I been reading alot recently about the benefits of using a dual diesel/gas rated oil in older engines and I'm thinking that one of oils mentioned in the thread title might be an improvement over the conventional SN rated 10W/40 oil that I'm currently using. The higher zinc content and perhaps superior cleanability of the Rotella are two benefits that I see.

Opinions welcome please.

 

Does the engine have roller or flat tappets? (excuse my ignorance)

 

I don't know. How's that for ignorance? Perhaps others will know.

 

I've been on T6 since Apr, 2011 @ 80k miles, now sitting somewhere beyond 112K, very happy. Car was on 15w-40 of unknown brand when I bought it at 63k, I tried Valvoline 10w-30 synpower, then 20w-50 VR1 Racing oil, before getting the gouge from Motorcarman and Brutal to use the dual-spec diesel oils.
The 10w-30 went through it too fast...had to add a couple of quarts for makeup oil in 5k. Did avg 20.7 mpg on it though. Mileage dropped off to 19.9 with the 20W-50. Getting 20.4 on the T6. Caution those avg's are over roughly 5k, 5k, and 30k miles, respectively. Also, essentially "winter" vs. year-round on the 5w-40.

Nice commonization with my diesel Excursion, too - but with 15 qts for it, and 9 for the X300....sure seem to buy a lot of gallan jugs of it!

 

I use the 15W40 Rotella or Dello in my 1992 XJ6. I also have a 1982 VW Rabbit Diesel (shop parts chaser) and use it in that also.

The Jaguar dealer I worked at used Mobil 15W40 (bulk oil) in ALL JAGUARS until 2006 when I left (a throwback to the old days). I heard they switched to 5W something or other sometime after I left. We advised that the newer cars did not need the heavier oil but management does what it does.

bob gauff

 

Shell Rotella 15W40 in a AJ27 V8 over here, which is actually a step back from Castrol 20W50 year round in all previous vehicles.

 

On my last oil change , we switched to Castrol 15W40 , neither too thin nor too thick to these engines

 

The Castrol Hypuron or Castrol Tection?

 

Anybody know the answer to Mikey's question? Engine is the AJ16 4.0 in a 1995 XJ6.

 

Castrol GTX

 

I just checked the official service manual. The tappets are "flat", no rollers. so that leads into the question of ZDDP (Zinc phosphate for anti-scuff) in the motor oil. The ZDDP in motor oils was phased out in the early 2000s to make the federally mandated 150k mile life of catalytic converters a possibility. It is now widely believed that the removal of ZDDP has lead to failure of the tappets & camshafts in many early flat tappet cars. The Rotella & other diesel & racing oils still have ZDDP but some say not as much as they used to. This leads me to ask:
-Has anyone here burned-up their camshafts & tappets this century?
-Has anyone here needed to replace their catalytic converters when using off the shelf automotive (not diesel or racing) oils ?
-Has anyone who in using the oil with ZDDP needed to replace their cats?

If no-one has had camshaft or tappet problems maybe we can go with the newer oils & hopefully extend the life of our cats.
I'm running Rotella T6.

 

Flat tappet versus roller tappet is not really germane in the discussion of the Jaguar six because it is a DOHC design utilising cam buckets. The loads are therefore lighter but it is still a wiping load.

BTW, ZDDP is benefical to more than flat tappet cams. It addresses any situation where you get into boundary lubrication.

The T-6, if you can find the specs, is likely to still have somewhat elevated levels of ZDDP. This is because it is primarily marketed as a diesel HDO, and with a weight over 30, it gets a regulatory break on the ZDDP levels. Nevertheless, it is still also marketed as meeting API SJ for spark engines.

One really attractive factor in considering HD diesel motor oils is that they are marketed to fleets where engine wear is carefully scrutinized. Unlike the raw unwashed public, fleet managers *do* get access to the detailed technical data. They also participate in used oil analysis programmes. This is also mirrored by the diesel engine manufacturers such as Caterpillar, Allison, Mercedes, Volvo and Cummins. It would be reasonable to believe that if a particular oil is good enough for them, it's a good oil period. BTW, not all such oils are dual rated for both compression and spark engines. The information is on the label.

 

Thanks for the background info and I look forward to seeing input from owners of the affected cars. My other car (non-Jag) has a conventional style OHV V8 with flat tappet lifters. The reduced levels of ZDDP in modern oils is a genuine concern, possibly not applicable to the same extent to the AJ16 engine series.

 

Thanks, Mikey, for steering this in the direction of how dual-spec diesel oils can, with their increased zinc content, be beneficial to flat tappet engines.

Thanks, n_sweeney, for verifying that the X300s do have flat tappets.

I think I'll switch to the T6 5W/40 as a year-round solution here in Florida.

Regards,
Joe

 

I guess what I'm most interested to know is: Do we really need to use the oils with ZDDP. Our cars, having DOHC have lighter valve gear & proportionally lighter valve springs than the old pushrod engines did. If we can run them reliably on oils without ZDDP we might realize longer catalytic converter life.
That is why I asked if anyone has burned-up their valvetrain this century. If it never happens then maybe we can do without the ZDDP.

 

It's been discussed at length, and ZDDP is a pretty unique search term that should bring up those threads for you.

 

Well, today my roughly 5k miles on the Pennzoil conventional 10w40 was up and I dropped it and replaced it with Rotella T5 10w30 which is a thick 30 weight, SM rated oil with a good dose of ZDDP. I considered the T6 but since my owner's manual recommends 10w30 I thought I'd give it a shot, but only after researching that the T5 is a thick 30 weight. We'll see how she likes it.

 

I've used Mobil Delvac 1 5W-40 previously in my car sucessfully.

 

Not one person has qualified their choice of oil to their environment / season. ... oil choice can't be generalized.

 

At some point, the reader has to rely on their own intelligence to realise that all such threads are only data points to consider in light of their own circumstances.