Sorry for yet another "which oil do I use" question...but, I can't find the right answer for my application.

Live in Washington state and temps can get to ZERO sometimes during winter. Doing Head gaskets, water pump, oil pump, etc tomorrow. Heads were just completely done too. 99 d2 with 129,000 miles and need to know which Rotella to use and which weight given my geographical location, mileage, and services being performed at same time. Walmart has rotella t6 in 5w40 or Rotella t 15w40??

 

5w40 for the upcoming winter; 15w40 for the summer. or just pick one and stick with it. There's numerous debates on the interweb forums.
http://www.dieselplace.com/forum/sho...d.php?t=430746
http://www.dieselbombers.com/dodge-t...0-vs-5w40.html

They both have the same viscosity at operating temp (40), but the 5 will be lower in viscosity when its really cold outside than the 15.

 

I think the other difference is the t6 is synthetic. Should I be usin synthetic now?

 

meh, synthetic/conventional isn't as big a deal as some people make it to be. if you change it regularly and use a good filter, you're already giving yourself a very good chance at long engine life (all else equal). using synthetic might increase your odds a few percent, quiet down some interal parts, etc. I always switched to synthetic oil after I got past 100k miles in my vehicles and never had a problem. I'm sure I could have been just as fine using conventional.

whatever you use, change it regularly and your engine will thank you.

 

Here is my thought synthetic oil was not even a thought 50 years ago when they built this motor why use it now? This is not a high performance motor this is a snail.

 

It my be a old snail but syn oils have better additives ,run cooler ,and last longer,help to cleen your motor. Sounds like a cheep upgrade to me. Just saying. Good luck blamo.

 

15w-40 shell rottella diesel oil. I concidered synthetic oil for a while then when I was changing all my fuilds I noticed a trend. Land Rover used synthetic fuilds just about everywhere on a Discovery II except the engine. Seeing they are the one who have to
warrantee all these truck I have to figure they had a reason. JMHO

 

I'm located in Philly and the temps get fairly cold here as well. Last year I ran T-6 all year long. I switched over to 15-40 beginning of this year and plan to run w/ it throughout the winter. If the truck gives me problems starting in the cold weather, I'll drop the 15-40 and replace w/ T-6. She is soo much quieter w/ 15-40. And its cheaper. Another deciding factor, someone already pointed out, I change my oil and filter every ~3k miles. Its cheap so why not

Each one of our engines are unique in their own special way. Find what suites your vehicle and stickw/ it.
Just my two cents.

 

I'm in New England and ran 15w-40 all year,it was a mild winter.
I dont know how good an idea it is to switch back and forth from conv.oil and synthetic, they used warn you against that. They would say dont do it pick one, and stay with it, but that may have changed.

 

I had always been under the impression that you were stick with synthetic once you switched to it?? Not sure where/why I heard that but it's been in the back of my peabrain for years now.

I looked throught the history of receipts and it appears the last oil change the previous owner used Valvoline max life 10w/40, which is a semi-synthetic. Prior to that it appears the original owner had been using Pennzoil Platinum 5w/40, a full synthetic. I am leaning towards running the Rotella T6 5w/40 synthetic after i put the motor back together today.

I guess my question at this point is this: Is there a reason I shouldnt run 5w/40 synthetic at 129,000 miles and new top end gaskets??