Unless I missed it somewhere....I did not read where you used an engine flush before switching over to synthetic....?? When I switched my diesel engines over from conventional to Amsoil, I was told to use the engine flush that Amsoil sells to help clean up the cylinder walls and all from the contaminants.

They said to pour the flush in with the conventional oil and run the engine for either 20 or 30 minutes (cannot remember) and (do not drive with the flush in the engine) but after the run time, drain the engine and then put the new synthetic oil in and my engines always looked clean when checking the oil.

One main thing I remember when I switched was that the engine temp. always seemed to run about 5° cooler with the synthetic over the conventional oil......

I would like to read that. The logic this guy is presenting, to a layman like myself, seems to make perfect sense.

I was told you could not run Zinc in full synthetic, that's why Spector makes semi synthetic with the zinc added in...

Bullpoop. The three most dangerous words are, "I was told".

Synthetic lubricants probably require different additive packages than petroleum based oils, that's true. But there are several brands of engine oil with high levels of zinc in a pure synthetic base stock.

R.

If anyone is concerned about zinc and phos in a synthetic, here is a Blackstone Labs used oil analysis for Shell T6 (synthetic Rotella) off of a BMW forum.

12,500 miles on the oil.

Kevin

Wow. Since I've had the motor in my car, I've used only Mobil 1 15w-50 along with one bottle of Comp Cams break in lube. In 5 years, I've changed my oil once. Just checked it yesterday, and it's still pretty clear. On average, I'll drive about 600 miles/year. To be fair though, the first several years it wasn't really driven at all. 2012 was the first year I started driving it more than just back and forth from a shop/garage. And that was late 2012, so I'll say 2013 for all intents and purposes.

I too would be interested in reading the other discussion.

I agree, if you're changing oil every year at 1500 miles, synthetic is a waste. That said, I wouldn't go running to change it now, I would just run it for the year as-is.

Also, out of curiosity, why are you running 20w50? Were you getting low oil pressure with 10w30 or just jumping on the "old cars need thick oil" bandwagon?

http://www.corvetteactioncenter.com/tech/oil/oil_camwear2.html

Here's a good article on zddp, even though not what the OP was was about, it came up in the discussion.

You all could have a bit of a look at service intervals on every car ever produced in the last 50 years, I have yet to see one based purely on mileage - there is a time factor in there too, this is because various parts of the oil start losing their effectiveness when exposed to heat/air/contaminates, I think 6 months OR 3000 miles is more appropriate than a year - its not like its a huge $$ thing to protect your $howevermuch to replace motor

A few thoughts,

I wouldn't stress over the appearance of the oil in such a short time. Motor oils have heat activated additives that change appearance with normal use. Nothing to be concerned about. Here's a video from GM which I find helpful in showing folks it's very difficult to judge motor oil useful life based on color alone. I'll start the video at 1:05min to avoid the marketing on GM's OLM system. -> https://youtu.be/oi_J4SZUlSo?t=1m5s

I also agree with others that 20W-50 may be overkill. Don't know the specifics of your build, but as I recall, the general rule is 9-to-10psi per 1,000rpms. You may be able to accomplish that with a decent 10W-30 and free up a pony or two in the process.

Also, plenty of full synthetics with lots of Zinc in them. I'd also agree that in a seasonal driven muscle car application, synthetic may not provide a meaningful advantage. There's lots of good options commonly available. With an old school cam grind, I'd consider a 10W-30 Rotella or even a Quaker State DEFY 10W-30. With a newer fast-rate flat tappet I'd go with the specialty muscle/race oil.

Also, there is one area I can think of where a top tier PAO synthetic may be advantageous in a muscle car application. That is PAO synthetics have shown an increased ability to stay within their viscosity grade when fuel dilution is a potential occurrence like for example in carbureted engines. But you won't really be able to tell you'r degree of fuel dilution without used oil analysis testing.

Good Luck

Who do you think came up with those oil change intervals? Scientists working in a lab for the good of mankind? Or was it oil companies/car manufacturers who make money every time you come in for an oil change?