Quite amusing to read this debate about changing oil!! it's striking to see that most of the enthusiasts are concerned about motor oil viscosity and brand, just like me!
But I have faith in what Mitsubishi specifies as motor oil change intervals and oil viscosity..
Concerning 5w20 grade motor oils, I suppose the manual does also specify the specifications that have to be met like ACEA: A1 or B1 and the min. API spec (example for Mobil1: SM, SL,SJ,EC,CF,CD).
I think these values express the thermal and oxidation stability, so these figures are quite important to verify.

I can only think of 1 reason why car makers advise using low-viscosity grades in the newest models: fuel economy. I suppose the mivec V6 doesn't get extremely hot then?
On the contrary I wouldn't dare using semi-synthetic 5w20 blends because of its inferiour viscosity stability on the long run.
I'm confident a 5w30 will never hurt, and will naturally provide even better protection in ultra high temperature conditions.

 

I wonder what mitsu would have to say about using 5w30, would it void the powertrain warranti?? I live in florida, so does that mean I should not be using 5w20?

 

ya know, the funny thing is this, if you change your oil every 3000 to 4000 miles, then any good motor oil of the proper weight (conventional, synthetic blends, or full synthetic) should be more than fine.
You are not putting that much time, and wear on the motor. If you look at any, and I do mean any other motor, they go buy hours of use. Take for instance a new bobcat, it should go between250 to 500 hrs between oil and filter changes. If you figure that you drove 60mph (just for ease of use), it would take you 60 minutes to cover 60 miles. Duh right, But, figure out how many miles you would drive in 250 hours, (simple really, if your covering 60 miles in one hour, then multiply that 60, by the 250 hrs) and you get15,000 miles. not even close to a motor that isnt built as well, and does alot more work. Hmmmm sound strange. Figure it this way, the bobcat that sits in our garage, weighs 9000lbs, give or take. subtract that from the 3800lbs the outlander weighs, and you get5200lbs diffrence. I know, I know. The mitsu makes 220hp, the bobcat makes 85. Figure that for every 1hp the mitsu has, it has to carry 17.27lbs, and the bobcat has to carry 105lbs. Now things start getting interesting. I know what you are all thinking, but the bobcat only one gear.
I guess what I am saying in all of this is that the poorly built motors in bobcats (not that there really all that bad, there just designed for another purpose, and therefore dont have to be built that tight, no emission regulations you know) and if they can go that long between oil changes, in much worse conditions then 3-4000 miles on any good oil is just fine.

Oh, and before anyone starts, let me also say that they are diesels, and therefore the dont rev that high. But figure2500k rpms in a diesel that redlines at 3200 is like 5500 when you redline at 6200.