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The owners manual shows a sliding scale of possible oil viscosities depending on what is the typical climate.
For my range of temperatures, I use Mobil 1 0w-40, or if the oil change is happening at the beginning of summer, I use Mobil 1 5w-40.
The car is a daily driver so my mileage piles up rapidly. The best oil I’ve found for a wide range of temperatures is the 0w-40.
The benefits of a quality synthetic vs conventional oil have been debated ad nauseam, so I won’t address those except to say that synthetic oils perform very well at high temperatures. Conventional oils don’t.
Of course all the above is for a new engine ...mine has 112k and a little piston slap which disappears in winter when the average temp is about 5 degC and the oil thicker on start up. . So I am changing the oil from 5w30 to 10w40 which I hope will loose the slap.
Of course all the above is for a new engine ...mine has 112k and a little piston slap which disappears in winter when the average temp is about 5 degC and the oil thicker on start up. . So I am changing the oil from 5w30 to 10w40 which I hope will loose the slap.
I’ll see your 112k and raise you another 70,000 miles.
My 2002 XKR has 181,384 miles on it as of today. And yes, of course there is a good bit of piston slap when the engine is cold.
with both the Mobil 1 0w-40 and the Mobil 1 5w-40 the piston slap goes completely away when the oil temp reaches about 150 F and the coolant is 130 F or more. Normal operating temp for the oil is 210 F + / coolant at 185 F +. And by that time the piston slap is completely unnoticeable.
Your engine, your call, of course. But I’d be cautious about using any 10w-40 oil in these engines. Too thick, especially at startup. And for numerous reasons, not recommended by the engineers who designed the engines.
The piston slap when the engine is cold
may certainly be annoying, but it has no performance or longevity connections.
In any case, a good practice with any engine is to refrain from spirited driving until the engine is fully warmed up.
As long as these cars are driven frequently, one can hardly go wrong with them. It’s the cars that sit for weeks or months that seem to have the most issues.
Its not so long ago that we were all throwing 20w50 into engines so I dont see a change to 10w40 being a big deal, The makers only went away from 20w50 to make small improvements to MPG.
Any way I bought the oil so I am going to try it ..just waiting for weather to improve.
Of course all the above is for a new engine ...mine has 112k and a little piston slap which disappears in winter when the average temp is about 5 degC and the oil thicker on start up. . So I am changing the oil from 5w30 to 10w40 which I hope will loose the slap.
10-40 for an older car with 100K miles+.
Because the recommended is thinner, but recommended on a new engine with new clearances, our engines are now worn with larger clearances so slightly thicker oil is always better, along with regular oil & filter changes 👍🇬🇧
I'm not surprised there is much debate/confusion over 'what oil should I use'. I've pulled this from the '98 Vehicle Care (ROW):
For our 'temperate' climate, it appears that any of xxW-40 viscosities is just fine, and the note re synthetics at higher temps is in accord with zray's comments above.
For a couple of years after I started to do my own servicing, I was using 15W-40, then went to 10W-40 (both semi-synthetic) as that was what the local motor factor's book recommended. I recently found a couple of invoices from the early days of dealership care (~2005) , and they used Mobil S 5W-40 fully synth, so it looks like I've been going backwards...
I do think the trend to thinner and thinner is driven more by fuel economy figures than what's best longer term for the motor, though.
Oil filter? I also use Jaguar's EAZ1354, but whatever you choose, make sure it has the non-return valve.
Last edited by michaelh; Mar 26, 2023 at 12:11 PM.
Zray.....you wont get any more pressure 75 psi is the opening pressure of your oil pressure relief valve. ( spring and ball).
BUT the thickness of the oil being sprayed onto the cylinder walls with be thicker which will I hope help with the piston slap.
just found Castrol Edge SUPERCAR OIL 10W -60 go figure.....
Last edited by Pistnbroke; Mar 27, 2023 at 03:39 AM.
It won't hold that pressure when the engine gets really hot.......
What do you call “really hot” ? 215 F is about as hot as my coolant has registered in the hottest days of 115 F ambient air temp.
But you’re right . It goes down to 70 psi when the coolant get to about 210 F / 99 C I’ve used a couple of different pressure gauges and sending units without any difference in psi displayed, so it looks to me like the reading is accurate.
Of course, I’m using a synthetic oil which is a better performer at high temperatures than conventional oils. BTW, my oil temp is generally 16-22 degrees F higher than my coolant temperature. No idea if that’s normal.
The reason that there is mechanical noise in a cold engine is that thermal expansion has not taken place yet which closes the clearance gaps. Oil is thicker when it is cold to compensate for this. You want the oil to get thinner as it warms to move through the tight clearances easily and quickly. The first number is merely a "test" result, not a statement of any "initial Cold" viscosity. Many great oils labeled as 10W or 15W also pass the test to be called a 5W or even a 0W. They are marketed a certain way in most cases and in others and sometimes in conjunction with specific additives to conform to the rules to be called a 5W or 0W legitimately.
If the engine gets quiet after reaching operating temp which is not often full oil temp BTW, then there is no reason to go to a thicker oil. Efficient engines are tight engines. The Aston version of this engine is built much looser and requires thicker oil at full temp.
Related: Wrote a while back here that engine rings are cheap and easy along with a head refresh. Bearings, rods and cranks are not. Heavy oil for the wrong reasons makes a simple ring job into a rebuild or replace. Thick oil can cause damage to bearings and journals.
