My 99 2.8 30V runs smooth and quiet when the engine is cold. Once the oil temp starts to go up, the engine starts to sound like a diesel. It only sounds bad at idle, and has been doing this for some time now.

My guess is that when the oil warms up and the viscosity thickens, the lifters are not getting as much oil as they do when the oil is cold and thin?

I am using 5-40 synthetic.

Has anyone had this issue? What do you all think about seafoam in the oil to clean up any sludge that might have accumulated?

I was also considering using a lighter weight oil?

Any suggestions??

Thanks, Eric

 

Oil is thick cold, not thin.

You should try a heaver weight oil. Check your chain tensioners out too.

 

Actually you are wrong......

I am an Amsoil dealer so I am very educated about oil.

The weight (film thickness) of 5-40 oil is 5 when cold and 40 when hot.

Oil flows better when it is hot, but is actually much thinner when cold. The additives they put in oil are responsible for the change. This was the reason for the invention of multi-grade viscosity oil. The oil is made thin to flow in cold weather, and then the added compounds thicken the oil as it warms up to provide a thicker film to protect the engine parts. This range in viscosity is the reason the owner's manual warns about operating at higher RPM's until the oil temp gauge goes up. In the 1.8t which has commonly seen sludge build-up, the hotter the engines get, the louder they rattle. You can find video's on "YouTube" where people are showing what their 1.8t's sound like when they warm up with sludge. The noise sounds similar to my 2.8 that's why I believe I have a sludge/blockage problem.

 

^^ okie dokie...

 

That Amsoil oil education they give you folks really convices me to use anything else but Amsoil...

 

Doesn't sound like an oil issue at all. Wish I had more to offer.

 

Well.. he's BS'ing anyways...

 

This post challenged my thinking about oil viscosity.

Like Midniteoyl I always thought that all automotive oil was thin at high temperatures and thick at low temps. I also thought that although multigrade oils were thinner at low temps they still became thinner as they heated up.

I did a little research into oil viscosity and found that ejb is full of crap when he disagrees with Midniteoyl. 5W at low temps has a higher viscosity than 30 weight oil at high temp. In fact all the multigrade oils have higher viscosity at low temps than at high temperatures. Ejb does a double talk – he said that “Oil flows better when it is hot, but is actually much thinner when cold.” Viscosity is a measurement of flowability and thinner liquids (lower viscosity) flow better.

Film thickness is a different issue… It is not viscosity or weight of the oil - although it can be connected. The polar bonds in the chemical chains determine the thickness of the film that is left on the metal in a motor. Longer chains make thicker and stronger film while shorter chains make them thinner. Heat tends to break down the bonds and the chains get shorter so the film thickness is less.

Again ejb is full of it….