Following a long & fast (400 mile) run in our 3.4 Mk 2 whose oil I
had just renewed with a GM semi synthetic, I was rather horrified
at the oil consumption, which went from a reasonable 300 miles or
so per pint to about 100 !
Topped up with about half a gallon of 20/50 as I had no alternative
(the gauge needle was dipping alarmingly on sharp bends !), since
when the consumption has reverted to more or less normal.
Anyone else found this with synthetics ?
Regards to all,–
Anthony Richards
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
Anthony, you write
“… Following a long & fast (400 mile) run in our 3.4 Mk 2 whose oil I
had just renewed with a GM semi synthetic, I was rather horrified
at the oil consumption, which went from a reasonable 300 miles or
so per pint to about 100 !”
What grade was the GM oil? What has the engine been running on since its
last rebuild? What filter & oil change frequency?
Yes, most synthetics find any leaks anywhere! Why bother with them in well
worn engines like these?–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.
Anthony Richards wrote:
Hi Guys,
Following a long & fast (400 mile) run in our 3.4 Mk 2 whose oil I
had just renewed with a GM semi synthetic, I was rather horrified
at the oil consumption, which went from a reasonable 300 miles or
so per pint to about 100 !
Topped up with about half a gallon of 20/50 as I had no alternative
(the gauge needle was dipping alarmingly on sharp bends !), since
when the consumption has reverted to more or less normal.
In reply to a message from Anthony Richards sent Thu 23 Sep 2004:
Anthony,
I agree with Alex; why bother? I may be totally wrong about this,
but I think the major selling point of synthetics is their
purported longevity: they last twice as long (and cost twice as
much as mineral oils), so you don’t have to change the oil as often.
At equal viscosity ratings (say 20/50), a synthetic oil looks like
water compared to a mineral one, so it stands to reason that it
will leak or blow by more easily. As for the claim that
this ‘‘lightness’’ increases engine performance by diminishing
resistance, I think it’s hogwash.
Aside from leakage, the only nightmare stories I’ve heard
concerning synthetic oils had to do with its tendency to seep into
(and destroy) the clutch plates on motorcycles equipped with an
internal hydraulic clutch.–
The original message included these comments:
Following a long & fast (400 mile) run in our 3.4 Mk 2 whose oil I
had just renewed with a GM semi synthetic, I was rather horrified
at the oil consumption, which went from a reasonable 300 miles or
so per pint to about 100 !
Anyone else found this with synthetics ?
–
Jacques B / 62 MK II 3.8 Auto
Saint Augustine, Florida, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Jacques B. sent Thu 23 Sep 2004:
If the viscosity ratings are the same, then the synthetic oil will
not leak or blow by more easily simply due to being thinner -
because it isn’t thinner.
If synthetics really do leak more than an exact equivalent grade
mineral oil then there is some other mechanism involved here.
In modern, high revving, engines with closer machined tolerances
and smaller clearances then thinner oils are the way to go and do
reduce resistance. However this is no benefit to an XK, which needs
a heavier oil, be it synthetic or mineral.
The original poster did not state what grade of synthetic he was
using, it would help to know.
I’ve run my car for a while now on a 10W/60 synthetic (after buying
50 litres) without any problems. Currently she’s off road, but has
a lower cost 20W/50 mineral oil in the sump and (no suprise) runs
equally well on that.
I suspect that she burns a little more of the mineral oil, about a
litre every 1000 miles, but I wont know until I get her back into
regular use. In theory, a 10w/60 has a different viscosity at a
given temperature to a 20w/50, so I would have to be careful about
drawing direct comparisons.
Regards,
Andy–
The original message included these comments:
At equal viscosity ratings (say 20/50), a synthetic oil looks like
water compared to a mineral one, so it stands to reason that it
will leak or blow by more easily. As for the claim that
this ‘‘lightness’’ increases engine performance by diminishing
resistance, I think it’s hogwash.
–
Andy Blakey 1983 XJ6 III 4.2 Auto (UK) '‘Jane Seymour’
London, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from AndyBlakey sent Thu 23 Sep 2004:
My vote is with Andy totally as regards viscosity equivalence
issues and utitlity in XK engines. AJ16 engines, being more modern,
can benefit from thin and stable synthetics but in the XK the low
visocsity synthetic (which I’m assuming was used) is
counterproductive for the most part.
As for motorcycles - the vast majority have ‘wet’ multiplate
clutches and for modern stuff synthetic is mandatory (almost) and
certainly not a clutch issue. What WAS a clutch issue was some of
the aftermarket additives such as colloidal graphite and some types
of slicone stuff on wet clutch plates–
Peter Crespin 94 X300 Daimler / 66 2+2 ‘E’
Buxton, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
In reply to a message from Anthony Richards sent Thu 23 Sep 2004:
Hi Everyone,
Thanks for the responses, most of which agree with my thinking !
To answer the questions, the semi synth oil was a 10-40, which had
only just gone into the engine, along with a new filter. I’ve not
had the car long so don’t know what was in it before, but assumed a
20/50 ordinary oil.
The engine has only done around 12K since being rebuilt and runs
very nicely.
Regards to all–
The original message included these comments:
Following a long & fast (400 mile) run in our 3.4 Mk 2 whose oil I
had just renewed with a GM semi synthetic, I was rather horrified
at the oil consumption, which went from a reasonable 300 miles or
so per pint to about 100 !
Anthony, you haven’t been comparing apples with apples. The grade can make
a huge difference.
Our XJ12 and 4.2 are now both running Mobil 1 V twin (20/50) with very good
consumption. I’ve switched to it because it’s claimed to be free of VI
improvers, has a spec that is better suited to old XKs, and in this country
it’s actually cheapest synthetic of all.
I don’t know of anyone else on the list using it.
Here’s something I found the other day -not directly in point but still of
interest:
Anthony’s message includes
"…To answer the questions, the semi synth oil was a 10-40, which had
only just gone into the engine, along with a new filter. I’ve not
had the car long so don’t know what was in it before, but assumed a
20/50 ordinary oil.
The engine has only done around 12K since being rebuilt and runs
very nicely…"
I’ve just read your posts regarding Mobil 15/40 Motorsport. Can you refer
us to any website information on it?
You seem to have chosen it for the same reasons I decided to try the V Twin,
which on the numbers (20/50) should do an even better job as long as we
don’t have to worry about catalytic converters…
What are their relative prices in UK? Motorcycle oils seem to be more
expensive in most parts of the world.
cheers
George
Craig wrote
“…It looks as if we have become multi-forum on this one - there is
more info on this thread on the Saloons forum too…”
In reply to a message from George Morrell sent Thu 23 Sep 2004:
Hi George,
Yes, I’m sure you’re right about the different viscosities.
However, I think in future I’ll just stick to a conventional 20/50;
with the mileage our cars mostly do, the oil changes occur on a
time rather than mileage basis anyway.
Thanks for the help,
Regards,–
The original message included these comments:
Anthony, you haven’t been comparing apples with apples. The grade can make
a huge difference.
In reply to a message from George Morrell sent Thu 23 Sep 2004:
Hi George,
Yes, I’m sure you’re right about the different viscosities.
However, I think in future I’ll just stick to a conventional 20/50;
with the mileage our cars mostly do, the oil changes occur on a
time rather than mileage basis anyway.
Thanks for the help,
Regards,–
The original message included these comments:
Anthony, you haven’t been comparing apples with apples. The grade can make
a huge difference.
I’ll 2nd that notion!–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.
Anthony Richards wrote:
In reply to a message from George Morrell sent Thu 23 Sep 2004:
Hi George,
Yes, I’m sure you’re right about the different viscosities.
However, I think in future I’ll just stick to a conventional 20/50;
with the mileage our cars mostly do, the oil changes occur on a
time rather than mileage basis anyway.
One more .02 worth on the well addressed matter of XK oil consumption. I
just completed a 1200 mile trip in my XK140DHC. Oil consumption was 1 pt.,
fuel mileage 17, average RPM (speedo not working) on highway 2900 to 3200,
altitude 5200 to 7200 feet. Usage includes at day participating in the
JCNA Western States slalom. Engine oil is 20/50 mineral, transmission (Moss
CR overdrive) D4 synthetic ATF, diff had whatever was in it. Car has prox.
20K miles on a rebuild done in '85. I use synthetic sump oil in my high
performance engines, transmissions and diffs. with excellent results but it
does tend to get out of the engines, mostly as mist from the breathers. I
prefer the mineral formulations for street motors as I believe the additive
packages are better for that type of service. No question though, the
engines do show more internal surface soil at 80,000 to 120,000 miles than
engines using synthetics.
Bob Grossman
