1990 Jaguar XJS V12

Boss302fan · Oct 3, 2013

I recently purchased a one owner 1990 Jaguar XJS V12 (30K miles)and it has used a steady diet of 20W50 oil all its life. No current oil leaks.

I live in Wisconsin and am considering using Mobil 1 High Mileage 10w40 because I want a little lighter oil then 50 weight and want to avoid any potential oil leaks. What do you guys think about this weight? I know some people use 10W30 but I am worried about going that light with this engine... Thanks.

GatorJoe · Oct 3, 2013

That's the oil I use and it seems perfect. I talk to a lot of Jag owners and many are moving away from the 20W50 to 10W40.

TechnoLoGs · Oct 3, 2013

Originally Posted By: GatorJoe
That's the oil I use and it seems perfect. I talk to a lot of Jag owners and many are moving away from the 20W50 to 10W40.

had an XJ6 once (1985) and the old-school Jaggers will beat up upside the head with 20W-50, 20W-50, 20W-50, and 20W-50 some more.. as it indeed appears ot be what Jag spec'd for the car.

And yes, most use 10W-40 or 0w30 GC. With no issues and better performance. Though maybe a romance is to 20W-50?

TechnoLoGs · Oct 3, 2013

You will probably notice the gauge sit in the middle (40Psi) with a 10W-40 (or xW-40......) vs somewhere in the higher 3/4 with 20W-50 like mine did at cruising speed. Then again, I had the 4.2.

GSCJR · Oct 3, 2013

10w-30 should be fine.

nitehawk55 · Oct 3, 2013

Rotella T6 in 5W40 might be a good choice too .

901Memphis · Oct 3, 2013

Mobil 1 High Mileage 5w30 is on the upper end of the viscosity range too.

zeuloa · Oct 3, 2013

How about Mobil 1 15w50 or 0w40?

TechnoLoGs · Oct 3, 2013

I used Supertech 10W-40 in mine and it seemed about perfect with oil pressure.

4.2L I6

CATERHAM · Oct 3, 2013

I believe Jaguar started specifying the 5w30 grade in the last years of production of the V12 and that's the grade I'd recommend.
You've got an OP gauge so there should be no problem making sure you're maintaining adequate oil pressure.

IIRC in another thread a couple of years ago a member ran Mobil 1 5w30 without issue in his V12 Jag.

Boss302fan · Oct 4, 2013

Thanks guys...

This car has always had 20W50 and most people I know, have used that weight. Some are now going to a 40 weight oil.. I think I will try Mobil 1 High Mileage 10w40 for an OCI and see how it goes. No leaks or seaping and I want to keep it that way. LOL. Was also thinking about trying Mobil 1 Turbo Diesel Truck 5W40. I want to make sure I do not go too thin and then my oil pressure will be to low. Thanks again...

aquariuscsm · Oct 4, 2013

If all is well currently,stick to the usual 20W50.

Boss302fan · Oct 4, 2013

Originally Posted By: aquariuscsm
If all is well currently,stick to the usual 20W50.

I live in WI and the temps are much lower here then when the car was in NC. I just think a 40 weight will be better for this climate.

CATERHAM · Oct 4, 2013

In a 40wt oil the ideal choice would be Mobil 1 0W-40.

davebarnum · Oct 4, 2013

So this is not intended to stir stuff up, but honestly, what would happen if you ran, say, a 0w20 synthetic in this. Aside from improved fuel economy, that is.

Just curious actually.

CATERHAM · Oct 4, 2013

Originally Posted By: davebarnum
So this is not intended to stir stuff up, but honestly, what would happen if you ran, say, a 0w20 synthetic in this. Aside from improved fuel economy, that is.
Just curious actually.

You couldn't ask for better lubrication on start-up particularly in the winter. The limiting factor would be maintaining adequate oil pressure once up to normal operating temp's.
If the engine is in good shape you likely can particularly in the winter months. In a vehicle with an OP gauge there is no risk in trying especially if you already know how much excess OP you have running a grade or so heavier.

I've run a 0W-20 in my Bimmer during the winter months in the past. A 5W-20 was spec'd as an option for my '86 Porsche back in the day for ambient temp's below freezing and of course no high speed driving.

aquariuscsm · Oct 4, 2013

Originally Posted By: CATERHAM
A 5W-20 was spec'd as an option for my '86 Porsche back in the day for ambient temp's below freezing and of course no high speed driving.

I've always wondered about that type of spec. My car's the same way,FSM specs 5W30 for temps below freezing only,and no extended high speeds. My work commute is now 44 miles interstate 6 days a week. At 70mph engine is spinning just above 3k rpm. I'm guessing that's "extended high speeds". Thicker oils are what is best for my driving regiment I figure. I hardly ever do any in-city stop and go driving.

CATERHAM · Oct 4, 2013

Originally Posted By: aquariuscsm
Originally Posted By: CATERHAM
A 5W-20 was spec'd as an option for my '86 Porsche back in the day for ambient temp's below freezing and of course no high speed driving.

I've always wondered about that type of spec. My car's the same way,FSM specs 5W30 for temps below freezing only,and no extended high speeds. My work commute is now 44 miles interstate 6 days a week. At 70mph engine is spinning just above 3k rpm. I'm guessing that's "extended high speeds". Thicker oils are what is best for my driving regiment I figure. I hardly ever do any in-city stop and go driving.

Using ambient temp's and restricting high load use (high speeds) is all about predicting operational viscosity.
But if you have an oil pressure gauge and know how to properly use it then there is no guessing involved. Once you know the minimum OP level that represents a safe minimum operational viscosity then it's very easy to determine how light an oil you can run and under what conditions.

andyd · Oct 4, 2013

Does the engine use oil between changes? Does it leak? How much? Light oil will lower oil pressure, but clean out sludge and un-stick the oil control rings. I hope your pockets are deep and you are knowledgeable about the car.

I want a stock series 3, XJ6 again. It is Marina's favorite car. Her kitty, she called the first one. The body lines are so smooth and classically done, and a 4 something liter I-6 with DOHC that is as nice looking as the car. Even if it doesn't run. It was a 25th anniversary present. It was my first fuel injected car. Had I known then what I know now about Bosch fuel injection,I would have had a better ownership experience.

Boss302fan · Oct 7, 2013

Originally Posted By: andyd
Does the engine use oil between changes? Does it leak? How much? Light oil will lower oil pressure, but clean out sludge and un-stick the oil control rings. I hope your pockets are deep and you are knowledgeable about the car.

I want a stock series 3, XJ6 again. It is Marina's favorite car. Her kitty, she called the first one. The body lines are so smooth and classically done, and a 4 something liter I-6 with DOHC that is as nice looking as the car. Even if it doesn't run. It was a 25th anniversary present. It was my first fuel injected car. Had I known then what I know now about Bosch fuel injection,I would have had a better ownership experience.

No leaks and everything has been maintained and well taken care of. The original onwer really took care of this XJS and hopefully it keeps running like it should.

I did the OCI with Mobil 1 High Mileage 10w40 and it runs very smooth and quiet. Looking in with the oil cap removed, shows like it is polished and brand new... It was always serviced by the Jag dealer... Hopefully I got a good one. LOL. The body looks like a one year old car with zero rust. I'm going to keep my fingers crossed everytime I drive it. LOL...

1990 Jaguar XJS V12

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