Lots of thoughts on this issue: Ill give you my side.
I have had lots of old iron. 57-and 60 Harley, 68 Vette 427, 71 El Camino 454, 75 and 77 Pontiac trans am (455 and 403), 70 Cuda six pack, etc, etc. Now a dated 68 440 in my 71 Cuda.
Bottom line: If I have just rebuilt a motor, I go synthetic (full synthetic all the way). I dont do the dino first, then synthetic as recommended by some: I have never had a ring seat issue, or some of the other rumours that went along with having to use dino first after a rebuild: With dino I go about 5k between oil changes. Why not?. And full synthetics have superior lubrication properties and viscosity protection, period.
If I inherit an older engine with high miles, I do the same. The old saying, synthetics will cause oil leaks is just that: An old saying. I have had motors (60's- 70's) with 80-90 k on them when I got them, and at my first due oil change I went synthetic. And it NEVER caused an oil leak. I use synthetic pre mix in my 1983 Yamaha YZ490 dirt bike. 2 strokes cant hurt from synthetic
But, I can only guess this point: If one already had an oil leak with dino oil, synthetics may, I say again, may, aggravate a pre existing oil leak. No proof here, just assumption
The only time I use dino oil is in my chain saw pre mix, and my 1932 Ford 9N tractor that leaks like hell to begin with
Its been proven over and over the superior viscosity and lube protection of synthetics in engines. HP TV did a test on drive line syntheticss used in 4 speed trannies and rear ends, with dino proven HP gain.
Cost: If you look at what it costs for 5 qts dino oil changed at 3k intervals, and synthetics changed out at 5k intervals, the price doesnt vary much between the two after 4-5 oil changes. And the unseen engine wear saved certianly pays for itself in any price offset using synthetics
I have read allot of articles on dino vs synthetic: The net is great: Its just hard to beleive what: I have to go on mixture of what I read, and my personal experinece
One thing I WOULDNT use, are synthetic BLENDS that I see out there. I dont have any experience on those
