Accuracy of dipstick

[Sandspider]

Hi all.

I recently did my first oil change, and I went from 10W40 semi synthetic to 5W40 fully synth. With the old stuff, oil consumption was very low, maybe a litre every 5,000 miles. But with the new stuff, either it's burning it a lot quicker, or it's leaking out somewhere. (I wouldn't have thought it would leak more when running as the viscousity would be the same at operating temp, and I can't see any oil on the road or my drive).

In any case, I checked the oil level tonight after a 30 mile drive, and according to the dipstick the oil level is below minimum. (It was at max about 500 miles ago). But the oil level warning light isn't on in the car, nor is the oil pressure light (assuming they work of course! Oil pressure light definitely comes on when ignition is first turned on). Oil pressure is normal (5 bar under acceleration, about 4 bar at warm idle) and there are no odd noises from the engine, so is it possible that my dipstick is just inaccurate? I fail to see how it could be, but I also fail to see how everything else could be normal if oil level is really that low.

Many thanks for any thoughts / suggestions, and I will check oil level again when the car has stood for an hour or so.

Giles

 

[Diver944]

First of all make sure you are dead flat when doing the measuring as these cars seem very sensitive to gradient and can give widely different readings.

My own cars illuminate the low level warning when the oil gets half way between max and minimum, so I would suggest that maybe your sender in the sump is broken.

Max to minimum on the dipstick is 1.5 litres so if you really have used that much I think you have a problem. I'm hoping you filled it on a slope and are now measuring it on the level

 

[nick3814]

I always measure mine after shes sat all night. I find that when she's been warm and has cooled a bit from running the measure is a good bit less then when cold as if there must be a good bit of oil that is slow to work its way back to the sump depending on which part of the engine its coming from if you see what I mean.

 

[Sandspider]

Thanks both.

I filled it on the flat, though in retrospect it was more like 800 or 1000 miles ago. I measured it after the run on the flat, and it was very low, but it had only had a minute or two to drain then. I just measured it again, with the car tilted slightly nose high (30 mins or so drainage time), and the level was higher but still below minimum. Will try again in the morning (thanks Nick, hope that helps!). I can also check the sump washer and oil filter for leaks, but as mentioned, there's nothing on the drive. Out of interest, with the back lower than the front, presumably the reading from the dipstick will be slightly higher than the true reading, as the dipstick goes into the sump towards the back of it...?

Incidentally Paul, is 1.5L max to min for S2s? I thought I read somewhere that it was 1L for Luxes, but I might have been dreaming!

And finally, just to check, when I say oil pressure light I mean the red light at the bottom of the oil pressure gage, the bottom red sector of the dial - where should I be looking for the oil level light? (Assuming Luxes have them...)

Looks like I may be adding something else to the list of bits to fix, along with driver's side speaker working intermittently, the odd rumbling noise from the back, and a strange noise from the right front wheel... :s

 

[Diver944]

ORIGINAL: Sandspider

Incidentally Paul, is 1.5L max to min for S2s? I thought I read somewhere that it was 1L for Luxes, but I might have been dreaming!

Ah, you got me there - I've never had a Lux. Though my manual for '89 cars includes Turbos and Luxes and it does state min to max is 1.5L

(Just remembered though that the 1989 Lux was a 2.7 and not a 2.5 like yours)

 

[appletonn]

According to my little official technical specs book, for models up to '87 the difference between min & max on the dipstick was "approx 1 litre" whilst post '88 models it was "approx 1.5 litres".

I should state that the tech booklet covers 944S, S2 & Turbo models, NOT Lux versions, but I would have thought that the S model would have been the same despite the 16V head?

 

[zcacogp]

You NEED to measure the oil cold, and on the level. If you have driven it, leave it for a GOOD couple of hours to get an accurate reading. When in use, the oil is whisked up into the engine and sits around the head and passages. It takes quite a while for it all to drip back down into the sump.

Changing a thicker oil for a thinner one is quite often a cause of problems. Ditto going from a semi to a fully-synth. Why didn't you keep going with the 10W40 semi? (It would be cheaper and you'd avoid problems ... and you would be less likely to use it up, and it is ideally suited for your engine.)

If you really are getting through it that quickly then you must be leaking. You couldn't burn oil at that rate without knowing about it. You'd be driving around with all your lights on permanently, wondering why there is such thick (and peculiarly blue) fog when the weather forecast was for bright sunshine ...

One other thing; I have found that the oil quantity in the sump does not have a linear relationship with the displayed oil level on the dipstick. As in, if you add 500cc of oil to the engine when it is low on the dipstick, it increases the level slightly. If you add another 500cc of oil when it is high on the dipstick then it can increase the level quite dramatically.

Oh, and those oil level sensors always seem to give problems. Dipstick is much more reliable.


Oli.

 

[Sandspider]

ORIGINAL: appletonn

According to my little official technical specs book, for models up to '87 the difference between min & max on the dipstick was "approx 1 litre" whilst post '88 models it was "approx 1.5 litres".

I should state that the tech booklet covers 944S, S2 & Turbo models, NOT Lux versions, but I would have thought that the S model would have been the same despite the 16V head?

Thanks Nick.

Yes, I fished out my manual and the difference between max and min was indeed quoted as 1 litre.

 

[Sandspider]

ORIGINAL: zcacogp

You NEED to measure the oil cold, and on the level. If you have driven it, leave it for a GOOD couple of hours to get an accurate reading. When in use, the oil is whisked up into the engine and sits around the head and passages. It takes quite a while for it all to drip back down into the sump.

Changing a thicker oil for a thinner one is quite often a cause of problems. Ditto going from a semi to a fully-synth. Why didn't you keep going with the 10W40 semi? (It would be cheaper and you'd avoid problems ... and you would be less likely to use it up, and it is ideally suited for your engine.)

If you really are getting through it that quickly then you must be leaking. You couldn't burn oil at that rate without knowing about it. You'd be driving around with all your lights on permanently, wondering why there is such thick (and peculiarly blue) fog when the weather forecast was for bright sunshine ...

One other thing; I have found that the oil quantity in the sump does not have a linear relationship with the displayed oil level on the dipstick. As in, if you add 500cc of oil to the engine when it is low on the dipstick, it increases the level slightly. If you add another 500cc of oil when it is high on the dipstick then it can increase the level quite dramatically.

Oh, and those oil level sensors always seem to give problems. Dipstick is much more reliable.


Oli.

Thanks Oli.

I used to leave it 10 mins or so after driving and found that measuring the oil then or 2 hours later made little difference. (Forgot to check oil this morning to compare with 2 hours leaving time but will do so tonight). I would have thought the slightly thinner when cold (5w) oil would drip back to the sump slightly more quickly than my old 10W oil...

I changed from semi synth to synth as I assumed that fully synthetic oil had to be better, due to longer life of oil molecules, less wear on engine etc. (And also as I had some 5w40 fully synth lying around from a previous car [&:]) The oil in question is mobil and it's apparently "formulated for a higher mileage engine" - though my Lux has only(!) done around 80,000. I also thought that the change from 5w40 to 10w40 wouldn't have made much difference, as the warm viscousity would be the same, so I can't see why the engine would use that much more of it. (It's certainly not coming out in my exhaust - that's no different to how it was with 10w40).

Upon further reading of my manual it would appear that I don't have an oil level sensor, and that my oil pressure warning light (the glowing oil can) doesn't work! (I only have the glowing light at the base of the oil pressure scale when the ignition goes on). In any case, looks like I need to get some more oil in there and probably go back to 10w40 semi synth!

Cheers for all the help.

Giles

 

[zcacogp]

Giles,

The "Which oil should I use" question comes up on here often, and there is no single answer. Some people seem intent on spending lots of money on the most expensive synth oil out there (Mobil 1, Silkolene, Royal Purple etc etc etc) on the basis that it is good stuff therefore should be used in preference to anything else.

The simple fact is that oil tech has moved on a LOT in the last 20 years, and the engines we have in our 944's is designed around 20-year-old oil tech. They work perfectly well on more 'basic' modern oils (indeed, the manuals speak of using single-grade mineral oils - which are so primative they are almost unobtainable now.)

I always maintain that the more important factor in tribology is not the quality or grade of the oil but how often it is changed. I strongly favour (and continue to use) a good but middle-of-the-road spec oil like a 10W40 semi, and change it every 5000 miles on the dot. If I could, I'd change it more often rather than going up a grade or two, but time doesn't permit. (If I could, I'd stick my own personal oilwell under the bonnet, run oil through the engine once and dump it immediately afterwards, but this is also impractical!)

As everyone says, you pays your money and takes your choice. 10W40 semi is a commonly-available grade, and I can get some good stuff very cheaply from GM, so that goes in my S2.

One last point. Oil suppliers have a vested interest in making money, and they make money by selling expensive oil. A politician will never give an unbiased answer when asked which party you should vote for, and an oil supplier will never give an unbiased answer when asked which oil you should buy.


Oli.

 

[944 man]

A dipstick cant really be 'inaccurate', because its a stick sticking into the oil. Where the mark is, is always where the oil is. It could only mislead you if it were bent, but that isnt possible. Max and Min marks can be misleading on some vehicles, with the entire range only covering a relatively small percentage of the vehicles oil capacity, but a dipstick remains foolproof. The oil level warning on a series two is far from foolproof of course, but it isnt intended to replace dipping the sump.

Simon

 

[Diver944]

ORIGINAL: appletonn

According to my little official technical specs book, for models up to '87 the difference between min & max on the dipstick was "approx 1 litre" whilst post '88 models it was "approx 1.5 litres".

Cheers guys, I didn't know that one so that's my one thing learned today [] I can sleep soundly tonight

Nick what does your book say about the 2.7 16v Turbo mentioned in the other thread []

 

[Sandspider]

I too change my oil more often than recommended - every 5,000 miles or more often if I happen to be at home (where my dad has a supply of 5w40 synthetic!).

Just had a quick graze on Hellfrauds website, and they're offering 5L of own brand 10w40 semi synth for £22. They don't do 5W40 semi, but 5w40 fully synth (own brand again) is only £28 for 5L so the price isn't really that different.

I know I shouldn't mix synth oil with non synthetic, but how about synthetic with semi synthetic? And I assume there's no problem with topping up my car with 10w40 although it's currently got 5W40 on board?

Simon - that's what I thought, but I couldn't see how the dipstick could be accurate if everything else was working. Turns out everything else probably isn't working (oil pressure warning light) though oil pressure still remains healthy.

And Oli - that's why I love this forum. So much unbiased information here, it eases my natural inclination to be cynical about anything I'm told by anyone with a vested interest!

Thanks again,

Giles

 

[pauljmcnulty]

I always maintain that the more important factor in tribology is not the quality or grade of the oil but how often it is changed. I strongly favour (and continue to use) a good but middle-of-the-road spec oil like a 10W40 semi, and change it every 5000 miles on the dot.

Or, at least annually even if you don't do the mileage.

 

[appletonn]

ORIGINAL: Diver944

ORIGINAL: appletonn

According to my little official technical specs book, for models up to '87 the difference between min & max on the dipstick was "approx 1 litre" whilst post '88 models it was "approx 1.5 litres".

Nick what does your book say about the 2.7 16v Turbo mentioned in the other thread []

Something about rocking horses......[8|][]

 

[James_G]

ORIGINAL: Sandspider

I too change my oil more often than recommended - every 5,000 miles or more often if I happen to be at home (where my dad has a supply of 5w40 synthetic!).

Just had a quick graze on Hellfrauds website, and they're offering 5L of own brand 10w40 semi synth for £22. They don't do 5W40 semi, but 5w40 fully synth (own brand again) is only £28 for 5L so the price isn't really that different.

I know I shouldn't mix synth oil with non synthetic, but how about synthetic with semi synthetic? And I assume there's no problem with topping up my car with 10w40 although it's currently got 5W40 on board?

Simon - that's what I thought, but I couldn't see how the dipstick could be accurate if everything else was working. Turns out everything else probably isn't working (oil pressure warning light) though oil pressure still remains healthy.

And Oli - that's why I love this forum. So much unbiased information here, it eases my natural inclination to be cynical about anything I'm told by anyone with a vested interest!

Thanks again,

Giles

Last week when I was in Halfords they were knocking out Mobil 1 S (10w40) for £19.95, but in a brilliantly foolish bit of shop front layout, this wasn't obvious until you were stood at the till, paying. By which time I was far more interested in using the carb cleaner I'd just bought on my ISV valve.

Anyway I use Mobil 1 S and change it every 5000 miles too and to my mind it's a good compromise between cost and (perceived) performance. Alas my other car needs 0W30 and that's stupid money, but BMW insist and who am I to argue.

 

[zcacogp]

If you have a registered company and a VAT number, you can register with Vauxhall for their 'Trade Club'.

While the discounts on Vauhall parts prices are HUGE they are useless (unless you have friends with Vauxhalls), but you can get GM 10W40 semi oil for around £1.20/litre, when bought in 20-litre quantities.

The specs on the side of the tin are high (can't remember what they are, but it was the highest spec available when last I checked, about a year ago), and the prices are very cheap. Same goes for gearbox oil and other consumables like wipers, coolant, screenwash etc etc etc. Just remember to wear some overalls when you go to your local Vauxhall dealer otherwise they get very sniffy about giving you the discount (despite showing them the membership card).


Oli.

 

[944 man]

Id suggest that 0w / 5w / 10w oils arent suitable for a 944 of any flavour. 15w or 20w to 40/50 would be more suitable. I received 20litres of Silkolene 10w-50 Pro-R from a sponsor and whilst its a superb oil and itd have been ideal for my Impreza, its just too thin for a 944.....

 

[Hilux]

Quite often the Mobil 1 is only 4 litres []

I wouldnt use it in my 951 (although I`m sure it shouldnt be an issue as its probably better than oils around the time of its manufacture!!!)but I do a deal now and again and buy a box of 6 x 5L perfectly acceptable 10/40 semi synth oil from my local Partco for some £10 - £11 per 5L

Next time I need some I`ll go to Costco who do Chevron 10/40 semi synth x 25 L drum for just over a £/litre.

They are all properly rated.

What with my Landcruiser taking nearly 10 litres per refill and other cars its a no brainer and I`ve had no issues, no increased consumption, no leaks and no damage or perceptible wear over many cars and miles.

 

[944 man]

ORIGINAL: Sandspider

Simon - that's what I thought, but I couldn't see how the dipstick could be accurate if everything else was working. Turns out everything else probably isn't working (oil pressure warning light) though oil pressure still remains healthy.

Re-reading what Id written, it did seem to be rather facetious: which wasnt intended.

Simon