Be aware that your engine's fuel requirement can change with time, mainly due to carbon buildup changing the compression ratio. If your engine pings, knocks, or runs on, switch to a higher grade of fuel and check the ignition timing as soon as possible. Do not retard the timing from specification unless you still have trouble with the higher grade fuel, and then not more than 3°. Retarded timing will reduce power output and fuel mileage and increase engine temperature.
Only oils labeled SF are approved under warranty for use. Select the viscosity rating to be used by your type of driving and the temperature range anticipated before the next oil change.
The multi-viscosity oils offer the important advantage of being adaptable to temperature extremes. They can allow easy starts at low temperatures, yet still give good protection at high speeds and warm temperatures. This is a decided advantage in changeable climate or in long distance touring.
If your engine takes a long time in building up oil pressure after starting in warm weather, when using 10W-30 or 10W-40 oil, the problem can often be solved by switching to 20W-40. This is not specifically recommended by AMC, but it is a proven method.
See Figures 1 and 2