Let’s talk about 10/40 vs. 20/50 oil. I run 10/40 in mine (what the
FSM and owner’s manuals call for. Runs fine, never had a problem.
I’m curious as to why some choose to run 20/50. I ran 20/50 in my
Alfas and my 5.3 V12, but my AJ16 runs just fine on 10/40. Why
should I switch?–
Roger’95
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// please trim quoted text to context only
No reason to switch AFAIC
I’m not aware of many (any?) who run 20/50 in an AJ16. Pretty common with
the older engines, though.
I run 5/30 in my AJ16.
Cheers
Doug Dwyer
Longview Washington USA
1995 XJR
Let’s talk about 10/40 vs. 20/50 oil. I run 10/40 in mine (what the
FSM and owner’s manuals call for. Runs fine, never had a problem.
I’m curious as to why some choose to run 20/50. I ran 20/50 in my
Alfas and my 5.3 V12, but my AJ16 runs just fine on 10/40. Why
should I switch?
// please trim quoted text to context onlyFrom: “Roger’95” rlaferriere53@hotmail.com
In reply to a message from Roger’95 sent Tue 14 Jul 2009:
I run 20W/50 as that is what the manual calls for in my ambient
temperature environment, but mine is a 5.3L V-12 and that thing
gets pretty dang warm in there. :-)–
The original message included these comments:
Let’s talk about 10/40 vs. 20/50 oil. I run 10/40 in mine (what the
I’m curious as to why some choose to run 20/50. I ran 20/50 in my
–
Jerry Peck, 83XJS/past-54XK140,54MKVII,59MK,60MKII,67E,72XJ6
Ormond Beach, FL, United States
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In reply to a message from Roger’95 sent Tue 14 Jul 2009:
I run 10w/40 in the HE, always have, 20W/50 in the Pre HE, and
0W/40 in the German beast.
The HE has 45psi idle/hot (thermo fans ON), as does the Pre HE, no
idea what the BMW has, the light goes out, who cares?.
Grant Francis
Downunder–
The original message included these comments:
I’m curious as to why some choose to run 20/50. I ran 20/50 in my
Alfas and my 5.3 V12, but my AJ16 runs just fine on 10/40. Why
should I switch?
–
85 XJSV12 (Badcat).76XJ12 (her cat) 94 BMW 740iL (Black)
Adelaide South Austarlia, Australia
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Grant Francis wrote:
I run 10w/40 in the HE, always have, 20W/50 in the Pre HE
Just outta curiosity, why different oils in essentially the same
engine?
– Kirbert
// please trim quoted text to context only
In reply to a message from Roger’95 sent Tue 14 Jul 2009:
I run Quaker State 10-40 in both cars, both are AJ16’s, and 0-20
Amsoil in the van. Always ran 20-50 Castrol in previous Jags, for
that matter in all my cars, don’t know why really, both in So. Cal.
and when I got here. Still have 5 or 6 qts down in the garage.
Switched to QS 10-40 in winter late 90’s when really cold AM car
would barely turn over and had to use heat gun, all I had, to warm
oil pan before it would start.
Lee Murray–
The original message included these comments:
Let’s talk about 10/40 vs. 20/50 oil. I run 10/40 in mine (what the
I’m curious as to why some choose to run 20/50. I ran 20/50 in my
Alfas and my 5.3 V12, but my AJ16 runs just fine on 10/40. Why
–
Lee Murray '95 XJS 4.0 Convertible 2+2, and '96 XJ6
Sherburne, NY, United States
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In reply to a message from LeRoy Murray sent Wed 15 Jul 2009:
I run 20-50 because the bearing engineer at Clevite/Mahle
uses (and recommend) that to provide more protection for the
bearings. He builds the bearings, so he knows what protects
them. Some engines can’t have 20-50, but a Jag V-12 can.–
The original message included these comments:
Let’s talk about 10/40 vs. 20/50 oil. I run 10/40 in mine (what the
I’m curious as to why some choose to run 20/50. I ran 20/50 in my
–
John Aller www.audietech.com 85 xj-s
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In reply to a message from Roger’95 sent Tue 14 Jul 2009:
I recall a test in one of the motorcycle magazines (Motorcycle
Consumer News I believe) from several years ago where they tested
10W40 against 20W50. What stuck in my mind was that the 20W50
ended up running hotter and had lower viscosity than did the
10W40. They attributed the temperature difference to the greater
energy requirement to shear the 20W50 molecules between the moving
and static parts. Their test was probably performed on an air
cooled motorcycle engine, which may have had higher overall oil
temperatures than do our liquid cooled Jags.
The recent requirements to improve fuel economy of new cars is
behind the newer recommendations for thinner oils. The improvement
in lubrication technology and metallurgy also makes it possible to
safely use thinner oils.
I use 10W40 in my 5.3 in the upper midwest without any ill effects
thus far. I have not been able to easily find 20W50 in the brand I
use. I do change my oil frequently as other tests from the same
magazine show that viscosity degrades with usage, again due to the
shearing effect. The one oil that showed excellent viscosity
retention was Mobil 1 synthetic (NAYYY). I do not use Mobil 1
because of the cost and my frequent changes.
I would like to see more oil pressure on my gauge to feel better
about it. However, then I remember the racing engine rule of thumb
of 10 PSI oil pressure per 1000 RPM and my engine runs in that
range. Any lower than that is risky to the engine. Any higher
than that just wastes energy driving the oil pump.
As mentioned by others on the list, the Jaguar V12 engines appear
to be quite robust.
Kern–
91 Classic Collection Convt. (NCHNTRS)
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Kern wrote:
I recall a test in one of the motorcycle magazines (Motorcycle
Consumer News I believe) from several years ago where they tested
10W40 against 20W50. What stuck in my mind was that the 20W50 ended
up running hotter and had lower viscosity than did the 10W40. They
attributed the temperature difference to the greater energy
requirement to shear the 20W50 molecules between the moving and static
parts. Their test was probably performed on an air cooled motorcycle
engine, which may have had higher overall oil temperatures than do our
liquid cooled Jags.
There’s also a possibility that the thicker oil maintains a thicker
coating on internal engine surfaces which serves as insulation,
keeping the heat in.
I would like to see more oil pressure on my gauge to feel better about
it.
Then you need to upgrade to the later style Jaguar oil pressure
sender – the one that shows 50 psi no matter what.
– Kirbert
// please trim quoted text to context only
In reply to a message from Roger’95 sent Tue 14 Jul 2009:
Kirbert wrote:
‘‘Then you need to upgrade to the later style Jaguar oil pressure
sender – the one that shows 50 psi no matter what.’’
Kirbert, I do not know if this is you being humorous or sarcastic.
I am aware that the later sender is merely a switch that introduces
a fixed resistance into the circuit. Several of my other late
model cars have this type of oil pressure indicator. That type of
sender would leave me with more questions than the current Jaguar
gauge.
One question that I have yet to answer is the pressure at which the
switch closes and introduces the ‘‘gauge’’ reading. The idiot lights
that were substituted for real gauges had switches that would
typically close in the range of 4 - 8 psi. They had to be that low
so the lights would not illuminate at idle on a hot day.
Obviously, such a low switch point could invite disaster under
certain circumstances. Assume 3000 RPM at road load cruise on a
hot day and, for some reason the oil pressure drops to 10 PSI. The
light will not illuminate, or the Jaguar ‘‘gauge’’ will not show the
low reading and after awhile, significant engine wear or a seizure
may occur.
I like real oil pressure gauges that change their readings with
temperature and engine speed.–
91 Classic Collection Convt. (NCHNTRS)
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I think we all like the real gauges but, when you stop to think about it,
how often do you hear of oiling system failures?
More important is an accurate coolant temp gauge although…heh heh heh…
Jaguar eventually followed the crowd and turned it into an idiot gauge as
well, on later models such as my XJR.
Funny thing is I’ve grown accustomed to it and it doesn’t bother me. If I
still owned a Jag V12, well, that would be a different story 
Cheers
Doug Dwyer
Longview Washington USA
1995 XJR
Kirbert, I do not know if this is you being humorous or sarcastic.
I like real oil pressure gauges that change their readings with
temperature and engine speed.
// please trim quoted text to context onlyFrom: “Kern” kern@satcarracing.com
In reply to a message from Jerry Peck sent Tue 14 Jul 2009:
This is what my factory owner’s handbook calls for regarding engine
oil:
Temperature range / oil type
-10C (15F) and colder / 5w20 - 5w30 - 5w40
-20C to 15C (-5F to 60F) / 10w30 - 10w40
-10C (15F) and warmer to hotter / 10w50 - 15w40 - 15w50 - 20w40 -
20w50
Plus my Jaguar mechanic says in this area (Florida) the V-12 should
run 20w50 and nothing lower because of the heat - but that is his
unscientific experience of 25 years speaking, having trained at
Jaguar on the 1984 XJS and has been working on them ever since.–
The original message included these comments:
I run 20W/50 as that is what the manual calls for in my ambient
temperature environment, but mine is a 5.3L V-12 and that thing
–
Jerry Peck, 83XJS/past-54XK140,54MKVII,59MK,60MKII,67E,72XJ6
Ormond Beach, FL, United States
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Kern wrote:
‘‘Then you need to upgrade to the later style Jaguar oil pressure
sender – the one that shows 50 psi no matter what.’’Kirbert, I do not know if this is you being humorous or sarcastic.
Neither, being serious. If you’re worried about achieving some
particular pressure reading, you – and your car – would be better
off with a guage that always showed 50 psi.
I
am aware that the later sender is merely a switch that introduces a
fixed resistance into the circuit. Several of my other late model
cars have this type of oil pressure indicator. That type of sender
would leave me with more questions than the current Jaguar gauge.
See, the problem is with the fact that you know why the gauge
always reads 50 psi.
One question that I have yet to answer is the pressure at which the
switch closes and introduces the ‘‘gauge’’ reading. The idiot lights
that were substituted for real gauges had switches that would
typically close in the range of 4 - 8 psi. They had to be that low so
the lights would not illuminate at idle on a hot day.
I think it’s the same switches, so presume 4-8 psi.
Obviously, such a low switch point could invite disaster under
certain circumstances. Assume 3000 RPM at road load cruise on a hot
day and, for some reason the oil pressure drops to 10 PSI. The light
will not illuminate, or the Jaguar ‘‘gauge’’ will not show the low
reading and after awhile, significant engine wear or a seizure may
occur.
Any unexplained sudden oil pressure changes are a cause for worry,
including the pressure suddenly going up. But if the oil pressure
normally sits around 10 psi – such as the Jaguar V12 is wont to do
at warm idle – then having a guage that reads 10 psi tends to incite
owners to do something stupid like toss in oil additives or 60W or
some such. That’s why Jaguar had to go to the dummy sender.
I like real oil pressure gauges that change their readings with
temperature and engine speed.
Good for you. Just don’t apply any preconceived notions of what the
oil pressure should be and you’ll be all right.
– Kirbert
// please trim quoted text to context only
Doug Dwyer wrote:
I think we all like the real gauges but, when you stop to think about
it, how often do you hear of oiling system failures?
On the Jaguar V12, not often – but I had one, a rear main bearing
spun on me when I revved it too much when cold. That was probably an
indication the oil was too thick – at least when cold. I later
switched to synthetic – still 20W-50, but it never seemed as thick
when cold.
More important is an accurate coolant temp gauge although…heh heh
heh… Jaguar eventually followed the crowd and turned it into an
idiot gauge as well, on later models such as my XJR.
An on/off coolant temp gauge? I didn’t know they went that way.
Does the guage very suddenly go from cold to warm sometime after
startup?
– Kirbert
// please trim quoted text to context only
I wasn’t very clear, sorry.
The temp gauge isn’t an on-off fixed reading like the oil pressure gauges
but it is heavily dampened. The service manual says “The temperature gauge
is calibrated to give a ‘normal’ reading over a wide range of temperatures.”
It doesn’t mention the exact range but I’m guessing that anything from about
175�F to 230�F results in the needle staying fixed on the “N”.
Mine will move off the peg quickly after a cold start and head towards “N”
in 3-4 movements. Its not a slow rise but more like “steps”. I’ve never seen
it move past the “N” under any conditions, ever. Other X300 owners have
reported the needle moving over to indicate overheating so at some trigger
point, unknown by me, it does respond to high coolant temp.
Since we’re having heat wave up here I’ll bring my scan tool along and see
how hot it really gets.
Cheers
Doug Dwyer
Longview Washington USA
1995 XJR
An on/off coolant temp gauge? I didn’t know they went that way.
Does the guage very suddenly go from cold to warm sometime after
startup?
Doug Dwyer wrote:
More important is an accurate coolant temp gauge although…heh heh
heh… Jaguar eventually followed the crowd and turned it into an
idiot gauge as well, on later models such as my XJR.
// please trim quoted text to context onlyFrom: “Kirbert” palmk@nettally.com
In reply to a message from Doug Dwyer sent Fri 17 Jul 2009:
My temperature gage starts as the bottom and slowly moves up to a
point where the top of the needle is a bit below the N, and that is
where is typically stays around town.
Had in on the road to Jacksonville and back, about 1-1/2 hour trip
each way, and it would work its way up to where the needle was
centered in the N, then up to where the top of the needle was at
the top of the N.
However, when I got off I-95 and into traffic setting at a red
light, the gage went up to where the bottom of the needle was just
barely above the top of the N. After driving in traffic awhile, the
needle came back down to where the top of the needle was just below
the top of the N. After a couple of stops parking in shade, the
needle came back down to the bottom of the N and a little below the
N.
About 6-9 months ago when it overheated and I had to replace both
thermostats the needle went most of the way up.
Mine definitely does not have any steps - varies with temperature
all the way.
My oil pressure gage varies all the way too. As stated in another
post above, warm/hot idle is around 10 psi and goes up from there.–
The original message included these comments:
The temp gauge isn’t an on-off fixed reading like the oil pressure gauges
but it is heavily dampened. The service manual says ‘‘The temperature gauge
is calibrated to give a ‘normal’ reading over a wide range of temperatures.’’
175�F to 230�F results in the needle staying fixed on the ‘‘N’’.
–
Jerry Peck, 83XJS/past-54XK140,54MKVII,59MK,60MKII,67E,72XJ6
Ormond Beach, FL, United States
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Right, your still have “real” temperature and pressure gauges.
Cheers
Doug Dwyer
Longview Washington USA
1995 XJR
My temperature gage starts as the bottom and slowly moves up to a
point where the top of the needle is a bit below the N, and that is
where is typically stays around town.Mine definitely does not have any steps - varies with temperature
all the way.My oil pressure gage varies all the way too. As stated in another
post above, warm/hot idle is around 10 psi and goes up from there.
// please trim quoted text to context onlyFrom: “Jerry Peck” jerrypeck@cfl.rr.com
In reply to a message from Doug Dwyer sent Sat 18 Jul 2009:
For what its worth - When I put a facelift instrument panel in my
wife’s '89 XJS, I ordered an oil pressure sending unit compatible
with the year of the facelift instrument panel to make sure the
sender was compatible with the panel. When I discovered it was
simply a pressure switch with a resistance incorporated to make the
oil pressure read Normal at all times once the switch closed (6-8
psi?), I ditched it. I then used the oil pressure sending unit
(linear with pressure) from the '89 and added a trimmer resistor to
put it in the proper range to work with the facelift panel. Works
great!
P. S. - Most BMW’s (as well as many others) for the last number of
years have neither an oil pressure gauge or an ammeter / voltmeter -
just a light or message that comes on in case of a malfunction of
either.–
lockheed
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Doug Dwyer wrote:
The temp gauge isn’t an on-off fixed reading like the oil pressure
gauges but it is heavily dampened. The service manual says “The
temperature gauge is calibrated to give a ‘normal’ reading over a wide
range of temperatures.”It doesn’t mention the exact range but I’m guessing that anything from
about 175ºF to 230ºF results in the needle staying fixed on the “N”.Mine will move off the peg quickly after a cold start and head towards
“N” in 3-4 movements. Its not a slow rise but more like “steps”
Does anyone have any idea whatsoever why a car company would do this?
– Kirbert
// please trim quoted text to context only
In reply to a message from Kirbert sent Sat 18 Jul 2009:
Kirbert,
I can tell you that auto makers have done this to reduce
complaints from idiots who don’t understand the temp. will be
hotter under certain conditons.
The manufacturer I work for also did a software flash to
eliminate temp readings from the tire pressure monitoring
system. People would complain that after driving the tires
would have different temps on each corner.–
The original message included these comments:
Does anyone have any idea whatsoever why a car company would do this?
–
Greg 1985 XJS HE DANA rear
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