interestingly the derivative of this engine that was used in Ford's T bird and other models uses 5w-20. curious if there was an change in clearances or pump capacity. did the later Jaguar uses for the engine such as the XK ever use the 5w-20.

one thing worth noting is that regardless of which synthetic liquid miracle used, the narrower the viscosity range, the better. a single viscosity oil will have virtually no shear issues over time. there is no need for viscosity modifying molecules that break down with use. consequently, if your ambient temperatures do not require a 0w or 5w using a 10w-30 means the oil is less prone to shear. some of the synthetic manufactures have trimmed their product lines to only have the 0w-whatever. they claim that if you need 15w-40, their 0w-40 covers it. yes, it does until the shear occurs and this is not apparent in most oil analyses. it can be seen by watching the pressure gauge if it works.

 

just to add, it is not possible to make the new 20 multi weight oils without using synthetic blends at minimum. if you have an engine that specifies these types, do not go cheap on the oil. as for the 5w-30, regular Castrol is one of the best. most people simply do not realize what severe service is and do not change the oil soon enough. my manuals both make the distinction between the regular and severe service usage. this is where yearly service gets bad for any vehicle as it is going too long without a change.

 

 

If I recall correctly the owner’s manual has a chart listing the viscosity levels for a given temperature range use that chart to select the correct viscosity for the temperature range you are in. I attached a link to assist you in better understanding engine oils/lubricants and viscosity levels. In no way am I suggesting what oil to purchase but I use Mobile 1 Syn 10w-30 and I have a little over 154,000mi on both of my Jags.

Link https://www.bobistheoilguy.com/

 

^^^^^ one thing I might add, is if a person is in the habit of changing the oil at least once a year on seldomly driven cars, then change it BEFORE the car is being mothballed for the winter. Even with minor or minimal blow-by, oil gets contaminated with acidic residue from the combustion process. Letting your engine sit in this acid bath for 2-4 months is not advisable.

If your driving is mainly seasonal, change the oil at the end of your driving season. Your bearings will thank you.

Z

 

ditto, this is the reason that we do the same with boat engines. of course there are those of us who drive in the cold weather as long as the criteria is met of no salts on the roads nor snow. in this situation it is still advisable to change the oil prior to the cold season as there will be much more condensation and less vaporization of water and volatile pollutants.