Would an XJS using 0/40 Oil or 5/40 Oil use more Oil than an XJS using 10/40 Oil bearing in mind these engines are not Brand New.

Has anyone had to change to a thicker Oil because of this?

 

The 0/40 oil will in most cases thin out quicker over time than the 5/40 oil, and the 5/40 oil will probably be more likely to thin with use than the 10/40 oil, of course this depends on the quality of oil used etc. At the mention of a 0/40 oil thinning, I was wondering if this is what you're experiencing, I have heard from the BITOG forum that Mobil 1 0/40 thins out possibly even to a 0/30 with use. I cannot say I have direct experience of this, just putting it out there, anyone else experienced this maybe?

 

AL,

When that engine was designed, oil specs were BASIC, and the engine was designed around what the market had.

The handbook, yes I know it is out of date today in that area, is still a guide, and based on the ambient temp the car is working in.

So, based on the first scribe line here, 20W50 was the oil of choice in MOST markets back then.

Fast forward 20 years, and ALL SORTS of oil specs are springing up, and that is fine for the engines designed in that era.

Running 15W40, 10W40, in the V12 is just fine, and as you, and most others know, 10W40 is what mine ran.

As engines wear, the move to a "thicker spec" oil is normal practice. Some engines respond to that better than others, and I put the V12 in the "others" group.

When you get bored as you age, and strip down a V12 engine, and note the quality and SIZE of the "bottom end" components, you will understand my passion for these engines, and the 10W40 I use in them.

Even Madams PreHE with 550000kms on the clock still runs 15W40 Mineral oil, and is just as happy now as when it was half that age.

These 0W?? are for the new generation VVT engines, primarily, and that is where they belong. My V6's "can" run that spec oil, but I run 5W30 in both and they are happy.

The X308 guys in our group run 0W40, in all of them.

 

OB, I use Millers 10/60 which I have been told some of the racers use and that has boosted the oil pressure.

 

OB, I can see you are not going to give up until we have the "full-on no holds barred oil thread going over 13 pages thread". I have been trying to resist but I cannot...


If I understand oil weight designations properly, which I may well not, the first number relates to the oil's cold viscosity, the second to its viscosity when warm. Therefore, in very cold winter climates, eg the US northern Midwest, 0w something seems a great idea to me, as it means the oil will flow through the bearings much better when stone cold. Certainly, 5w something would be (I believe) a better very cold start bet than 15w something. The only difference between a cold engine and a hot one as far as wear is concerned, is how well the oil gets round and how well the remaining film sticks to the bearings after the engine is switched off; thus providing a film of oil to protect the cold engine on starting until the oil pressure builds.


My engine has done about 120,000 miles, all but the first 30,000 as my car. When I bought it the car was 13 years old and had done only a few miles a year, mainly about 5 miles each way to the golf club in Scotland near where its first owner lived. So it was in a fairly cold by UK standards area, doing mainly short journeys, and being main dealer serviced, so I am sure it had, at best, a decent make of mineral oil.
Since I bought it, its diet of oil has been 100% synthetic, changed every year, using whatever 100% synthetic made by a major oil company is cheapest, either 0w, 5w, 10w, or 15w -something.


When I redid the cam cover gaskets, there was no discernible wear at all on the cam lobes. The engine uses or burns just about no oil that I can detect, shows no undue crankcase pressure. Plugs show no sign no oil burn. So my conclusion is that as long as the engine has decent oil made by a decent oil major, the oil you use as long as the W-number is not greater than 15, and preferably 10 or lower, it makes naff-all difference !
Greg

 

WELL SAID.

The first number is at 40c, oil temp, and teh secind is at 100s oil temp, which is the "operating temp" of oil in an internal combustion engine/

Any oil manufacturer will have these specs in their websites, and sometimes it takes some digging to actually find them, sometimes not.

I use our Penrite site for what I need.

Time for DRINKS gentlemen.

As for the original ASK from AL, "would it use more oil............"

DUNNO.

Too many factors to even STAB seriously at that one.

Your right foot dictates a lot, and Al's is HEAVY.
Engine condition, valve stem seals, blah blah blah, are just a few as I pour a LARGE one in Al's name.

Main issues with oil pressure in a V12 are the o/rings on the oil pipes inside the sump, on the suction and pressure side of the pump. Simply removing the engine, renewing those o/rings, and reinstalling the engine, will increase oil pressure response time. That pump is MASSIVE, and moves a s*&t loads of oil at very high pressure, so it can compensate for slack o/rings eventuually, and truly, we must remember the age of these items, and the lousy looking after they all had prior to our ownership.

As I said, when you strip one of your engines, it will all be sooooooo clear.

Maybe I need another V12????????, damn.

 

Over the years ...and various cars...I've found that thicker oil can indeed reduce oil consumption, sometimes significantly. I'm talking about going from (let's say) 5/30 to 10/40 or 10/40 to 20/50.

However, I wouldn't expect much, if any, difference in using 10/40 versus 0/40 or 5/40.

Cheers
DD

 

Correct. Our club had a presentation on oil from one of the oil engineers from Esso's research center and his advice was to use the lowest first number you can buy (eg 0W) and the second number as whatever the handbook recommends.

The reason is the low viscosity when cold will be more pumpible and will get oil into the engine as fast as possible on startup, which is where 90% of the wear occurs. Then as the oil heats it is in spec for what the engine was designed for.

I've had a mechanical oil pressure gauge on some cars in the past, and the oil pressure will build noticeably quicker with a 0W oil than a 15W oil.

Climate plays a role too, you would never want to use a 20W oil if you are starting in freezing conditions.

 

Hi Grant

10/40 it is then, if its good enough for 'The Wizard' then its good enough for me and as a bit of a bonus, I can get a 20L Can of 10/40 Castrol Semi Synthetic, so I can do the Merc as well and I already have a Jaguar OEM Filter.

 

Hi Steve

Yeah! I'd love some of that stuff and you do only get what you pay for but when considering the price as well as my low mileage of around 5,000 miles per year.

I'm probably better staying with Magnatec Semi Synthetic 10/40 at half that price.

 

Hi Greg

That is great advice, as I want that happy medium, of being thin enough to get round the Oilways but at the same time thick enough to cling to the bearings, when the engine is not running.

Since you and Grant both seem to agree on 10/40, them I am going to stick with that, so thanks to you both for your help.

 

Hi Grant

Cheers but I don't think that will happen, as I just don't have the Skills required to strip a V12 Engine, not to mention the time, as I have way too many plates to spin at the moment.

And in any event She's running well at the moment, with the first drive of the Year, next week if the Weather permits.

 

Hi Doug

Cheers and I'm going to keep a record of the Oil Consumption if any, although last year She hardly used a drop of 10/40 Semi Magnatec.

 

Pressure is not necessarily a good thing. Think about your garden hose if you kink it, lots of pressure but no flow. If you use oil that is too heavy trying to push it through the bearing clearances is like trying to suck a really thick milkshake through a straw: lots of pressure and low flow.

The oil is pumped into the bearings and the pressure is enough to float the crank or rod journal away form the bearing surface, so there is no metal to metal contact. This is called hydrodynamic lubrication. However, since everything is moving, there is shear in the oil film, and then creates friction. This friction creates heat, so we don't want too much friction. It's wasted energy, and if we generate enough heat it can melt the soft bearing metals.

The ideal state is the oil is thick enough to balance needing enough viscosity to stay in the bearing and lift the metal parts away from each other, and balance off the leak rate out of the bearing.

Too thin, and the oil will leak off too fast and not support the moving parts, too thick and the oil won't flow through the bearing, creating heat and again not being able to keep the metal parts away from each other.

The viscosity needed is a function of bearing clearance and loads imposed on the bearing. The engine manufacturer has calculated this, so that's why I'm always reluctant to use heavier oil than called for unless there is a good reason to do so. Racing is a good reason, where the heat load on the oil is much higher than for a normal road car. I don't often drive my car at full throttle for extended periods

 

I'm sticking with 0w40 in my AJ16 engine. Looking at the recommended oil charts, the 40 weight looks to be the the right option for DC weather and I have yet to have someone explain to me why I wouldn't want the lowest number possible for the cold start number in front of the "w".

I've read the posts here and elsewhere and I have yet to find some response that made any sense to move up to a thicker cold start number.

 

I have 5 autos including the 1990 XJS, a John Deer zero turn mower, 3300 psi pressure washer, 6500 watt generator, 80 gallon air compressor and they all use Castrol 100% synthetic 20/50
A valkyrie Interstate trike a Valkyrie Interstate bike- 6 cylinders and they get Mobile 1-20/50--100% synthetic.

 

I use Mobil 1 0W40 in my 90 XJS V12 with 32K miles and it runs smooth as silk. Great oil pressure and I would swear the engine temps dropped a little bit...

 

Highly likely that they did. The better the oil goes through the bearings, the more heat it dissipates. Oil does around 30 to 40% of the cooling on engines, I seem to recall having read somewhere, and all the cooling on the bottom end and cam generated heat.
Greg

 

I want to say what a brilliant explanation of the situation the first para of your post is. I want to add something that obviously you know, but others may be interested in, if they do not already know it.
Oil pressure is another subject full of myths. In a plain bearing (eg a big end or main bearing being fed oil) the ONLY function of oil pressure is to ensure there is an adequate supply of oil to the bearing. Oil goes THROUGH the bearing because of the hydrodynamics of the plain bearing. What happens in a plain bearing is that the rotation of the inner against the outer (eg the crank against the bearing shell in a main bearing) "winds" the oil through and creates a film of oil between the two surfaces. Think getting your sleeve caught in rollers (or for us over-60s your mother winding the washing into a mangle to dry it !).
The oil film in a plain bearing would be, in principle, perfectly adequate if you just had a 1 foot vertical tube filled with oil being gravity fed into the bearing - as long as you kept the tube full and the oil was thin enough, or the tube thick enough, to let it run into the bearing so the bearing system could "wind it through".
So Steve, as someone pointed out, higher oil pressure does not mean better bearing lubrication if, in fact, the thicker oil is too thick to be properly wound through the bearing by the bearing hydrodynamic force. In effect, think of the shirt getting torn by the mangle because you are holding on to it. As we all know, oil pressure can be sky high at startup on a cold day, and we all know that does NOT mean the lubrication is better at that moment! And that is the reason.
Finally, leaving aside the additive package in the oil that protects the engine from all sorts of nasties resulting from combustion, heat, condensates etc etc, the "winding into the bearing" effect does deteriorate as the oil molecules get chopped up by use ("shear" in Jagboi's post quoted above). This 'chopping up' is a bit like feeding a shirt torn into bits through the mangle, it may not be wound through very easily or well, and the mangle may do some turns with no shirt in between the rollers. This is the main reason, apart from additive package deterioration, that it is wise to change a modern oil after say 7,000 miles, but in principle the more it is changed the better.
Greg

 

I used the same grade for years and it worked well. I had an early 95 with a real pressure gauge and the oil pressure came up quite quickly. In really cold weather it's possible to tell when the oil pressure has come up, the engine sounds different.