the 15W40 is my beverage of choice - and cheap enough to change often.

I'm afraid mine will never purr thanks to a horsey-sounding pulley somewhere (been that way since new in 2000).

Completely agree! Plus its about 3 dollars cheaper than even the Base Exchange brand oil. I love it for Hawaii's weather, however when I was living in Connecticut with my D1, I ran 10w30 and didn't have any issues, but I also didn't know any better.

I've ran it with 20w50 that I had left over from the RX7, but I felt that the 15w40 was better suited for the Discovery.

10W30 OK under 95 F. But where I live that is just a few months of the year. That 40 portion is good for a worn engine like most of our aged Discos.

Switching from Castrol 10W30 to Rotella 15W40, we'll see how the engine performs. It's getting hotter here in Vegas so I'm sure it will make a difference. BTW is a Motorcraft FL1A a good filter to use? Wally World stocks them for dirt cheap and had some good results with them in the past.

Just my 2 cents...
 

I run the Rotella 15/40 from May through Oct. Then switch to Rotella Synthetic 5w40 for the winter. Its worth it and it can be found anywhere for pretty cheap. Even walmart stocks it and its usually 16/17 bucks a gallon here (synthetic is more), sometimes cheaper if there is a sale. Haven't found a better oil for this truck, I ran it in my 03 for the two years I had it as well.

I've used the motorcade filter. As I said above I have generally just bought whatever filter was available when I wanted to do a change, and Walmart is always open. But check Savannah's post above with a link to filter comparisons. They are not all created equal.

I have been running the 15-40 for the last 2-1/2 years year round. The winters have not gotten anywhere cold enough for me to worry about the weight giving me a hard time. I have been thinking about going to 20-50 for the summer. Doing the slow grind high traffic low speed grind in the city can be brutal. hell last weekend it took me close to 3 hours to go 26 miles. when it gets 98 outside and high humidity I am thinking that the extra weight may not hurt.