Oil 3.0 V6 again

I think more to the point, there are now NON-synthetic oils that show lower metal-removal rates in oil analysis than synthetic oils do, so saying "use dino oil during break-in" is a bit meaningless. "Break-in" is still a very real and measurable process regardless of what advertising glossies say. It never has really demanded all the special treatment that has been hyped about it,at least not since the days of cast-iron pistons in the 30s and 40s, but all engines do go through a break-in process that really extends to about 10,000 to 15,000 miles.

As a side note, metallurgy and machining as it pertains to the wearing parts of engines really haven't changed nearly as much as most people might think since the mid 60s, if you look at the clearance and finish specifications they are essentially the same then as now with a few exceptions. Even though cylinder blocks are now predominantly aluminum, sleeves are still nickel/iron alloy and rings are iron, chrome, or moly. One thing that HAS happened is that some manufacturers (Chevrolet division engines from GM for one example) are using hypereutectic pistons with very short skirts, which demand a much tighter fit in the bore than traditional cast pistons. The short skirts reduce friction, and the hypereutectic material expands very little allowing (NEEDING, in fact) a much tighter piston-to-cylinder clearance. However, it seems that hypereutectics are so demanding in fit that quite a large percentage of mass-produced engines leave the factory out of spec and have audible piston slap. But rings and cylinder walls, bearings and crankshaft journals are still very similar to what they've been for 40 years. Its a very mature technology, oils have changed FAR more than engine materials.

Many aviation engines are very different beasts than car engines. Silver based bearings are still commonly used, and automotive motor oil will make short work of them, among other problems.

I *think* I remember some testing that indicated that synthetic wouldn't cling to vertical surfaces as well, and that caused excessive wear in the thrust bearings on some engines. But that was an old, old, OLD study from when Mobil 1 first hit the market, and I don't think it has any bearing on modern oils at all.

Which non-synthetic oils?

Matt

It must be a pretty minimal difference as my Grand Voyager is approaching 150K miles on Mobil 1 with no apparent problems.

Matt

IIRC, at least one of version of Castrol GTX and (believe it or not) one Pennzoil formulation are turning in great numbers that are comparable to and sometimes better than synthetics. A few others too. You can hunt around on bobistheoilguy.com and see some of the analyses that people have posted there to be sure, I haven't spent an afternoon wading through all the info over there in several months :-)

That rings a bell. The no clinging to vertical surfaces would go along with poor film retention. We may have read the same thing - time frame (early Mobil 1 years) would be about right - my teenage Popular Science reading days.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Any idea if this was an issue simply of the viscosity of synthetic being lower when cool thus allowing the oil for drain off the vertical surfaces more quickly, or is it a more fundamental chemistry issue? I haven't heard of this being a problem anytime in recent history. I wonder if it was a real issue that was corrected, or just another of the urban legends about synthetics, like leaking seals, etc.

Matt

It is more than viscosity - more to do with surface tension or whatever - Regular oil is "wetter" than synthetic so it tends to cling to the surface rather than bead upand slide off. At least that's how it was described to me.

Hey - it was in Popular Science, so it must've been true, eh? 8^)

Seriously - I'm not sure. These were supposedly engines that were used in real-world severe conditions (fleet or taxi service IIRC - to speed up the results) with non-synthetic controls. Study and teardowns performed by supposed lubrication experts, article included photos. That's all I remember.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")