I have my "new" mechanic telling me to NEVER use synth oil in my '98 or '03 XJ8's engines. I have been doing it for years, maybe I've been lucky...or is this true?
He did an oil change on my '98 and replaced the synth with standard oil (146K miles) and the engine started running "loud"...now I have a loud "ticking" like a valve-type sound and he's telling me the tensioner seals are going bad -and attributes it to using synth oil, bad for the seals, etc....I have never had a code come up on this car, it has run like a dream.
Many thanks in advance

 

You need a new mechanic. I think over 90% of the jag owners are using synthetic oil. Have the tensioners been updated with the metal body type?

 

Have you ever heard of, or experienced engine “noise” after switching from synth to Dino oil? It just seems a bit coincidental that it started after the change.

 

anything is better then factory fill. all 5w30 dino oil these days are blends. supertech 5w30 syn is dirt cheap, run 10k miles with a good filter and you’re set


ticking could be a number of things i’d post a video

 

Thank you. Will post video tomorrow

 

I'm currently running Pennzoil 5W30 Platinum Full Synthetic @ about 4,500 miles in w/ no complaints. In fact my car's running @ it's best since my tenure.

 

Thank you King..so no concerns with the seals or anything like that with the thinner synth...? That was my guys concern and experience.

 

Negative on any kind of issues. Modern formulas have additives that condition seals.

 

I think it's possible that if you have seals or gaskets that are starting to fail then the synthetic oils may find those weak spots sooner than conventional oil and create a leak. If your seals are all good then I don't think it matters. I certainly don't think synthetic oils cause seals to deteriorate faster. They may show the leak sooner but i don't think the synthetic oil itself "causes" any seal issues.

I've had several Jaguars and have always used synthetic oil. The only leaks I battled thus far have been cam cover gaskets which luckily are pretty easy to replace.

 

Great to know. Thank you again King

 

That makes sense, maybe because the one is a ‘98 he felt the seals may be a bit worn, thus advising against the synth. Many thanks

 

There is another, more realistic concern, on switching from conventional to synthetic oil. Especially on older engines. The older an engine the more likely it is to have some deposits settled around the crankcase and other places. Your oil picks up dirt, combustion bits etc. Most of that will end up in your filter, some of it is kept afloat in the oil itself. But over the years many parts might get covered with an almost permanent layer of dirt. If you start using synthetic oil on such an engine, it is likely to soften up those stuck bits and they end up in the synthetic oil moving about, blocking maybe oil channel, fouling up your filter quickly etc.

So if in any doubt, for peace of mind, after replacing a regular mineral oil for a synthetic one, don’t wait too long for the first oil and filter change.

Jeroen

 

Thank you Jeroen, that may very well be my issue. When I bought the car, it was without records, so I don’t know what type of oil was in it. I immediately did an oil change and went to synthetic...I’ve been through two synthetic oil changes since, and now moved back yo regular oil at the behest of my mechanic. Maybe I should do another change since it’s only been a couple of hundred miles, and see if that clears up the noise I am getting from the engine. I believe it is related to this change from synthetic to regular oil, may some bits have come loose and it needs a flush.

 

Did the noise appear immediately after the swich to mineral?
Does your engine have VVT? It has if it is 3.2 Lit. VVT-s are known to make noise with poorer quality oils. What brand mineral oil is now in the engine and what grade?

If the noise started as soon as you got the mineral oil in, and you did not have it with synthetic, the logic is to go back to same synthetic and not to try with another fill of the same mineral.

 

Yes, the noise started almost immediately after the switch to mineral oil. It is a 4.0L V8 XJ8 engine, so the VVT doesn't come into play (I think...). Still, I am being told that with an engine of this age (1998) with 145K miles, the synthetic is too thin, especially if there are seal issues I am unaware of. Do you still recommend a switch back to synthetic? His concern is the seals around the lower timing tensioners.

 

It is a VVT engine, the first gen two stage type.

 

That synthetic oil is "too thin" is a nonsense. How thin or thick the oil is does not depend on whether it is mineral or synthetic but on what viscosity grade it is (0w-20, 0w-30, 5w-30, 10w-30, 10w-40 etc., thinner to thicker). And synthetic oils generally hold their viscosity better than mineral at temperatures and with age so, if a meaningless general description "thick" or "thin" is to be used, then I would say that synthetic is thicker.

As pointed by "xalty", it has a VVT so the noise you have could be coming from there. For the 1998 Jaguar engine, 10w-30 or 10w-40 oils are recommended. At the mileage that you have, I would go for 10w-40. I only use fully synthetic oils in all of my cars, including my 1999 Super V8 (no VVT).

As to your mechanic's concern about the "seals around the lower timing tensioners", there are no rubber seals there.

 

My 1998 XJ8 - been using synth for these 22 years - never had an engine problem

 

May I ask what grade and brand? Thank you

 

it could be the brand of oil causing noise, I had a motorcycle that I always used pennzoil and switched to castrol on one oil change, the bikes clutch started slipping going up hills and grabbing at stops. changed the oil back and no more problems.
I also have an uncle who used one brand of oil and when he took it to the dealer they put in some other brand, the vehicle started to run rough and smoke, he changed back to his brand and it also cleared up.
I guess all oils aren't the same.. just change back to what you were using and hopefully the problem will clear up.
I have 2 xjr's one a 99 the other an 02 both use syn oil not problems.