Good question.
The answer is that both ring and cylinder surface finish technology has come a long way since 1955. Modern rings will seat using synthetic oil, but old beliefs die hard.

Larry
code5coupe

 

Everyone on this forum should read these two articles on modern basestocks.

http://www.machinerylubrication.com/...up=OilAnalysis

http://www.machinerylubrication.com/...p=Lubrication2

What is Castrol GTX made from anyway? We will never know, but I have used at least 100gallons of it with varied success.

 

Rod, what does "varied success" mean?

Thus far, I've used Castrol GTX from initial break-in and 3 quick changes, thru 2 more changes over 6,000 miles. I'm at the point that I can either switch over to a full synthetic or stick with Castrol. With 6 mo./3,000 mi. changes (I'm dogged with oil changes), what's the benefit of going with full synthetic like Mobil 1, with normal somewhat "normal" driving habits? As you could see in a previous post by the Amsoil dealer, Castrol GTX has damn good test rsults across the board. I read that report last year, thats why I went with Castrol for the entire engine break-in period.

 

My earliest experiences with Castrol GTX were excellent. It replaced the Quaker State that turned to black water in my tow rig. But all the engines didn't stay clean, and I had some crank wear that I didn't particularly like. Overall the GTX did a good job in the wear department, but could have been better in the cleaniness area (death of one engine).

But all that doesn't matter in the least since GTX is totally different than it was just a few years ago. Castrol is a blender, so you can't really tell what they are using as far as the basestocks and additive packages are concerned from year-to-year or oil-to-oil.

It seems that the API-SL rated oils were the worst that we have seen lately since the antiwear additives were lowered, and HP flat-tappet cams suffered greatly. The API-SM oils are formulated differently, with more reliance on having tough basestocks than before. As a result the best conventional oils have closed the gap on the synthetics as far as the basestocks are concerned. Read the links.

So which conventional SM oils are good enough for a performance engine? I don't plan on being the one to find out. Indications are that the newest Chevron-Texaco oils like Havoline and Delo 400 are tough as nails, and give lower wear results than many of the traditional synthetics. But I am sticking to synthetics and potent blends until all are proven.

You should try the Castrol Syntec 0W-30 from Autozone (says "Made in Germany" on the back at $5.19/qt) and change it once a year if you drive 6000 miles or so. It can go longer or shorter depending on how hard you stand on it. It is a long-life spec oil for Mercedes and others, and is very smooth in the crankcase. Wear numbers are pitifully low. If that seems too thick you could try Pennzoil Platinum 10W-30. I am trying the Platinum now and it seems to be holding up well to my horrifying driving. It is also very, very smooth in the crankcase (and $4/qt). Both are new-age formulations.

For lower-cost conventional oils use Havoline, Pennzoil, Castrol GTX for lower performance driving with intermittent blasts. For more radical flat-tappet cam engines use the heavy-duty engine oils and/or the best synthetics. For race engines use the race oils. Amsoil also makes a highly competitive oil from a performance standpoint in every niche.

 

Thanks!

FYI, using a fellow forum member's 99 C5 as a test mule, I did a comparison of the German Castrol vs the AMSOIL Series 2000 0w30. For those that prefer an American made alternative to the GC, the AMSOIL proved to be viable:
Used Oil Analysis Comparison: German Castrol 0w30 vs AMSOIL Series 2000 0w30

 

I have read soooo much stuff about motor oils... my statement was seriously simplified for the context of the post.

I will take some time and read those articles. Your other post is very interesting.

 

That is a truly impressive set of wear numbers for the Amsoil 0W-30. It is hard to beat "pitifully low." GC may end up being made elsewhere depending on economic factors, so it's good to know where to get an equally performing oil. I've always admired AMSOIL for their "no holds barred" oil fomulations. I can't say so much for Mobil 1.

 

Rod, thanks alot for your insightful comments. Excellent. Looks like I'll be a convert; now's the time, early in "new" engine life.