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Old 10-22-2018, 11:57 AM
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simplyconnected simplyconnected is offline
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15W-40 means, 15 viscosity in WINTER, not 15-weight. With regular oil changes, I never heard of oil that 'gums up' an engine. Old oil, loaded with acids and ash will gum up (especially hydraulic lifters).

Back in Squarebird days, all oil was labeled, 'Motor Oil'. Detergent Oil didn't exist yet so it was all, Motor Oil. Now, we call it, 'Non-Detergent Motor Oil' and it's hard to find. Oh yeah, it contained loads of zinc and phosphorus in the form of ZDDP. As engine oil gets cycled through your engine, the ZDDP is consumed, then it's eventually gone.

For a while, GM sold ZDDP supplement through their dealerships. When they stopped selling it there was a 'run' that quickly sold out every case available by guys with classic cars. Flat tappets need the same ZDDP that destroys catalytic converters. Since the EPA always wins, automakers compromised by using hydraulic roller cams (with NO flat tappets). That ended the need for ZDDP.

Now, all the fluids your classic car was designed and built for, do not exist. Gas has no lead (needed for valves) and 10% is alcohol (that attacks carb and fuel pump parts). BTW, gasohol has lower BTUs than gasoline so more fuel is needed.

Is this a bad thing? Not if your engine is built to run modern fuels and lubricants. Our entire exhaust systems used to last maybe 4-5 years, tops. Spark plugs & points, 12,000 miles. The whole engine, 80,000, and valves used to load up with lead deposits if the engine wasn't 'blown out' by taking a long trip. Car body steel was thick, to withstand salty winters because factory paint was poor.

Not any more. But... if your classic car runs on today's liquids there needs to be supplements or longevity will suffer. - Dave
My latest project:
CLICK HERE to see my custom hydraulic roller 390 FE build.

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