Going backwards, synthetic to conventional.

[Torrid]

So when I first got the Jaguar at 75k miles I changed the oil to Mobil 1 0w-40 and it immediately started leaking like a sieve, multiple spots. I'm sure it was running conventional all its life, the good old myth of switching to synthetic causes leaks that I never believed. Halfway into the OCI all oil leaks completely stopped. Switched to Edge 5w-30 and everything stayed dry. I just switched to PYB 10w-30 and now it's leaking profusely 1-2 weeks after the oil change from the right bank cam position sensor seal, which was the spot leaking the worst when I first went synthetic. It's bad enough it left a silver dollar sized spot on the garage floor overnight. It's obvious I need to source this seal and replace it, but it seems like an odd chain of circumstances.

Yes it's a failing seal, but why would switching to synthetic and then back to conventional be when it shows itself?

 

[SwampSurvivor]

Nope. The synthetic oil ate up whatever crud was stopping the engine from leaking. PYB is also a great cleaning oil, so that also helped clean up more crud!

 

[Lolvoguy]

That's a very new vehicle (IMO) to be leaking that much oil.

THanks for the post. I dont' feel so bad anymore about my old BMW leaks

 

[Torrid]

Originally Posted By: Miller88
Nope. The synthetic oil ate up whatever crud was stopping the engine from leaking. PYB is also a great cleaning oil, so that also helped clean up more crud!



That would make sense to me if it was leaking the whole time after it started, but it didn't. I guess the old saying is true, if it's not leaking it's not a Jaguar.

Yeah it's relatively young car still. The interior is still immaculate. It's needed some TLC mechanically. I'd just like to make it a month without turning a wrench on it.

 

[rideahorse]

So what were you trying to gain by running a high priced synthetic oil that dino oil was not already doing with no problems.

 

[Bottom_Feeder]

Originally Posted By: Lolvoguy
That's a very new vehicle (IMO) to be leaking that much oil.

It's a Jaguar. It's probably been leaking oil since the day it left the dealer.

 

[Torrid]

I had it sitting around from my GTO I had. Between 0w-40 and 5w-30 I must have had 20 quarts of oil. The GTO obviously was driven harder and had a much smaller sump and a larger motor. The Jaguar doesn't need it, but I wasn't going to not use it.

 

[LeakySeals]

When you switch back to conventional and the leak suddenly stops you will have an answer. I'm thinking it was a crud clean up plugging an existing hole so going back will make little if any difference it's still going to leak. Maybe less cuz the flow is not as good but it's still will leak. Let us know

 

[LeakySeals]

You could try running Mobil 1 high mileage 5W30 for a while. it's worked good stopping leaks for me. And you get the benefit of a synthetic oil so you can leave it in twice as long. Takes a while to puff the seals up though. Usually the second oil change you start seeing results results

 

[Torrid]

Originally Posted By: LeakySeals
When you switch back to conventional and the leak suddenly stops you will have an answer. I'm thinking it was a crud clean up plugging an existing hole so going back will make little if any difference it's still going to leak. Maybe less cuz the flow is not as good but it's still will leak. Let us know


I am running conventional. That's when the leak started again. Anyway the seal is only pressure fit. I was able to pop it out with a flat screwdriver. The dealer has the replacement for only $30 and I'll pick one up today. It's my only leak and with as simple as it is, literally a 30 second job so I can't complain. The other side is spotless so I won't bother with replacing the left bank seal. Seems to be a common failure point, but it's only an oil splash point and not under pressure.

 

[4wheeldog]

Synthetics clean, which is what most likely exposed your leak. But they also have more seal conditioner than most conventional oils, which would account for why the leaks stopped halfway in the OCI.

Personally, I would continue to run synthetic, probably the 0W/40 Mobil 1, after you change the known bad seal.

 

[Torrid]

There's really no reason to run synthetic in this car it doesn't call for it and it has a 7.5 qt sump and I only put 8k miles on it a year.

 

[TheOnlySarge]

Just food for thought....2006 Jag has the oil pump w/high pressure valve. Two O Rings...they get "clogged" or "dirty" and your oil pressure goes to nothing. Gotta replace the oil pump then.
I would be aware of that when making my oil detergent capabilities decisions.
I'm still thrashing my GTO

 

[Torrid]

Originally Posted By: TheOnlySarge
Just food for thought....2006 Jag has the oil pump w/high pressure valve. Two O Rings...they get "clogged" or "dirty" and your oil pressure goes to nothing. Gotta replace the oil pump then.
I would be aware of that when making my oil detergent capabilities decisions.
I'm still thrashing my GTO

I've never heard of that and as a member of Jaguar Forums I can't recall a single 4.2 failure. 4.0l engines had timing chain issues with the early models. Oh and where is this idea that conventional = sludge? I'd expect that elsewhere but not here. I could see that being a concern if this car required synthetic and it was a high strain motor, but the 4.2 has been known to be easy on oil with such a large sump.

 

[dparm]

Modern conventional oils contain some synthetic basestocks anyway. 20 years ago the difference was significant, but with newer, stricter API requirements, the gap has narrowed.

Not sure what that car is spec'd for so I'm hesitant to make a recommendation.

 

[Torrid]

It only calls for an API certified 5w-30 for 10k mile 12 month intervals. It also approves the use of 5w-40 which would be a synthetic, but most dealers didn't use synthetic until the new 5w-20 Jaguar spec was created. I wouldn't mind using that if I could even get it without going to a dealer, but Jaguar never back specc'd lighter oil grades like other makes so I won't try it.

 

[Torrid]

Seal already replaced. Still find the conventional to syn and back to be odd.