Hi everyone, I understand that engine/oil questions are frequently asked and answered on this forum. However, after scoping far and wide here, and throughout the web, I can't find anything that truly relates to the questions I have regarding my own engine and the oil I currently run (DII '04 4.6L V8).

I live in Indiana and currently run M1 synthetic 10W-30 extended performance (lately it's been as cold as -16, but usually isn't this cold regularly). Given the temp, should I be running 5W-40? I so far seem to not have any issues on cold start or driving. Anything I should be concerned about later down the road? Pun not intended!

Now, the real impetus for this posting is that I have developed a VERY slow oil leak. It seems to leak a quart about every month and a half or two. I will post pics of it later, but it seems to have started some time after replacing the water pump and timing cover gaskets about 7-8k miles ago. HOWEVER, I have been running M1 synthetic since August of 2015 (vehicle had 65k on it then, now about 86k) and I didn't have any leaks until now. I don't know what was previously used in the engine.

I have read that running synthetic oil on older vehicles is bad and could cause it to develop leaks, but a 2004 shouldn't be too old, especially when I started using synthetic when it had 65k? My biggest questions are 1. should I be concerned about this very slow oil leak and get it looked at and 2. is the M1 synthetic the suspect? If so, why would it be, and what would be a better alternative? How can I make this engine last for a LONG time as a daily driver...

LR recommends using Castrol of course, and I've seen everyone talk up Rotella. With recent discussions about how they've redesigned Rotella's formula, why keep it in our D2's and why switch?

I know this is a lot but I'd appreciate any help I could get on any of the questions!!!

Thanks for all the help.

 

I would dump the synthetic ASAP and go with Rotella 15w40.

Your engine needs the ZDDP in the Rotella.

Syth will leak where dino won't in these engines.

I'm sure you'll hear more on this topic.

 

I run Redline 5w-40 in Tricky Dick and change every 5k, however, my truck is garaged and the winters in Washington are mild. And, it is not my daily driver.

As far as causing leaks...I have never seen documented proof that synthetic causes a leak but, tons of proof that an existing leak was made worse due to the viscosity of the oil. Meaning, the truck was already leaking and the thick dyno oil couldn't get through the crack.

There is an age where dyno oil is recommended due to tolerance issues. I don't have the exact year but, it is somewhere pre 90s.

Oh...the Redline oil has the zinc additive

 

I heard Rotella's new formula doesn't have as much ZDDP, is this just hearsay and no cause for concern?

Do I need to change the oil filter along with it? If so, any recommendations? Thank you for the info.

 

What filter do you use now?

I use the Mobil m1-301 filter and rotella t6 5w-40. Which I like because both are recomended for use in both my 04 d2 & 94 Land Cruiser.

 

There was a thread on here last year about the new formula, it was concluded that the new formula had enough zddp.

 

I'm using the genuine LR ERR3340 oil filter with Mobil 1 synth 10W-30. I think the wisest thing is to switch to the Rotella 5W 40. Is this a safe bet having had it run on synthetic since 65k miles and with this current filter?

 

Your oil leak is probably from the valve covers. My 04 D2 started to leak from the valve covers around the same mileage you have. I ran synthetic in mine for a brief period: It developed a number of leaks. I have used rotella 15-40 since, and the leak is localized to the valve covers.

 

Here's a bit of where the oil is

 

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