Multiweight Oils: More Protection
Question: You recently recommended multiweight oils as being superior to straight weight oils. I believe in a mild climate, a multiweight oil is inferior because it does not have the stable viscosity characteristics of a single-weight oil.--P.C.R.
Answer: Why not carry the argument one step further and run your engine on unrefined crude? The simple answer is that without additives, an engine would be a wreck in only 1,000 miles.
Many purists disdain multiweight oils for their cars, believing in the simplicity of a single-weight oil. For the layman, a multiweight oil has additives that prevent it from thinning out as the engine heats up.
Multiweight oils are given a numerical rating by the Society of Automotive Engineers or SAE. An SAE 10W-30 oil, for example, exhibits the characteristics of a light 10-weight winter oil when the engine is cold and a heavy 30-weight oil when the engine is hot.
The so-called viscosity improvers that refiners add to oil to achieve this performance once degraded over time, so that the oil eventually failed to perform as a multiweight. More recent improvements have made them sheer stable, meaning the improvers are not “sheered” apart by the rotating machinery of the engine.
And finally, the petroleum base of a motor oil will typically break down long before the additives. Most oil experts believe that a multiweight oil provides a large measure of protection to an engine beyond that of a single-weight oil.
Q: I recently replaced the timing chain and gear on my 1984 Ford Crown Victoria. Twice, I had the timing set by a Ford dealer and twice it jumped out of correct time. The Ford garage said it can’t find anything wrong. Would you please tell me what is causing this problem?--L.B.
A: If the valve timing has jumped twice, then the chain and gear were not properly installed. The timing chain transmits the motion needed to open and close the cylinder valves. The chain runs between two gears, one mounted on the crankshaft and one mounted on the camshaft.
The two gears, which are roughly five inches in diameter and two inches in diameter, are only about two inches apart. So, the chain is relatively short for the size gears that it drives. If the chain is actually slipping, it must have far too much free play.
In addition, a slip in the valve timing could cause very serious damage to the engine. It could bend a valve or damage a piston, requiring a major engine tear-down and rebuild. Perhaps the mechanics who worked on your engine are inadequately trained or poorly motivated.
