Did the Rotella and still have this high pitched ting- again only on acceleration in drive/reverse. Not that apparent if at all while reving in neutral or park.

 

It is best that you record or video tape the sound and let us review and comment on it.

 

Mobil 1 synth is designed for and better suited to high performance OHC engines. I have used it for years in both Vauxhall 2.0L 16V race engines and 2.0L Ford Cosworth engines running at c10,000+ rpm on roller body injection with individual spark coils and it performed well once hot but I would guess not really suited to truck tech engines. On road vehicles I use semi synth even on diesels which the Rover V8 is equivalent to in low tech technology.

 

Why do people insist that Synthetic oil is good for these engines?
I would put in a good 20W/50 for the summer - or what remains of it -
non synthetic.
And get it out in 3000 miles and do it again.

Synthetic too thin.
The tolerances in these engines are too wide.

 

First, I agree with OffroadFrance that one of problems common to these engines is valvletrain wear because modern oils are not designed for use with flat tappet camshafts. The additive package in a diesel oil is appropriate for the design of this engine. And almost all diesel oils are 40w, so they're the only game in town.

Second, most engine wear happens when you crank a cold engine and the thick ambient temp oil tries to lubricate the engine. Until the engine is warm, it's not flowing well enough to thoroughly lubricate. So, a 5w-40 is designed to flow more freely when cold, but then stay thick enough to be an effective lubricant when hot. In this day and age, 15w or 20w oil are outdated technology that induce additional bearing and valvetrain wear every time you start your truck.

And about changing your oil at 3000 miles, I had an analysis done of my last oil change (running M1 TDT 5w-40), which was at 6000 miles, and it could have been run for a few thousand more miles according to the lab. I don't plan run my oil that long, but the 3000 mile oil change is overkill if you run a quality oil.

 

I think I've forced my find- It's feeling like its coming at the connection of the exhaust and exhaust manifold. It looks like there was a weld done there at one point which has probably now come undone.

Any clue why it originally only making noise while in gear? It's a straight put put put from that area now- in all gears and park while revving the engine.

 

I think I've forced my find- It's feeling like its coming at the connection of the exhaust and exhaust manifold. It looks like there was a weld done there at one point which has probably now come undone.

Any clue why it originally only making noise while in gear? It's a straight put put put from that area now- in all gears and park while revving the engine.

 

That's exhaust for sure.
May be head gasket.
May be exhaust manifold.

When you go into gear, there is torque on the engine and the engine
may turn a fraction of a degree in relation to the Y pipe.
This may provide torque on the manifold and exposes the leaking area.

In case this is a head gasket problem - I would stop driving it.
Head gasket problem will force hot gas to cut a slot through the head and or block.

 

X1. The engine doesn't sound rough apart from when the phut, phut noise starts and I reckon that is exhaust manifold or it's gasket. It could be another part of the exhaust somewhere close to there.

It may be head gasket but it's hard to hear this although no apparent misfire however it's not under acceleration or load. I would have it checked over at a good reliable LR garage/shop and have another opinion on it.

 

cover the exhaust with a rag and listen for leaks underneath