Synthetic Oil Causes Gaskets to Soften, Leading to Oil Leak
 

My new Indy mechanic told me this today!

I find it very hard to believe. I researched & found many articles saying it is a myth.

I’ve used synthetic oil for many years.

This is making me doubt his expertise despite the shops great reputation with Jaguars.

I have a small oil pan leak. I will probably try to DIY following this thread:

https://www.jaguarforums.com/forum/x...ket-xj8-76458/

It may have been true for some cars a long time ago (30 years? 50 years?).

(A bit like some fuel lines can't cope with ethanol but again those are years old.)

If a seal is leaking -- you are going to see a greater leak with synthetic oils because when the surfaces cool and contract the synthetic oil will still be thin enough to sneak by ... conventional oils will have thickened and not leak .. or not as much.

This has been a debate for 40 years -- cars that previously did not leak started to leak and the seals were wet. The seal was not altered -- but it was not capable of holding back the oil -- it't like a kitchen sponge .... pour dish soap on one side and it will eventually come through and drip .... do the same with honey.

Seals -- needed to be improved. different design and material. I use synthetic in most of my old cars w/o any trouble -- including those from the 60's ... the cars that always dripped ... I can't use synthetic. I have an old (02) pathfinder -- that Nissan V6 always leaked with synthetic oils.

You can try using the high mile oils -- they have additives to help eliminate the leaks. That's a whole other topic.

I like using synthetic oil when I have a new car and know the history. For my 99 XJR I use regular oil just because I have no idea how often it was changed or what it was treated to when it was changed before she showed up in my driveway. I think the issue with synthetic isn't that the seals soften but that the synthetic oil does a better job dissolving any sludge or deposits that might be helping to seal something. On a low pressure sealing surface that sludge might be keeping your seal from weeping. I will say that a lot of these rubber seals car companies use these days the rubber can actually dry out. The seals on the timing cover for my beemer 4.4 liter V8 were so dry they felt like hard plastic and came off in pieces. They were weeping pretty good before I replaced them. If the synthetic oil I use for her oil changes keeps those seals soft I'll take it...but I'm expecting they'll just get hard and weep with age like the originals.

I have used synthetics for decades and always will, to include greases. I can run farther on changes (10k-15k), the same if not better mileage and my vehicles are dry. By dry I mean no leaks whatsoever. I took my '97 Expedition (old work truck) to 700k and it was still running when I gave it away. My Corvette has seen nothing but synthetics as has my Jag. I used a syn-blend on the work van (Dodge Caravan).


Oils don't cause leaks, wear and poor maintenance does. Here's article that may help the perspective... ? Comparing Synthetic Oil vs Regular Oil?

A very old myth based on a grain of truth. The first synthetic engine oils (1970's era) contained no seal swell additives. So when a higher mileage car was switched to synthetic oil, the engine seals would shrink slightly (conventional oil naturally causes seals to swell a bit). When this problem was recognized, seal swell additives were added to synthetic oils.

Bottom line, unless you're using 40-year-old motor oil from a cardboard can, synthetic oils will not cause leakage problems from older engine seals.

https://www.bobistheoilguy.com/forum...&Number=530224

That's not exactly correct -- when mobil was doing the research they used conventional oil carriers .. and this continued until I think "V" . And then we get into the question of what's "synthetic".

Mobil actually did a lot of studies on the "leak" situation because it was an issue ... remember most cars used old school 10W-40's some 15w - 50. It was thick. M1 was shockingly thin in the winter when poured into an engine vs what one was used to.

Mobil 1 was only available as a 20 weight oil when it first came out in the 1970's, so that also could have increased leakage in an older car that previously used a much heavier oil.

Mobil 1 had some minor issues when first introduced in the MidWest in the Winter. I had a new Nova 6 cylinder in 76; it leaked slightly at the sump when it got below -15*F. Dealer tightened the pan's bolts, never leaked again. In the insuing forty years, I have never had leaks from Mobil 1 or Valvoline Synthetic (which is what I used in my last 308).

Funny .. can't remember the specifics. Late 1976 my dad acquired a Cadillac for use in NYC office -- they were newly redesigned (downsized) w/ a new 425ci V8. Being in a related business and knowing some of the developers -- the oil was used in the engine. It was originally going to remain for 100k and tested .. but they canceled the tests and it was changed out at 50k. That car sat around idling --- at lot. It bent a valve rod late in life when my brother had it -- I'm sure not oil related. It was sold off still running. I can't say how many quarts the car used in the 50k -- obviously, not the original 5.

If you are having oil leaks it isn't the oil. There are only a few things that will cause an oil leak.
1. Fasteners have loosened.
2. Contamination when installed between the gasket and mating surface.
3. Cracked/warped mounting flanges on covers.
4. Overheating causing gasket failure.
5 Last but the main culprit. Blocked PCV fittings causing high crankcase pressure. It will cause oil pans, cam covers and timing covers to leak.
6. Front and rear main seal leaks is normally due to wear.


When ever I am chasing a leak I always stat with the PCV system and fittings.

This is the original oil pan. 18 years & 88+ miles b4 it started to leak.
Overheating -No, Car has not overheated
Cracked/warped mounting flanges-This would be a manufacturing issue, right. Would not suddenly crack/warp after 18 years?
Contamination-No, oil pan never removed
Blocked PCV fittings—IDK how to check for this issue. maybe?
Bolts loosened-Maybe?
I should buy the small torque wrench b4 I buy a new seal & 1st check the tightness of those bolts! Maybe I just need to tighten some & leak fixed!

The thread I linked in my 1st post had the tightening sequence & the instructions.

Torque is 11-13 nm.

For the cracked/warped flanges, no...not directly after 18 yrs of exposure to road (stones and such kicked up) and weather conditions, no manufacturer can guarantee its parts. Metal fatigues, rubber deteriorates, paint fades...even kept in so called perfect conditions, service is needed. With that, it doesn't defer the possibility of a poorly stamped part, ...it happens, its mass production.

Growing up our MB's and Jaguars leaked -- we had drip pans in all the garage spots. Cars leaked ... MB got a handle on it in the late 70's early 80's ... Jaguar not until Ford took over. keeping an eye on a Jaguar differential was just part of owning one. Cars ... Just don't leak today as they once did .... even in the 70's American cars better .. Japanese cars better still.

Better manufacturing -- tighter tolerances -- better seal material.

To the OP -- My guess if for whatever reason you have a bad seal. If the pan is properly tightened and you are getting a leak it's a case where the thinner synthetic is getting past. The solution would be to replace the seal or go back to regular oil. Remember, when new the X308 was supplied with regular oil and would have been serviced by the dealer using regular oil @ 10k intervals under the free maintenance during warranty program.

As I said above .. this is a common problem with Nissan V6's -- but, its the rear main seal. Obviously cheaper to leave the seal alone and use conventional oils. With an oil pan -- the cost to replace is easy and low .. and with no history of being a problem woudl be a reasonable thing to do.

Highhorse seems to think I may have a poorly stamped (Defective) part? I don’t really understand how the issue could be metal fatigue or warping of the oil pan now after 18 years. If changing the seal does not fix the leak, I will think that I made some error in changing the seal myself.

Yeldogt, My plan is to check the many oil pan bolts for proper torque & if that is not the problem, buy a genuine Jaguar new seal & drop the oil pan & replace it. I do not want to go back to conventional oil. I like synthetic oil, especially the fact I can change oil only 1x/year. I do it in December when it is cool. I would hate to have to also do it in the HOT summer here.

FWIW, I never had any “free” oil changes @ the dealer. They were not offering any free service with purchase of a new Jaguar back in 2000.

I had changed my oil myself or used an Indy shop b4 I bought the Jag. I decided to use the expensive dealer to do it since this was my 1st luxury car. So, 6 months later 12-2000, I paid the high, dealer price. When I checked the oil the next day it was 1 qt. low! Also, there were some oil stains from dirty hands in the cabin I had to clean up.
I drove it back there & had them add 1 qt. I HAD given them the supplemental sheet that came with my manual, saying my late 2000 model takes 1 liter MORE vs. the early 2000 model. I suspect laziness & they didn’t bother to check the oil level after they put in 7 qts instead of 8. I think I gave them 1 more chance 6-2001 b4 I changed to various Indy shops. A couple years later I began DIY & bought jack stands, used oil containers, etc. I have changed the oil pan bolt with washer every time despite it looking undamaged & have always used genuine Jaguar oil filters.

I never said it was defective (not saying it couldn't be either), it was a general statement of what can go wrong with almost any car after 18 yrs no matter how well you take care of them.

Heck, I replaced my oil pan first off 14 yrs ago, because the PO had managed to ding it pretty good. If you want, check here for another pan... Car-Part.com--Used Auto Parts Market

I do not think I have a damaged or defective oil pan. When I remove it to replace gasket, I will certainly look carefully.

I realize, after thinking about it, that I cannot really “Check the torque” on those 18 oil pan bolts, unless I loosen each bolt & then re-tighten with a torque wrench. So, I will cause an oil leak doing this unless I 1st drain all the oil.

I’m new to using torque wrenches. I just bought my 1st one, a ½” click drive to check wheel nut torque. In that case there is no issue loosening each nut & then re-torquing it. Obviously.
So, the oil pan bolts torque spec is 11-13 Nm which coverts to 8.11-9.59 ft.-lbs.
I would set to 9 Ft. Ibs.

W/o draining the oil, if a bolt was torqued to say 5 ft.lbs, I could easily adjust it to the correct 9 & stop the leak.
However, what about all the bolts that are already correctly tightened or perhaps a bit too tight? Setting my (soon to be purchased )¼” click type, torque wrench to 9 ft.-lbs,
I would then start to tighten an already tight bolt. If that bolt was already @ 9, my TR would click & the bolt would not move. If that bolt had been overtightened to say 15 ft.-lbs, I think my TR would click & the bolt would not move. I’m not sure.

See:


Three Proven Methods of Verifying Torque Specifications
https://www.mountztorque.com/learnin...specifications

Checking torque on already tightened bolts

Checking torque on already tightened bolts- Mtbr.com

&

https://blog.maxprocorp.com/checking-your-bolt-torque

More complicated than I had realized.

I do not want to over tighten & maybe strip one of my oil pan bolts.

I think the “best” method is to loosen a bolt & then tighten it with a torque wrench to the proper specs. Which, in this case, will cause oil to leak out.

My reasoning is if it is possible that a slightly loose bolt is causing my small leak, than one by one making each bolt very loose, even for a minute, will cause leaking & a mess…even if I end up with all bolts tightened at the end. So I would create temporary leaks.

An off the topic note, but since you mentioned torquing lug nuts. Be sure to use a deep well socket so it makes contact on the hexagon on the base of the nut. This way you don't apply your torque onto just your chrome cap and deform it and it starts loosening and deforming.


As for your leak, where is it? ...from the front, side rear? Are you positive its the oil pan gasket and not the crank seal? Oil is a fluid and all fluids take the path of least resistance. Does the leak persist after shut down? Thus, if it only leaks when there is oil pressure on the system, I suspect other than the pan.

If its not the crank, perhaps this may be weeping. A member recently had this issue with part #10 in this thread... https://www.jaguarforums.com/forum/x...r-hose-197251/



https://cimg7.ibsrv.net/gimg/www.jag...55686e9c04.jpg

Iconoclast: Stuff happens .... over a period of years. It's not unusual for valve covers to leak as well. Seals stiffen --- metal pats move.

Do a good wipe off and give each bolt a little push test-- you will be able to tell if any had loosened. Check to see if any leaks come back -- if they do give another push in that location . You are not going to damage anything being careful.

I agree on the OE seal if needing replacement.

Can't explain your lack of maintenance ....... My 95VDP did not come with free maintenance. But, Thought my 98VDP did ... know my 02XJR did. Jaguar provided free maintenance/ service ....... they may have even given me my fist set of pads (front). Filters/wiperblades etc..

I agree on the SYN --- I use it mostly because the additive pac is good for two years. My old cars only go 4-5k a year ... so the oil can be in for 2 years. My V6 pathfinder gets the regular because the cost/trouble and other posable problems fixing the rear main seal are not worth it. I use the high mile oil in it as well

I like synthetic because it makes starting in very cold weather (Omaha in the Winter!!) easier and holds up better in very hot weather. Syns also hold up better with frequent starts in local driving (starting enrichment dilutes the oil; less so today, but still). But I change twice a year.

Any wrench and five minutes underneath will tell you whether your pan bolts need tightening. A very strong light will also confirm or deny leaking seals fore and aft.