I've only changed the oil twice in the last 50,000 miles, but that's because it was burning so much I could simply add a quart every 2 weeks. That stopped when I changed to 10w30. Now it uses a quart every 6 months.

 

I guess changing oil is cheaper than fixing the valve seals.

 

it is if your valve seals ever need to be changed. but if not, doing nothing is cheaper than changing oil when it's not needed.

 

FYI if thicker viscosity stops rapid oil loss it means oil is being burned or leaked..

 

yes, that's the whole problem. Since Chrysler has changed the recommendation from 10w30 to 5w20 (to help fuel economy at the expense of engine life), the 3.3 and 3.8 burn oil. Using a higher viscosity as this engine was designed for will solve that problem.

 

I run $18.00/5qt Pennzoil 5W-30 high mileage and get almost no loss.. I haven't experimented with other vendors outside Mobil1 though. Mostly because of price.

Also at running temperatures 10w-30 and 5w-30 become almost identical viscosity. That's why they have the same specs over 50F. This means the ratings have nothing to do with economy. I suspect the only way to get better economy is with full synthetics that tend to hold properties better against heat and don't move in to thicker warm viscosity rating.

 

that's all well and good, and if it works for you that's cool. But the fact remains that the 3.8 was designed for 10w30 and the reason it was changed was for economy reasons whether that panned out or not, and real world experience has shown me that 10w30 works better than 5w20. If you want to use 5w30 instead as a compromise that might work just as well, but I'll go with what the engine was originally designed for since it works so much better for me than 5w20. Not interested in doing any more experiments since I've found what works great.

 

If it works well for you stick with it.
Personally after some experimenting on a couple cars, there's no advantage to synthetic over conventional for an average car, from what I saw. People will say mileage, the vehicles I tested could not make over 3k before the oil was shot whether it was conventional or synthetic.
I use 10w30 in everything except my high-comp built motor (which gets 5w20), it's never failed me.