Oil for 4.6L Flat Tappet?

[Peted]

This is my first question on the forum. I would like some input.

I have a Land Rover Discovery II with a 4.6L flat tappet motor, 60K miles. I do city/hwy driving (I want to say I put on 8-10K miles per year) as well as some four wheeling on the trails. I live in south Florida and it is getting hotter, around high 80s soon to be low 90s.

I have used RP 15w40 a few times and my last oil was Rotella T Synthetic 5w40 for 4500 miles. I was planning on taking a used oil analysis of the RTS but I had an oil leak and had it fixed under warranty. I was dumb and did not think about taking the sample before the fix and the dealer had to replace the oil pan gasket and refill with Valvoline conventional 5w30. Though, it could be their synthetic. Last time I asked the dealer they said they use conventional.

As far as I know that oil is not going to protect my engine in 90* heat out on the trails. Valvoline's website does not even list the HTHS. It is what the dealer stocks for all the Range Rovers and fancy LR3's. My manual even states to use a 5w40 or 10w40 depending on location and temperature ect.

So I am going to change my oil. Right now it is between RP 10w40 or a couple AMSoil oils: 10w40 AMO, 5w40 AFL, or 5w40 DEO. Or go back to Rotella T Synthetic 5w40. I Will be taking a used oil analysis of what ever oil I use around 4500-5000 miles. In the Land Rover world it is said that these motors run Very rich and Everyone changes their oil every 3000 miles regardless of what oil they put in.

I also heard Mobil Delvac could be a "better" oil than RTS simply because it is believed Delvac uses a higher percentage of PAO or what not. So add Mobil Delvac to that list.

I will be using a RP oil filter.

I really wanted to see what the Rotella T Synthetic 5w40 used oil analysis entailed but oh well.


Thank You.

 

[addyguy]

Of all the oils you listed, my pick would be the AMO 10W-40. Very solid oil, with the protection your flat-tappet engine needs.

 

[Peted]

That is what I'm leaning towards the most. I just couldn't find any used oil analysis or any information on it through the search. I searched back a few years and nothing.

 

[Rob_Roy]

Just curious, why did you discontinue use of the RP 15w40?

At the end of the day, I think any of the oils you listed would do a fine job. My personal preference would be a conventional 15w40 due to the short drain intervals, fuel dilution, and lack of cold starting. Something like Delo or Delvac 15w40 and would offer plenty of protection and not empty your wallet.

 

[Peted]

Originally Posted By: Rob_Roy
Just curious, why did you discontinue use of the RP 15w40?

At the end of the day, I think any of the oils you listed would do a fine job. My personal preference would be a conventional 15w40 due to the short drain intervals, fuel dilution, and lack of cold starting. Something like Delo or Delvac 15w40 and would offer plenty of protection and not empty your wallet.

They stopped carrying it at the local auto parts stores.

 

[daman]

Mobil 1 Turbo Diesel Truck or Mobil Delvac 1 will work..

 

[bmwtechguy]

I'll vote for the conventional Delvac or Delo as well for 4500 miles. You just don't the 5W-40 there where you are and the HDEO will protect your flat tappets fine. For synthetic, I like the AMO for the same reasons stated above. I think that oil should go 10k miles without trouble, unless your UOA indicates severe fuel dilution.

 

[wannafbody]

For flat tappets use an oil with high moly, and ZDDP. Schaeffers is another choice.

 

[Peted]

Thanks for the input!

Anyone know where I can find some Amsoil oil? I can't find it online besides their website. My local speed shop does not stock it.

 

[daman]

there going to say site sponsers here...

 

[UNC017]

I agree with those who have said any of the oils you mentioned should do fine. I've been getting good results with RTS and probably would pick it personally. The more I read/learn about the Shell XHVI Group III+ base stock, the more impressed I am.

My opinion is that you really don't need to worry about the fact that its a flat tappet engine. Like my Jeep 4.0, its got a very mild cam and gentle valve springs- its built for torque, not screaming at 7000 RPM. Plus at 60k miles its fully broken in. If you choose to run a non-HDEO SM oil it would probably do just great.

Oh, and

 

[Georgiadave]

I would use German Castrol 0-30. It is an SL oil with lots of ZDDP, and is readily available. Read the GC sticky for more information.

 

[mechtech2]

What is the problem with flat tappets? Especially after break in?
By far, most vehicles have them.
And, they use conventional oil with no problems.

Racing engines or high performance is another thing.

 

[UNC017]

Originally Posted By: mechtech2
What is the problem with flat tappets? Especially after break in?
By far, most vehicles have them.
And, they use conventional oil with no problems.

Racing engines or high performance is another thing.


Actually, relatively few engines made since the mid 1980s have flat tappets. Far and away most have roller lifters, which have a completely different wear dynamic. There are notable exceptions- the Jeep 4.0 was flat tappet until the end of its production run. A few import engines remained flat-tappet until recently.

But you're right, its mostly a problem with higher spring pressures than recent flat-tappet engines use, and its far less of a problem after break-in than it is early in an engine's life.