good old bob the oil guy

 

I completely agree with your sentiment, but there's one important caveat. Our trucks have flat tappet cams, and need a oil specifically designed to reduce cam wear. That is why we recommend diesel truck oil - it always has higher levels of ZDDP. Unless you are using an ZDDP additive with your 0w-30, you are inducing top end wear with that oil. Also, less than 40 weight oil isn't recommended by Rover for summer temps unless you live way up north.

 

but, bob the oil guy said:

 

Thanks, Dr. Mordo.

I have just owned my "new" 2003 Discovery II for 1 week and am in the active learning phase. I suppose a reasonable approach would be 0-30 in winter and Rotella 15-40 in summer.

 

You missed an important bit about ZDDP, which 0W-30 does not contain. And the only oil in that grade I have ever seen is Mobil1 which us usually quite expensive. If you're going to pay more might as well go with Shell T6 since it is a year-round solution that flows well in Winter and provides viscosity in Summer.

 

Bingo. That 0w30 will kill your cam in a heartbeat. Trust me, I had to replace mine a few months ago when I did head gaskets because it was starting to wear so much.

 

Or go not as much more and use semi-syn Rotella T5 5W30 in winter and T5 15W40 in the summer.

 

I am running 15w40 year round here in NJ. It has been my experience that it definitely leaks less than lighter oils. The truck does not complain.
~Edit~
The truck complains no matter what oil I run in her. Same tick tick tick sound regardless of lubricant type. Rotella is cheap and anything that keeps less oil in my driveway is a good thing. The amount of rainbow water in front of my house when it rains is a bit embarrassing.

 

I'd run Rotella T6 all year around almost anywhere. Why change back and forth between oil weights? Especially in NJ since 10w40 will only get you down to 18degF and with the winer you guys have had or if you venture north, you need the 5w40. If the 5w40 leaks then fix your oil leak. My 04 is in the shop getting a new rear main seal and oil pan gasket.

 

My truck sounded much worse and ran rougher when I ran Rotella 15w-40. I didn't make it to 3000 miles before I dumped it. When I replaced it with M1 Turbo Diesel Truck 5w-40, it was so smooth it sounded like I had put butter in my engine.

That was my final experiment with non-synthetic oil.