl
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Blue smoke from Tailpipe..94 ZJ I6

I usually change my own oil but yesterday i was in a rush, so i had a shop change it for me. Today i noticed blue smoke coming from the tailpipe when i hit the gas. It's not a big cloud but before the oil change i saw no smoke at all. The shop used 5w30 and i usually use 10w30. I checked the oil and it has to be the thinnest oil i have ever seen in my life, could barely see it on the dipstick. Could this cause the blue smoke? Im changing the oil again myself tommorow, just hoping its not a valve. Jeep has 210,000 miles. thx

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Unread 09-30-2009, 06:26 PM   #2
cmonson
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the 5w30 isn't making it smoke. besides both oils are a 30weight oil once warmed up.

Blue smoke is a bad sign an issue which is probably rings.

Saying that, any way they could have drained the oil, then started the car (maybe by accident) without it being filled? I know these fast lube places sometime stick 2 people on 1 car. No one is tracking who is doing what.

do a compression test, both wet and dry.
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Unread 09-30-2009, 07:45 PM   #3
littlefdl
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i knew i should have waited and did it myself!! will run test tommorow thx!
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Unread 09-30-2009, 07:52 PM   #4
volvite
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I've seen more blown engines come out of Jiffy Lube than anywhere else.
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Unread 09-30-2009, 08:26 PM   #5
Redbob
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5w is a lighter oil cold, and if you had no blue smoke before, you need to go back to the heavier oil; in fact, depending on how cold the winters are there in NC, you might be well off going with a 20w-40 or -50.
I use 20w-50 year-round here in North Texas, also did so in Middle Tennessee and North Georgia, without any problems whatsoever - except a complete absence of oil consumption at 90K miles on the Jeep, and 175K miles on the 4.0L Explorer, and 128K miles on the Corvette. At 190K (hard) miles the BMW 7-series burns less than half a quart in an 6,000 mile oil-change interval.
So... you can listen to the folks that think you ought to be running water in your engine, or you can up the viscosity a little, and see for yourself what happens.
BTW: viscosity of an oil directly relates to the film strength, as one increases so does the other,. and if you're thinking film strength is a good thing, you're right. It's what keeps the rod and main bearings from making actual metal-to-metal contact, and serves the same function at the piston-to-wall interface. So I'm a big fan of film strength, and oil pressure generally.
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Unread 10-01-2009, 05:42 AM   #6
cmonson
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the difference in 5w is not going to cause it to smoke. period. I agree when you have low oil pressure, you should go with a more viscous oil, but it will not stop a smoking engine.

You either have bad valves or bad rings.
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Unread 10-01-2009, 07:24 AM   #7
Redbob
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Quote:
Originally Posted by cmonson View Post
You either have bad valves or bad rings.
Bad valve GUIDES and SEALS or bad rings.
And the simple way to sort this out is to see if the blue smoke occurs on acceleration (bad rings) or on throttle-closed deceleration (valve guide seals).

But a thicker oil will reduce the leakage past seals or rings; and comparing the cost of an engine overhaul to the cost of an oil change, wouldn 't you say it's worth a try?

It's a whole lot easier to make absolute recommendations like "you've got to rebuild your engine" when it's somebody else's engine, isn't it?
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Unread 10-01-2009, 07:27 AM   #8
savexourxship
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Sell! Sell! Sell!
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Unread 10-01-2009, 07:32 AM   #9
cmonson
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Quote:
Bad valve GUIDES and SEALS or bad rings.
agreed. Do a wet and dry compression test.

are you sure you didn't have this issue prior to the oil change? Maybe you are just noticing it.

another tell tale sign of worn valve seals is a puff of smoke at startup after it has been sitting for a while.

I would also pull each sparkplug and verify the condition. You may be able to locate the bad cylinder.

Now with 210K mile it would not be unrealistic for a major overhaul.

I would start with a wet/dry compression test. You have to pull the plugs to do this, so look at the condition during the process.

assuming the worst, even if it is smoking a bit, keep the oil up where it should be and you can still obtain many many miles.
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Unread 10-01-2009, 09:48 AM   #10
littlefdl
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I changed the oil this morning and drove to work, no blue smoke. I came out around 11 and started her up no blue smoke. Hit the gas a couple times, no blue smoke. Change your own oil ppl.

Last edited by littlefdl; 10-01-2009 at 11:24 AM..
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Unread 10-01-2009, 10:33 AM   #11
4jeepers
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Quote:
Originally Posted by littlefdl View Post
I usually change my own oil but yesterday i was in a rush, so i had a shop change it for me. Today i noticed blue smoke coming from the tailpipe when i hit the gas. It's not a big cloud but before the oil change i saw no smoke at all. The shop used 5w30 and i usually use 10w30. I checked the oil and it has to be the thinnest oil i have ever seen in my life, could barely see it on the dipstick. Could this cause the blue smoke? Im changing the oil again myself tommorow, just hoping its not a valve. Jeep has 210,000 miles. thx
Not good! You are burning oil, rings perhaps!
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