Has anyone had the experience of fluctuating readings on the engine oil dipstick? The car is parked on level ground, no oil leaks as far as I can see, yet sometimes there's no oil on the dipstick, and at other times it reads normal.
This is rather confusing...

 

While checking the engine oil with dipstick, it is always necessary to start the process only after engine cools down. and if possible start the process, after sitting overnight. cuz many times oil gets sucked into the engine components which takes some times to gathered in sump.

 

I was always told on the Cat to check dipstick after car warms up ? anyone know the correct answer ?

 

There are two sides for checking the oil level
Warm and cold readings . It should be spesified at the dipstick . If you can't figure out let me know I can dig up the manual for you and upload an image for correct reading

 

The key is consistency- doing it the same way every time. The owners manual will state Jag's preferred method.

 

On page 168 of the XJ40 Handbook I still have sitting on my bookshelf more than ten years after selling the car!




Detailed procedure for hot and cold engine.

Graham

 

Agree with everyone else here. Consistency.

Best in the morning before starting the car.

Just after a 300 mile run at 100mph is not going to give a good reading.

Then again, if you had a problem, you would likely be aware of it, before pulling the dipstick.

EX Mrs T, used to pour oil in, until it was visible through the oil add orifice.

This has previously caused 6 cars to self destruct.

Not recommended.

 

I'm familiar wih the proceedures in the manual - it's just that I have heard that sometimes all the oil does not return to the crankcase, and a false reading occurs on the dipstick- something about oil remaining in the oil galleries of the engine...anyone ever heard that?

 

I always try to take a reading before starting the car in the morning.

Or if after an oil + filter change after adding the new oil I will run the car and then recheck the following day.

I tend to slightly underfill and then top up, rather than having to drain which is a PITA.

Slightly under is not going to be harmful short term, greatly over, has a tendency to blow crankcase seals etc.

Just my method at home.

 

So that's why the new ones have no dipstick at all

 

LOL, there is always one, generally located behind the steering wheel.

 

My car has the same problem. No leak. It's not burning, but VERY inconsistent dipstick readings. I play it by ear most of the time, my engine is nice and quiet, no unwanted sounds, and the low oil light isn't on. To me that means plenty of oil. Keep on top of the changes and youll be fine

 

My two cents....

Wild oil reading must be a case of a lot of oil still in the engine or the car is not checked in the same spot every time.

They say don't overfill because you will blow seals etc. There are reported cases of this but they seem rather few and some call it myth all together. For me it is hard to believe that much pressure would build up in the crankcase outside of the oil gallerys the oil pump feeds, overfull or not. I can't see it happening often but just because I can see does not mean I am not blind. Unless your are in T's case where there is not an ounce of expansion space left.

The more dangerous problem with over filling is much of the oil just sits at the bottom of the pan waiting for the pump to suck it back up. The crank sits right above this oil pool. If you fill it up to much the crank balance weights and connecting rods start to slap the oil like a kid slaps water with his hand. Think how fast the crankshaft is spinning...thats a lot of hard slaps that inevetably froths up the oil with air.

The oil pump then sucks up this oil froth and tries to pump it. What results is an oil deprived (and soon to be siezed) engine. I have seen air bubbles and froth come out on the oil dipsticks of these jags from overfilling. If it is only a tad overfull or the car has not been running you might see many air bubbles in the oil on your stick. Frothing I have seen was after longer length of exposure. It started to look like whipped creme, a lot like if you get coolant mixed into the oil.

In my experience it seems to take about a quart or so overfull before this condition will start in normal driving conditons on these engines. I have alos found on my cars that an oil reading done on a cold engine will typically be very close to a reading taken 2 mins after shutdown on a hot engine. I don't worry to much about it because I have driven thousands of miles with the oil level at about a 1/4 quart overfull and a 1/4 underfull with no signs of overfill symptoms. YMMV.

Also just a mechanical thought to your problem. There is a bracket that holds the A/t and oil fluid dipsticks to the engine to keep them from moving and banging around. This bracket is missing on the '93 I just picked up. Could a missing bracket and loose nut on the oil pan (does it have a nut?) be causing the stick to move around and cause inconsistent stick coverage as it is pulled up? [Get your mind out of the gutter]

 

I beg to differ - Jaguar say in the Owners' Manual that there are two engine oil checks - the forecourt check and the overnight check, and I have found, as Jag say in the manual, that these two readings vary vastly as indeed they do in most engines. Trying to substitute checks especially with irregular forecourt readings can be dangerous - I have also encountered these funny and irregular readings frequently.

 

Right. I think the jist of it is consistency as others have said. For me if I am checking my oil to ensure proper level it is on a cold engine that has been sitting for hours, giving enough time for the oil that can leave the engine to leave it.

To me it dosen't make sense to say wait 2 minutes, or wait 15 minutes (as Haynes says), or even 30 minutes before checking the oil after the engine has been running. I might run 20w-50 and someone else might run 10w-40. I might have an oil cooler he might not. I might be dealing with a 100 degree day and he might be in the 70's. Maybe some of my oil passages are built up a bit with laquer while his are not. All of this can change how much and how fast the oil can flow out of the engine as jrwb and I have just made examples of.

 

If you don't trust the dipstick readings, you can always drain it in a big tub, then filter it into quarts. If you get 8 that's good, because the filter has one. Pour it back in, then read your dipstick. It's a lot of work. Point is, try some of the suggestions above.

 

If you carefully view and read the extract kindly provided above by GGG, it is apparent that both checks are the same or very close. The markings are the same, it is only a matter of what triggers the addition of oil. The "knurled area" is generally 1 litre or so. As the hash mark is in the middle that would be a half litre. Not enough to worry about.

 

LOL. But how do you measure the amount that is now filling your sleeve from when you removed the bung?

Or am I just unlucky?

(as per everyone else, my preference is for a cold check first thing in the morning, after a long hot run, my dipstick can show a zero reading for quite a while).

 

If your really good, the maximum amount you will need to deduct is 2.3 oz's

 

I've been working on cars ECT for 25 plus years so here is a quick thought.

On a cold engine it should read full after its been sitting for hours at least within the hash marks. If you are checking a hot engine Ts beat to wait about 20 min to drain back.

Honestly they hold almost 9 qts of oil and even at 2 qts low you still have more oil than 90 % of the cars an the road lol.