Burning oil at start up

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I just had the heads and cams replaced on my 98 mustang gt. All the intake/exhaust valves and seals are new. The whole upper part of the engine is new. I have driven the car 300 miles since i got it back and i notice when i first start it up there is no smoke but if i drive it for a little then start it up again after sitting 5 min i get a puff of blue smoke, and if i keep restarting it over and over it does it every time. It does a little puff of blue smoke when i get on the gas and let off but then it is all clear....even when idleing. My mechanic informed me he filled it up with citgo 10w40....dino oil....i usually fill it up with 5w30 mobil 1. I am going to change the oil tomarrow with dino halvoline 5w30 then go back to synthetic. Do you think the oil is the cause? or could it be the valve seals that are brand new!?
 
When oil is at ambient temp, it's thicker than when the oil is in normal engine operating temperature.

In this case, your intake/exhaust valve guides or valve guide seals are in question (yeah, even you tell me that the seals been replaced but are they installed properly??)
 
You are absolutley right. I changed it back to 5w30 and now it is more evident. Bringing the car back. Let you know the final outcome. thank you
 
I got the car back and everything checked out ok. We pulled the vavle covers and all the seals are fine. I always ran synthetic and now have dino in could this cause it? The plugs were pulled and were fine.
 
synthetic motor oil just happens to have a higher burning(combustion) temperature than that of ordinary dino oil, thus the possibility of lower/less smoke-like exhaust coming out.

The logic goes like this:

(if your engine has oil burning issues)

if previously running dino oil and it smokes-->switching to full synthetic oil

observable outcome: less "visible" smoking due to higher burning tempurature with synthetics.

If prevously running synthetic oil and no "visible" smokes---> switching to dino oil it "smokes" more

this is due to dino oil's lower combustion temperature, while all other things being equal.


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This does not necessarily mean that your valve guides are in good shape. (seals fine means nothing in this case). Excessive clearence on valve guide bore will cause excessive oil leaking past the internal bore, regardless of how "good" your valve guide seals are.


Granted that you do not have any excessive crankcase pressure (meaning that your PCV part is functional and no excessive blowby causing excessive crankcase pressure), your last likely cause should be worn valve guide bores. To properly service them is to send the head to a shop and press in some new ones.

Oh and BTW: old tricks die hard: don't consider "reaming" the internal bore with screw-like ridges just to shrink the internal valve guide bore a bit. This is an old hat's trick that will only lasts approx.3000miles before your engine starting to smoke again.

p.s. plugs may not show any significant signs of oil burning due to extreme combustion temperature (unless your motor oil is of high-ash variety or your engine is burning 1qt every 300 miles).
 
I agree with the above statements, your valve guides are definately in question. That's a nice way of saying they're shot.
wink.gif
 
son of a b*tch. I know they are too. All the guys in my mustang club were telling me they're shot. They were driving behind me and choking everytime i got on it. Bringing it in first thing monday and getting the valve guides re-done even if they are "brand new"!!
 
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