ixne.. it more depends on how many miles you have on your engine. stock 5.0 needs 5 quarts of 10-30. If you are upwards near 100K, run 20-50.
The more miles you have on your car, the more distance there is between the metal contact points in your engine. This calls for a thicker oil. Runnin 20-50 will also help with that pesky rear seal leak
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