Frank, as always, thanks for your informative reply. I did a search on the forum using “oil” or “oil pressure” as keywords and it came back with a ton of threads for previous discussion on this issue. Lower OP at higher temperature seems to be a common problem experienced by many drivers. Or maybe I shouldn’t call it a problem.
Summer temperature at where I live goes to 38~39, but I normally don’t try to avoid hot days to drive. As long as it is not raining, I am happy to take the Jag out for a spin. There are also much less motor bikes on the mountain roads in those hot days.
I experienced the same low OP problem when stopped at lights, after a few hill climbs on ~35 degrees days. I had to push the gear to “N” to increase the rpm to about 900~950 or even open the throttle slightly so the OP wont drop to <10. And on the 80km/h cruising back home, OP was always a tad lower than 40. That is why I feel like trying the Penrite 20W60 out if I still do that much of hill climbs in summer.
Penrite 10W60, 15W60 and 20W60 racing oil are all full synthetic. Working out at least 3X more expensive than the 20W60 mineral oil. I will see if I like the 20W60 mineral oil before I consider those really expensive stuff.
Try the 60 oil by all means. If it’s a really hot day and the oil is very hot the pressure will be very low. I decided not to worry unless the lamp begins to flicker. There’s a reason most cars don’t come with a real oil pressure reading! And most don’t tell the real temperature either. Oil pressure is more about learning how it behaves and noticing if something goes wrong.
If you are really worried about the oil not getting everywhere (which is all it has to achieve, especially on a hot day at idle), make sure it can’t roll away and have a look at the exhaust cam. If it receives oil the rest does, too; the camshafts are the last items to receive oil, which has to be pumped past the rear main bearing first and then up the thin feed tube. As long as they are lubricated, and at idle 10 psi is plenty when the oil is thin, the bottom end has all the oil it needs.
That being said, if it should ever become alarming it is time for new bearing shells. But as long as you meet the 40/3000 in normal driving and the warning light is not on at idle it’s not going to explode.
If anything, as Pekka said, your oil is a little hot! I had a failure once (in the relief valve) and drove 20kms at 80-100 kph with no issues, the oil pressure never higher than 20 and about 0 at idle in gear, around 10 in N. So try the oil, but no immediate need.
Is it the cam where I can see after opening the oil filer cap? I checked it once after the engine cooled off, there was some oil in there. I was not sure if there was too much or too little though.
I will calibrate my IR gun and measure the temperatures again next time.
Yes, if it happily splashes around in there while running in my eyes you should be fine - if it’s dry (besides what pools in the bottom) then you’d have a problem. There’s no too much, and there is always some oil as the drain is higher up. You’ll see when you look inside.
But… really no need to check.
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Which raises the question, Fan Yi - when is oil pressure a problem…
Jaguar put in the low oil pressure warning lamp, which start flickering at around 5 psi - so above that, the pressure in idle is deemed adequate; oil to all relevant points. And if the pressure also meets Jaguar specs, 40 psi at 3000 rpms it is as good as it gets - and there is nothing indicating that 10 psi in idle is inadequate. For that matter; what sort of oil pressure do you actually want…
As David says, no immediate need - your oil pressure is fine. With worn bearings, as shown by lower than spec oil pressures, increasing the viscosity is a fair response - awaiting bearing overhaul. But increasing viscosity just for the sake of it is an endless upwards spiral - and excessive oil pressure is counterproductive.
If you really care; verify gauge reading with an external pressure gauge - that will at least verify that your gauge reading is in fact correct…
Frank
xj6 85 Sov Europe (UK/NZ)
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Thank you gents for all your continuous reply and support! Jag-lovers forum has to be one of the information resources help me to make the decision of taking ownership of a classic jag. The other one should be the living with a classic youtube channel.
I have my 71 xj6 for only about 3~4 months and still getting to know it. The previous owner had it for 13 years, but only drove it for 1400 miles (I thought he said 4000, but after checking the receipts, it is more like 1400). The first time I took it on the motor way for a proper warm up, I really didn’t feel safe. None of the gauges responded normally, most of them were sleepy and the ride felt rather stiff. Not to mention the smell made me feel like sitting on a petrol bomb.
I took it to a local Jag workshop for a general check and service 2 weeks before Christmas, so I still had the gift funds in case I need to pay for a big bill. Surprisingly, nothing major was found. The shop owner told me to just drive it more, then the car would be more alive. I took his advice. After a few more 20km healing trips, and some mild hill climbs in the weekends, the big cat slowly woke up. The gauges and panel lights all work normally and show repeatable responses in the same driving condition. I feel it is a better time to find out how well the car is working and ask for suggestions from you more experienced owners.
I did a simple calibration on my IR gun tonight, pointing it at the black surface of water cattle until the water boiled. It showed 105.3 at the boiling point.
And a new set of temperature in engine bay is obtained after another hill climb, with the engine running:
A: 360~370 degrees
B: 330~340 degrees
C: 105~108 degrees
D: 92~96 degrees
E: 98~102 degrees
F: 80~82 degrees
G: water rail @ 86 degrees
H: Engine block at exhaust side, 102~106 degrees
The front exhaust manifold is still 20~30 degrees hotter than the back one. The cam cover at the exhaust side is about 10~15 degrees hotter than the intake side. Radiator and water rail temperatures are lower than when heat soak happening.
Seems like your IR is reading some 5,3C too high, Fan Yi - though it may just be erratic? But there is still nothing alarming in your readings - though a more systematic check on the coolant temps at various points may reveal something interesting…
Frank
xj6 85 Sov Europe (UK/NZ)
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Fan Yi,
from what you’re telling us the only thing your cat is suffering from is a serious state of LUAIS - lack of use as intended syndrome!
Exercise the engine carefully. Even with a FI engine there may be carbon residues that you don’t want to go off in flakes let alone ignite. One hour drives at increasing loads will do wonders. Maybe add one load of FI cleaner and maybe reduce the oil change interval for the first time. Even 7 quarts of oil come cheap compared to engine damage.
Jaguars also seem to defy the rules of simple electrics. As a matter of fact Jaguar electrons tend to become sleepy. This doesn’t only relate to guages, but also switches and even the windscreen wiper are known to sometimes resume to forgotten operation mode, if used regularly.
Best thing so far: you seem to have found a gem of a Jaguar mechanic! Many of us will have had the picture in their mind of a mechanic recognizing in you the man paying for his kids’ college!
So enjoy the car and - even if it just does as it should - stay with us on the forum, get acquainted with your car, its quirks and the technical issues more or less likely to come up and, most importantly, overcome your instinct to fix all might-be defects. Watch ebay to find parts that look like they could replace worse parts on your car, check out parts suppliers with minor orders to find out about their expertise and reliability and wait peacefully, until the first serious issue will hit you … it will, for sure, but you won’t be alone.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
I look forward to visiting my son and grandson five or six miles from you when covid is under control. I’ll bring a heavy lead boot for your right foot to help you enjoy the XJ more
Plz PM me when you come over. I have a few Asahi in the fridge to trade for your lead boot.
Thanks Jochen. I will learn more from you guys and take good care of the JAG.
I got the engine oil and filter changed about 250 miles ago and will change the oil again when it reaches the first 1000 miles with me. The filter is different to the switch on ones for later xj and more difficult to get locally, so I plan to change it every 3000 miles.
I run the car on a road with gradually increasing demand. There is a 10~15 min drive on 60~70 km cruising sections before I get to the hills. So The engine can be thoroughly warmed up before I need to shift sown to 2nd and open throttle.
The new engine oil turns black quite quick after just a few hill runs.
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While there is certainly build-up of carbon etc during long ownership with a dawdling driver, Fan Yi - and when released must go somewhere; over time the sump collects a lot of stuff. So when new oil is put in; stir-up in the sump will quickly contaminate new oil - irrespective of recent contaminants…
Frank
xj6 85 Sov Europe (UK/NZ)
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My (never new) cars never have clean oil after a change and a few miles, what‘s left in the engine is always enough to darken the new oil.
I was seeing clean oil after running for the first time when I rebuilt and completed cleaned my new engine. At least a quart of old oil will always remain.
Since it did not blow up on the first hill climb, I declare it safe to drive and also safe to thrash as much as you like.
It’s long been my impression that engines are very tolerant of “dark” or dirty oil. Transmissions, not so much. It’s even been suggested that engines typically have chains driving the cams rather than gear trains not just due to costs but primarily because gear trains require scrupulously clean oil.
More likely the fact that gear trains require a heck of a lot more precision to set up and run quietly than chains, so more cost effective.
Chains are dirt cheap, light, relatively silent and efficient. They can be tensioned to take up slack. If they wear, they can be changed easily, and wear can be compensated. So when they wear, and they do that, it’s a few dollars for parts.
Gears have more thrust surfaces and engines mostly glide on a cushion, so I can imagine they tolerate more abrasives in general. And the black is mostly soot so not that bad I’d think.
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Indeed, the oil doesn’t lose its lubrication qualities being dirty, Kirbert - the reason for changing the oil regularly is more related to the build-up of corrosive elements over time…
Incidentally, long time ago, I holed the sump against a curb (careless!), had it repaired and cleaned of (lot of) accumulated gunk. After that, as opposed to earlier changes; the oil actually stayed clean between every oil change for some years - gradually getting more dirty. Hence my comments - though of course piston blowby through wear will invariably dirty the oil…
Frank
xj6 85 Sov Europe (UK/NZ)
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I see the point there but this seems not to be the case in motorcycles.
One might argue that a motorcycle will never see the mileage a car or a truck will, but almost all them share the same oil with the engine, wet clutch included.
When I rebuilt my Yamaha the gearbox had no signs of wear what so ever, even after 200.000 Km.
And then it’s the legendary Ducati Desmo, that used gears to drive the valve train.
Oh me. bad memories of the gear driven cam shafts. fiber gear for silence. Yup, very quiet when shucked f teeth. A few in my past…
Wnm in to such an engine, I sought an alloy replacement wherever possible…
There are chains and there are chains. Cheap single row. doomed to early failure. double row, better.