I changed from conventional 10w-30 to 10w-30 syntec a week ago and now my engine knocks. I have to turn the car off for a few seconds and restart to get the knocking to go away. It only does this when the engine is cold. I've checked the oil level several times but it's at the max line on the dipstick. Any ideas?

 

don't know this one. never heard of that happening. the syn oil should not make a knockin noise. If anything it would sometimes eat some seals and leak. I talk to wanna the techs at work that know more than me and post an answer tonight or later today.

 

sry for the wrong spelling my bad typing in a hurry

 

I have the same problem, have had it for years, the car always had dino-oil, when i switched to Mobil syn oil it kept on doing it. Doesn't seem to affect any other time other than start-up, but a fix would be nice !!

 

Im running mobile 1 yet mine doesn't do that. hmm Hopefully somebodies knows at work. My professor says he doesn't know. But then again he has never put syn oil in a car before. He says though the oil should do that and that it could be another problem.

 

Synthetics DON'T eat seals.

What filter did you use?

 

on some older cars the seals on them cant handle syns. was proven on some discovery channel special I had to watch at school. I used mobil 1 filter

 

It was synthetics developed in the 1970s. All modern synthetics are petroleum based compatible.

 

I used the mobil pur 1, the expensive one. It's almost like a pressure problem rather than the type of oil. During startup the valves don't get any oil when cold. But if i wait a minute and restart it goes away after a seconds.

 

I have heard of switching from conventional oil to synthetic gradually. Like the first time use 3 quarts reg oil and 1 quart syn. Then the next time use 2 quarts reg and 2 quarts syn and so on. I heard that switching all at once will let the synhetic oil eat up all the gunk in the engine and let it clog some small oil gallies.

 

The problem lies in the detergents that some synthetics have.
The detergents clean out the deposits that are on the seals and keeping them from leaking.
That is the fact behind the don't use Synthetic in the old car rule of thumb.

 

I have seen some VG motors with some pretty dried up valve trains(heads). Over time, the oil passages leading up to the heads get smaller and smaller. Another reason to perform regular oil changes.