What Engine Oil to use ?

[Rob739]

It is coming up to oil change time and I am wondering what oil (particularly the grade) to use.

Standard spec. back in '66 was 10W40 Castrol GTX, bust most oil manufacturers and classic car magazines seem to recommend 20W50 for classics nowadays. I am wondering if this is just because it gives a satisfying jump in oil pressure in our older engines, or if there is another reason. My S1 4.2 oil pressure is reasonable at 45psi when hot using 10W40 GTX, but I know that oil pressure is not everything as flow is important too.

Similarly, most pundits seem to suggest that semi-synthetic is a good (but perhaps unnecessary) upgrade over plain mineral oil, but that fully synthetic can cause problems with oil leaks past older technology seals and rings.

Does anyone have any positive or negative recommendations for oil to use ?

Thanks and regards,

Rob

[DaveK]

Rob,

I have always used the Castrol GTX high mileage for no other reason than that seems a good oil to put in, nothing scientific thats it.
As long as you have the correct level and change the oil and filter regularly I really don't think it matters that much as long as you use a good oil in the first place.

Dave

[V12Graham]

Hi Rob

Just to say I agree, oil is very much a personal thing, I remember in my younger days I put Duckhams in everything I ran but I think it was something to do with the novelty of the green colour and the free jugs they often gave away!!
One sugestion is if you're in the habit of putting your Jag away for the winter it's a good idea to change the oil prior to lay up then you've got nice clean oil sitting in the bearings which should help to avoid corrosion which can some times occur in idle engines.

Best wishes
Graham

[MrNpw]

Hi Rob

Having similar thoughts with regards to engine oils at the moment .

Did you come to a conclusion ?


Nick

[piman]

Hello Rob,

"Standard spec. back in '66 was 10W40 Castrol GTX"

My memory of the sixties is that multigrade was always 20W 50?

I too always used Duckhams as it had a very good reputation, but now will use any quality 20W 50.

Alec