Hey guys. I run Castrol SYNTEC in all my vehicles because I'm very particular about that kind of basic maintenance.

My '96 xjr has a small oil leak directly under motor. Haven't had it on a lift in awhile to determine where. I've done 3 oil changes since last spring when I picked it up, all 10W40 SYNTEC.

60K miles on car and I know synthetic oil shouldn't really be used on high mileage motors. It's slicker and prone to leak easier correct?

Should I start using the castrol GTX high mileage instead to slow oil leak down? Just hate the idea of using synthetic routinely then just stopping...

 

I've heard that synthetic tends to slither thru seals and gaskets more easily, yes. But...why not figure out what the leak really is? Might be an easy fix.

I'm not aware of any problem switching from synthetic to dino oil.

Cheers
DD

 

I've been told once you go synthetic you should avoid switching back to regular oil. Im sure others will chime in but thats just what the mechanics I know have told me
ALoha

 

Hey XJ,
I have been using Castrol Edge 10W60 since I bought my '93 and I have noticed no leaks so far . It's almost about to hit 100K miles (159.833 km actually lol )
In my '88 ,I was told to use nothing but 20W50 let alone semi synth .So , your leak might be coming from gaskets , seals rather than oil itself .However I agree and it's a very implausible idea that thinner oil may run thru easily than ticker oil

 

I worked at Jiffy Lube for a few years, and I have heard many claims about synthetic oil. I attended a few meetings with Shell where they would help us sell their product (i.e. Pennzoil) and I brought a lot of these questions with me to ask them. They said, and it makes sense, that other than on a rotary engine synthetic oil will not cause any running problems or leaks because the viscosity is the same. Its the viscosity not they type of oil that makes the difference.

It could be time for you to replace a gasket.

 

60 weight oil is quite thick. Thats almost as thick as gear oil hah.

 

Thanks guys, appreciate the input. I'm moving to Phoenix in less than a month now and want to take my R in for a couple checkups before she's shipped with me cross country.

Once she's on the lift hopefully it'll be easier to pin point where the small oil leak is coming from!

Thanks again,

On another note, I just detailed a recent client's Aston Martin DB7.

It was so neglected, not garaged, and owner put about 500 miles on her in 3 years! Either way, that is a rare sight to see rolling around Buffalo, NY!

She has now been returned to her glory days. The funny thing was it felt like being in our Jags, almost the exact same smell and feel or leather, buttons, etc. Except the roar of the engine upon push button ignition and exhaust bark from that V12 assured me it was slightly more refined than my XJR!

Pics are on my site.

 

I've always been a fan of Astons & the DB7 is a choice model. Did you take her for a spin when the owner left? I hope so

 

It makes sense you would be feeling very familiar with Astons in those years . I bet if you detail or drive a Vanquish you will be seeing how familiar it is
No less resemblance than DB 7 for sure

 

I agrre that synthetic does not cause leaks. But I think it will find a spot that is marginal easier than regular oil because it flows so well. It will also clean away any deposits that may be covering an iffy gasket.

 

Nice comments guys, I'm going to have my brother follow my truck in with my Jag sometime next week because my mechanic can work on it while I'm detailing his Hummer H2 out front, cant wait to do that monstrosity...

Hopefully he can pin point the oil leak. Although it would be a very strange world for me to not see at least some fluid leaks under every last 20+ cars I've owned from Jeeps to Jags! Everyone loves used cars.

I did not get to drive that beautiful DB7, I at least go to back it up and get it up to whopping 2nd gear in the owners mile long driveway. lol.

It was begging to be driven...

 

Phoenix is a good place to live in. Welcome to that place.
by the way about the syntec, i don't prefer to use that one. howeverr since you've said that there's a leak, maybe it is not the syntec caused the leak. before deciding, try first to check your leak in that case you'll prove if the syntec done wrong to your car. you can ask help from those Phoenix auto repair shops mechanics. i know they are all nice.