Stupid oil question

Fey!

Is it risky to mix a mineral oil (15/45) with a semi-synthetic oil (10/40)?

Oil light came on today on my mothers car ('98 BMW e39 520, 103k), and I need to top it up, but I can only get my paws on mineral, wheras I'm pretty sure it's semi-synth that my mechanic used when he serviced it last.

franksm

You can mix away to your heart's content.

The only problem I ever heard with oil (other than using the wrong viscousity/weight of oil) is in converting a car over to fully-synthetic later in its life, when it has been using mineral previously. Seems that the fully-synth can start weeping through the various oil seals (like between the crank and the flywheel).

But mixing different typres of oil ? It's all fine

Lex Luthor

I would have thought it wouldn't be advisable to mix..????

Fey, why is it so hard to get semi-synth? Halfrauds sell it in the green bottles (1l & 5l)

Fey!

I was relying on service stations, but that's for a new thread later on!

Thanks for the replies.

JohnCleary

ANY oil is better than NO oil

I have 10w 40 in my gearbox
And before the (not) so smart asses start raving, it's perfectly fine for the gearbox that it's in, so long as its changed every 30k miles. It makes gear changes much smoother. Only for the DIY'ers though as you'll be under the engine every few months to change it (I just change it every 2nd engine oil run, so about every 12k miles to be safe)

mukki

WTF :eek: oil light came on ???? :eek:


its not like your petrol light, this only happens when the oil is so low that the pump is pullin in air, or the pump is faulty, anyway the engine will die in minutes if you dont turn it off and get it looked at

JohnCleary

Isint the oil light for pressure? Not a good thing! Must have been VERY low or something's up

C_Breeze

Your oil light should NEVER have to come on in a car... especially if it is getting its oil service every 5k miles as it should. Ever heard of checking the dipstick once in a while?? Perfect example as to why I would never buy a car off a "Lady Driver" :rolleyes:

....Anywaaaay, to answer your question you may as well mix the oils as it seems you dont give a crap about the car anyway. And fully synth oil is not hard to find at all.

I always keep 5 litres of oil in my shed as i always buy 2 tanks when i go to purchase oil just to have. Me, personally, I would change the oil filter and fill it up properly with some decent fresh oil

Fey!

It's the yellow "low warning" light that came on, not the red "wtf are you trying to do to me" light.

C Breeze - may I suggest that you fcuk off back under the rock you slithered out from under. If I wanted an answer from a troll, I would have posted in Thunderdome.

EDIT: Oil, water, coolant, tyre pressures et al were checked 2 weeks ago, and all was fine. Car was serviced a 6 weeks previously, or about 3,000 miles ago.

BrianD3

AFAIK semi synths and mineral oils are chemically similar. I'd see no problem with topping up a 10w40 semi synth with a 15w40 mineral. However if the oil light came on as the others have said the oil must have been pretty low and needed more than just a "top up". Therefore you now have a good proportion of 15w40 mineral in there which might not be the best oil for your engine. But on a 9 year old 520 you're probably not all that fussed anyway. edit: I just saw the last post about the yellow oil light so disregard the above bit

As for filling a gearbox with 10w40 engine oil - OK if that 's the oil the gearbox is designed for. But if it's designed for 75w90 or something then the engine oil is way too thin and will not lubricate as it should no matter how often it's changed.

Lex Luthor

I have a 97 523i and in between the 12k mile services, the oil level never drops, not even a mm on the dip stick.

I would get it checked out?

Is it possible this engine could fall into the nikasil bracket?

Biro

Fey! wrote:

It's the yellow "low warning" light that came on, not the red "wtf are you trying to do to me" light.

C Breeze - may I suggest that you fcuk off back under the rock you slithered out from under. If I wanted an answer from a troll, I would have posted in Thunderdome.

EDIT: Oil, water, coolant, tyre pressures et al were checked 2 weeks ago, and all was fine. Car was serviced a 6 weeks previously, or about 3,000 miles ago.

No need to get violent people.
It doesn't matter if the light is yellow or red, it's engine damage time if it comes on at all. I wouldn't mix if I had the option, but as was said above, any oil is better than no oil.
10-40 semi is very common everywhere though, it should be no problem to get some.. but aside from that, there must be a problem if it's burning oil. 3,000 miles in 6 weeks is a nice bit, 30,000 miles a year is above average usage, but it shouldn't have used oil in a week if something isn't wrong.

C_Breeze

Fey! wrote:

It's the yellow "low warning" light that came on, not the red "wtf are you trying to do to me" light.

C Breeze - may I suggest that you fcuk off back under the rock you slithered out from under. If I wanted an answer from a troll, I would have posted in Thunderdome.

EDIT: Oil, water, coolant, tyre pressures et al were checked 2 weeks ago, and all was fine. Car was serviced a 6 weeks previously, or about 3,000 miles ago.

Thats disgraceful, i answered your question and gave my advice only to be told to f*uck off.

Fey!

C-Breeze - read your previous post. If you don't like my response, then report it.

It's very rarely that someone gets under my skin badly enough to evoke a response like that from me. How would you like it if I went on to your thread about the knock in your car and said "why bother trying to fix it? Sure it's obvious from you revving the ar$e of it that you don't give a monkeys about it".

maidhc

Fey! wrote:

EDIT: Oil, water, coolant, tyre pressures et al were checked 2 weeks ago, and all was fine. Car was serviced a 6 weeks previously, or about 3,000 miles ago.

Is there a leak?

Last time I serviced my car I didn't tighten the oil filter enough. It loosened and started to leak oil. Thankfully I spotted my stupidity long before the oil level dropped to dangerous levels, but it goes to show. Scary experience though.

C_Breeze

Fey! wrote:

C-Breeze - read your previous post. If you don't like my response, then report it.

Nah its cool, forget it.

Feel free go to my thread and say that as long as you have a suggestion. As I said, i suggest you change the oil filter and fill it up with fresh oil. - preceisely for the reason that maidhc pointed out.


- Mental note to self: never post in Feys threads again -

Fey!

No sign of a leak. The car is always parked in the same spot, and my father can't see any sign of oil there.

The car has been parked since the light came on, so I got him to check it before he left for work this morning. Also got him to dip the oil to check how low it is. The level is above the minimum on the dipstick.

So the question now is why did the light come on if the oil level is ok.

BrianD3

This thread says to me that every car should have an electronic dipstick like Renault have been fitting to many of their cars for years. Everytime you start the car you get a reading of how much oil you have. On the older cars it's a gauge, on newer ones there's a display which shows a series of "O" characters and an "oil ok" message.

Gerry

Fey, I had a tough time trying to find semi synth late at night also. Maxol have it on their pricelist, but don't seem to bother stocking it. And they look at you like you have two heads if you ask them any questions. Eventually had to pay through the nose for a litre of mobil 1 at applegreen.
Anyway - if the oil is near min on the dipstick, then the oil level is not ok, and so its perfectly reasonable for the light to come on. How low is it exactly? Surely its better for the light to come on before the level passes below the min mark?
When topping it up, you may need to add a litre to bring it to the max, as someone else pointed out, thats a significant portion of mineral oil in the engine. So, either keep looking for semi synth, or change the oil if you top it up with mineral.

Lex Luthor

Fey! wrote:

So the question now is why did the light come on if the oil level is ok.

Fey, I know someone with a '02 E46 and his oil light came on when the oil was reading just above the min mark on the dipstick.

Faulty sensor....€80 for the part from Keanes. Drained the oil. Removed & replaced. New oil & filter.

Just make sure the connector on the sensor is the right one before you drain the oil. They gave hom the wrong one first and he had to re-fill the oil and drive back up and get the proper one

Fey!

Thanks for that, folks. Haven't put in the oil yet - the car is still parked, and will remain that way until I get semi-synth.

Gerry - better the light come on than the oil run out!!

mukki

Fey! wrote:

The car has been parked since the light came on, so I got him to check it before he left for work this morning. Also got him to dip the oil to check how low it is. The level is above the minimum on the dipstick.

So the question now is why did the light come on if the oil level is ok.

if there is any oil in it then it must be the oil pump's relief valve is jammed open, and when the oils gets warm it thins so that more can get through the relief valve and the pressure gets too low so tirggers the light

did the light go out if she revved it up, if so, get it looked at asap

Fey!

Got my hands on the car myself this morning. The oil level was fine without topping it up, and the light is no longer on. Could have been a sensor snafu. I'll just have to keep an eye on it.

Will try to get it to a diagnostic.

Thanks for the help/advice, and apologies for my earlier cantankerousness!