Synthetics and increased engine noise

What do you gentlemen have to say about changing to synthetic on an engine that has always been run on regular motor oil and noticing increased engine noise?

My father has done this on 2 different engine, a 4.9L Ford inline 6(with few miles on a rebuilt engine) and on a 350 Chevy engine from a truck.
In both cases there was actually increased engine noise when switching from 10W30 regular motor oil to synthetic.
The sythetic is supposed to be better at reducing wear, but does it provide the same cushioning effect by filling in the spaces between the rod bearings and cranshaft journals?

In your opinion is this extra noise harmful? To me extra engine noise means more metal hitting metal.

I'm sure some people here will say they use synthetic and don't notice any noise at all. But I bet if they were to fill up with regular motor oil of the same weight at the next oil change, they'd notice the engine got quieter.

Can some of you provide feedback regarding your thoughts on this?

Thanks,
MAP

Oh, just postulation, but...

Synthetics are known to sometimes wash crud out that mineral oils leave behind. They're also known for better viscosity stability with temperature changes.

In my own non-Jeep experience, switching my new-to-me Y2K Dakota 4.7 over from who-knows-what to Mobil 1 at 68K miles, it did visibly wash some stuff out with the first batch of oil (i.e. got very dark very quickly). Now, I could swear it is quieter at idle, but I can also now hear a lifter sometimes if I'm driving near a residential fence wall with the RH window down. Maybe it washed some crud out of a weak lifter. Maybe it unmasked a noise that was already there. Maybe I'm just hearing things.

I will make a claim, with some conviction, that it's quieter at startup, and the pressure pops up right away. This is what I wanted to use a synthetic for.

Yes, this is all subjective and unscientific, of course. Measurements of the sound, and what individual sounds represent, would certainly be of interest...

Actually the sludge thats in there will act as a sound dampning materal, when you remove it the sound dampning is removed. The other side is that it silenced some other stuff from the total noise and is leaving the stuff that makes more noticeable sounds. On my 98 I can hear the injectors clicking...

RichP said:

On my 98 I can hear the injectors clicking...

Click to expand...

Same here. When I open my hood with the engine running, the most prominent mechanical noise that I hear is the injectors pulsing. I most definitely think my engine is quieter with Mobil1 in it's bloodstream.

For example:
Recently, I changed my head gasket. I know I knocked some crud down in the oil galleries in the process. When I put it all back together, I just dumped conventional oil in it, with plans to change it back to Mobil1 after a couple days of driving. (Just wanted to get all of the loose crud picked up in the filter and then dispose of it.)

During the next day or so, I swore the engine was more noiser than normal. But I just wrote it off as paranoia. Then, I pulled into my firend's driveway one night to pick him up to go somewhere. When he got in, the first thing he said to me was "your engine sounds different... kinda clattery." I said "yeah, I don't know what it is."

The next week, I changed it back to Mobil1. Went back to the same guy's house a few days later, he was messing around in the garage so I left the engine run and went to see what he was doing. We were standing there talking and he looked at the Jeep and said "sounds like you got that noise fixed, what was it?" I shrugged and said "I dunno, I changed back to my normal oil and it went away."

I know it sounds a little far-fetched, but its a true story...

Also keep in mind that Mobil 1 is one of the thinnest 30 weights on the market. Mobil 1 5w-40 is a better choice for the 4.0 IMHO, that's what I'm running this summer.