1950s Synthetic Oil from Valvoline

[The Tassie Devil(le)]

Isn't it only Lead that affects Catalytic Converters?

Bruce.

[Jeff Rosansky CLC #28373]

Isn't it only Lead that affects Catalytic Converters?

Bruce.

Well, I thought zinc did too. I'm not sure.

Jeff R

[TJ Hopland]

Damaging cats was one of the reasons they say they reduced the zinc levels.  I think its an overall evolution thing.  75 the engine and cats were both relatively crude so the zinc in the cat wasn't really hurting anything.  As engines got better they were able to make cats better and that was when the zinc became an issue for the cats and luckily by that time most new production engine didn't need the zinc so they reduced it.

Could you overdue it? I'm sure you could.   

[Chopper1942]

Zinc and phrosphorus are/can be CAT killers in high doses. that's why most high ZDDP oils are recommended for off-road use only. No CATS! I have posted several times about using ZDDP and synthetic oils in older vehicles. Mobil 1 20-50 is one of the lower cost readily available. >$30.00 for 5 qts. at Walmart. Valvoline and Pennzoil also have oils. go to the manufactures web sites and check out the specifications for oils to use with flat tappet cams.

[David Greenburg]

I don't think there is any question that synthetic is a superior lubricant, and I use it in all my newer vehicles. However, I don't use it in my old Cadillacs. First, they have a very gentle "lifestyle," being driven gently and only in dry weather for maybe 1000-1200 miles/year, and I change the oil annually, so the extended miles between oil changes is meaningless. Second, like most old Cadillacs, they have some incontinence issues, which I'm afraid would only be aggravated by using synthetic, with its smaller molecules. In recent years, I've been using either Lucas hot Rod oil or Rotella T4. If I had a freshly rebuilt engine I might consider using synth. From the get-go although I'd still be worried about leaks due to the larger tolerances in these old engines.

[Chopper1942]

If you want to know all about oils, go to Lake Speed Jr's You Tube site. He will tell you more than oil than anyone else and it is not biased by brand sponsorship.