Howdy folks, just a quick question to ask if anybody has tried or recommends using synthetic oils. I have a 1973 XJ6 Series 1, and have always been curious as to whether synthetics would be harmful to the engine. Cheers!

Luke

 

I can't think of any case where syn oil was considered "harmful".

Whether or not you'd truly realize any benefit from synthetic motor oil is dependent on a number of factors and has been the subject of many debates.

Some have reported that existing oil leaks seem to drip a bit more with synthetic oil <shrug>

I think its pretty well accepted that synthetic oil flows more easily on a cold start in sub-freezing weather.

I use it, personally, to assuage myguilt over increasingmy change interval from 3000 miles to 6000 miles.

Cheers
DD

 

my opinion is not based on experience because I do not use synthetic oils in my two Jags.

I have been told by experienced Jaguar mechanics to not use them.Synthetics are thinner
and create leaks where none existed.

use 20W50 Castrol in the engine.
use Type FA in the transmission.
use power steering fluid for GM pumps,
use Castrol GT LMA for brake fluid.

ALL mineral oils only.

I use PRESTONE coolant. (do not buy the pre-mixed since you would be paying for water!).

others will have different opinions, that's my story and I'm sticking with it

Jose

 

Yeah that seems to be a common refrain, but fail to see the difference in viscosity between 20W50 Castrol GTX & 20W50 Mobil 1. Would like to hear from experienced 4.2 owners

 

If you repaint the car, would you prefer a 1960s paint formulation?

I use modern synthetics because oil formulations only get better. I use oil from the majors (Castrol, Shell, ... ) because I know they spend a fortune developing and testing their products.

The only time I'd not use a synthetic is for running in (breaking in) a rebuilt engine.

And 20W.. is a bit viscous for our cars unless they are severely worn. I'd go for 10W.., such as a 10W30 or 10W40 Castrol synthetic.

 

I had a Series III XJ6 as a daily driver for many years. Gosh, that was decades ago now !

20/50 is the traditional favorite. I used 20/50 or 10/40.

For the longest time I used GTX. That's what all the other guys used. And, hey, Castrol and Jaguar just sorta go together like a hand in a glove. When GTX become unavailable in my area I moved on to other brands. Shell, Valvoline, whatever. Then I eventually decided to simply buy whatever was on sale that day.

The engine didn't care at all. It ran like a watch and was still running great when I sold the car at 169,000 miles.

Everybody has opinions on oil. Buy whatever makes you happy. You probably have to go out of your way to buy an oil that would actually hurt your engine.

Synthetic? Sure, if you want. The frequency, manner, and distance these cars are typically driven these days makes it unlikely, IMO, that you realize any tangible, meaningful, or measurable difference in your lifetime or the car's lifetime. But, still, if it makes you feel good then I'll be the last one to stop you! Over the decades I've spent a ton of extra money on feel-good things. It is, or can be, part of the hobby. As the years rolled by I decided that saving money also felt good so I've adjusted some of my buying habits ...but that's me

Actually I wouldn't be surprised if the price difference between dino and synthetic isn't as big as it was years ago so, possibly, there's less reason to avoid using it !

Cheers
DD

 

If I'm honest I have to agree, Doug. I have an '04 Suburban with 190,000 miles and runs perfectly fine on factory recommended 5w-30 dino. I have a '04 1-ton diesel pickup and it runs perfectly fine on Amsoil (engine, trans, xfer case, differentials) with 150,000 miles. I am running Amsoil 5w-30 in my Jaguar. But the point where I'm agreeing with Doug is that if you use a name brand oil of appropriate viscosity you shouldn't have any oil related problems. I'm spending more for synthetic for sure, but I'll keep doing it because on paper I believe it's a better oil (in cold weather especially) and it makes me feel good. You used to be able to buy "drain oil" from less than respectable gas stations that was literally the oil from service jobs. They would store it in 50gal barrels for awhile until the big impurities had settled to the bottom and then pump oil from the top. That's one oil I would stay away from.

Dave