Originally Posted By: HawkeyeScott
My wife drives a 2007 Chrysler Pacifica. It's the 4.0 V6 that takes 10W-30 in an age when seemingly more and more cars call for thinner oils. So what does that say about this engine? Does it have to do with operating temperatures? And is it like my 4.0 Jeep that calls for 10W-30 but seems to do just fine on 5W-30? (I won't be deviating for warranty purposes...just wondering.)
It seems sort of unique that a vehicle built in 2007 calls for 10W-30. (Don't get me wrong, I like it. Both vehicles take the same oil and same filter. Kind of nice.)
Also, anyone have a 4.0 V6? What's been your experience? At 36K, ours has been fine. Knock on wood...
This is somewhat a relic from older, lesser quality days of motor oil.
5W-30 and 10W-30 are supposed to be identical in high temperatures (in theory) and 5W-30 is supposed to protect the engine better in low temperatures and have better fuel efficiency, which helps to protect the engine even more. But in reality since 5W-30 contains more viscosity modifiers (VIIs), it's more likely to fail under high temperature and/or high load (high shear) and/or over time when the oil deteriorates. This is the reason why some car manufacturers recommended 10W-30 instead of 5W-30 in the past -- large amount of VIIs used in 5W-30.
But nowadays quality of oils have improved. We have a new specification: ILSAC GF-5. If you buy an ILSAC GF-5 fully synthetic 5W-30 oil, it will have minimal amount of VIIs (too much VIIs is the reason why some manufacturers recommended 10W-30 instead of 5W-30) and it will perform as well as 10W-30 in high temperatures, high load, and extended oil-drain intervals.
So, the answer in short is: Use a good-quality fully synthetic 5W-30. I recommend Pennzoil Platinum Full Synthetic GF-5 5W-30, which became available recently (in GF-5 quality). Other full-synthetic GF-5 5W-30 oils should be available soon. Also, make sure that the bottle has the API starburst symbol in the front, even if it's fully synthetic.