Will synthetic oil cause clutch slip?

[koolaid_kid]

O.K. I have the original engine out of my TransAm sitting on an engine stand in my garage. (I replaced it with a fully forged turbo engine.) It has 40k on the clock. I pulled the heads off and there are still cross hatches in the cylinder bores. It spent 20k on a 5 p.s.i turbocharger. Using conventional oil. So, I will always use conventional oil, but certainly feel free to use the synthetic if you wish.

 

[tkent02]

I have seen several high mileage engines with all of the crosshatch visible, an Opel at over 350,000 miles, several BMWs at 2xx,000. My first GS550 at about 120,000. Even the rings were not worn at all on the 550.

I have never seen this on engines running non synthetic oil. Usually they are through the cross hatching and actually have a wear ridge before 100,000 miles, although the modern FI engines probably don't wear as fast.

Still I run the regular Rotella in everything now, I don't end to keep things long enough that I care all that much about engine wear.

 

[Guest]

O.K. I have the original engine out of my TransAm sitting on an engine stand in my garage. (I replaced it with a fully forged turbo engine.) It has 40k on the clock. I pulled the heads off and there are still cross hatches in the cylinder bores. It spent 20k on a 5 p.s.i turbocharger. Using conventional oil. So, I will always use conventional oil, but certainly feel free to use the synthetic if you wish.

Actually I use both, synthetic in the 1000 and conventional in the 1100 since it's more prone to weeping running at higher temps. But I did use Mobil 1 in my Skunk in '79 when it was a fairly new commodity, and for the life of me I couldn't figure out where the oil went, didn't leak, just dissapeared. I used it during my x-country trip and when I took it to the shop for a check-up I asked the mechanic about synthetic oil. He looked at me and said, "where does it go?" so I changed back to conventional. I figured it just blew it out the breather.

 

[koolaid_kid]

I have read that synthetics have a higher tendency to leak thru small cracks than conventional oil, but I have never seen statistical data to back it up.
I have a friend that owns a 2002 WS-6 TransAm and he won't use anything but Mobil 1. Personally, I believe the owner should use whatever gives him the most peace of mind. At least for cars, for bikes most certainly diesel oil due to the fact that it also lubricates the transmission and can't use "energy conserving" additives for the reasons already posted.

 

[Nessism]

Synthetic oil is more temperature stable, thus a thinner base stock can be used to build a multi weight oil compared to mineral oil. For example, Rotella synthetic is 5W-40 (using 5W base stock) but the mineral variety is 15W-40 (using 15W base stock). I think it would be difficult (expensive) to build a 5W-40 mineral oil that met the same requirements as the 15W-40 variety.

Because the 5W base stock is thinner than 10W or 15W oil, it will exploit sealing voids more easily. Also, synthetic oils by virtue of their viscosity stability, can be run for an extended drain interval compared to mineral oil. Oil designers knowing that often include more acid buffers and detergent into the base oil to compensate. Extra detergent may loosen sludge plugging leak paths too.

As for synthetic oil reducing friction, I'm not so sure. I believe they do under high heat conditions, and during extended drain intervals. But I don't think they do much of anything to reduce friction other than they are often lower viscosity, which does reduce friction when the engine is cold because it flows better. Under normal running conditions I don't think synthetic will reduce friction compared to mineral oil all things being equal.