I've read Rotella T6 is the oil of choice for the Disco. I just looked it up and see it's synthetic. That threw a big red flag for me.

I'm 45 years old and have never used synthetic because of two reasons: 1) I never had a car come with it in it new. 2) In the past I was told NEVER put synthetic in an older car because the oil seals were not made for it and it will leak like a sieve. In other words, only use synthetic in cars that came with it from the factory, or recent year cars with seals made for synthetic.

Now, let's say I buy a 2 year old car made for synthetic, sure I'd do it. Ask me about my 2002 Disco and I would surely think this is an "older" truck with seals designed for old school oil and not synthetic.

Obviously people are using synthetic in these "older" trucks so please educate me.

Thanks!

 

I have been using the T5 and not synthetic. I have used synthetic, but only in my new Duramax engines, since they were new. 07 has 245000 and has only seen Schaeffers full synthetic. I put synthetic in an older chevy engine and yes it started leaking from several places. Hence I will not in my Disco. If the time ever comes where I totally rebuild this engine, I will more than likely install the dual-bypass filter system and run the same Schaeffers full synthetic.

 

I think I'll look for something like the Rotella dino oil. I found some threads on the subject and opinions are all over the map. I'm in Texas so no super cold weather here.

 

Seals in your D2 were mfg'ed after the advent of syn oil and there are no known compatibility issues. Many of the earlier reported issues you mentioned resulted from engines having marginal seals to begin with. I've used both in new and older engines with no problems.

Syn is supposed to have the advantage of extending oil change intervals. If used for that purpose it may offer an advantage. If in doubt Rotella and others have fine non-syn oils in a wider choice of weights.
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Ok, great to know. I wasn't sure if people used synth because the engine performed better or just more mileage.

Anyone know if synth is used and leaks start, does switching back stop the leaks or is the damage done?

I'm leaning towards the Rotella T-5 10w-40.

I did not realize how hot a topic this was. I was reading threads I just found and folks go nuts on this. Sorry.

 

Yes it does. All I will currently profess to knowing is the API spec indicates that 10w-?? is good unless seeing local temps below 0 F and that in the US year-round use of lighter weight oils is recommended to boost the mfgs. mileage ratings a smidgen.
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I can attest that the T6 will leak more than standard Dino. I've also tried T5 as well as standard 15w40 Rotella. Of the three in your climate, I'd go with the 15w40. I've used it year around here in VA in as low as negative 12 degrees last year with no issues. I'm currently running a mix of T5 and Pennzoil 5w30 Dino with a bottle of zinc additive and that's also working pretty well, but will run you more than the Rotella. I'm only running it because I already had it in the garage.

Also be sure to get a larger high quality oil filter. The Mobil 1 M1-301 is my primary choice, but the Wix 51515 and 51515XP are also decent. Just not quite as good, but also a bit cheaper.

 

Folks go nuts on the 15w40, not the thin or synthetic types of Rotella.

These are old school engines with old castings used in mfg. Thinner than 15w oils in most of these engines unless it is below zero are not optimum generally resulting in louder ticking and rougher idle. I would assume due to a lower oil pressure but i've not personally measured that.

The dino Rotella with high zddp is what you want... My second choice would be swepco 20w50... speaking from my own observations putting 140k miles on my truck and trying many different options.

 

My oil of choice for years since shortly after being introduced by Castrol. No issues even when living as far north as DC area unless subzero temps with a weak battery. When the heat's on as it often is on with LR engines a higher viscosity oil is a plus. Mobil 1 15w-50 is sold at at my Walmart and would've been used for may last change if current supply of some syn 20w-50 hadn't been in my oil cabinet.
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Thanks for all the good info. I see your points, also the different weights of oil. I do already use a Wix filter but will switch to a high capacity Wix or Mobile 1 filter. I'll likely start with a Rotella T 15w-40 and take it from there. As things heat up I may go up to the 50w oils and higher viscosity.

Thanks again. Great info.