Mobile one 5w30 full synthetic will keep you out of any trouble. I have used it since I bought my 2002 new. 7 qts makes it a little pricey but it is a good oil! I go 5 or 6 months or 5,000 miles. I think with the 7 qt capacity the engine is much easier on the oil than lets say my high output turbo saab which is very hard on oil and prone to sludge if you don't use full synthetic and change every 3,000. The TB's 4.2 is a very well designed engine.
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