# Do you check your oil hot or cold?



## Perfezione (Nov 23, 2006)

Seems a bit of a taboo subject this. 

I have always checked my oil at normal operating temperature about 5-10 mins after a journey. As all my previous owners manuals have advised me to do this. (so i guess i'd class this as hot) 

However many people say it should be done cold. Ie, after being left over night. 

I'll continue to follow my manual. 

But what do you do???


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## Ninja59 (Feb 17, 2009)

depends on engine i always do both tbh  my manual says either but i find cold much easier.


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## bigmc (Mar 22, 2010)

I check mine when it's cold, on a level surface and been sat for a good few hours. It makes no difference really but you always fill it cold so check it cold.


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## Derekh929 (Aug 28, 2011)

Cold for me always


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## Damien89 (May 13, 2007)

I check mine 5 mins after i come home from a drive, i need my oil to be at the right level when the engine is running (hot) not when the engine is cold.


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## bigmc (Mar 22, 2010)

5 minutes isn't long enough to drain all the galleries back to the sump. The coefficient of expansion is minimal - approx 0.0006/°C


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## The Cueball (Feb 8, 2007)

I do both..

:thumb:


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## Damien89 (May 13, 2007)

bigmc said:


> 5 minutes isn't long enough to drain all the galleries back to the sump. The coefficient of expansion is minimal - approx 0.0006/°C


or maybe 10 mins, point is check the oil when its hot, i.e all the time the oil is being used is hot so its useless to check it cold.


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## bigmc (Mar 22, 2010)

Damien89 said:


> or maybe 10 mins, point is check the oil when its hot, i.e all the time the oil is being used is hot so its useless to check it cold.


Do you not have oil in the car when it's cold then?? Not teaching you to suck eggs but oil isn't just a lubricant, it's also for corrosion resistance and heat transfer.


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## Damien89 (May 13, 2007)

bigmc said:


> Do you not have oil in the car when it's cold then?? Not teaching you to suck eggs but oil isn't just a lubricant, it's also for corrosion resistance and heat transfer.


Yeah i know but when oil gets hot the dipstick will show a bit lower level then when cold.


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## Perfezione (Nov 23, 2006)

Ok, i'll throw a senario out there. 

Recently changed the oil in my mum's Mx-5. Renewed with exactly 4.5l of oil as stated by the manual. The oil was dropped when warm as per usual. 

The let the car run for 10 mins at operating temp and then shut off and left for 5 mins (as per manual) and took a reading. Read bang on max level. 

The next day after being left to cool over night i take a reading and its reading over the max. ie, overfull. 

Surly the manufacturer is going to state the best method for your car (which for some may be cold) 

But it seems taking a reading when cold on the mx-5 does not give an accurate reading, as i measured how much i drained and how much i refilled. A warm reading is consistant with this, yet a cold is not. 

This is why i'm going to just do what the manual says and not follow any hard and fast rules in future.


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## shane_ctr (Dec 17, 2006)

Always test engine oil when cold most accurate reading


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## Perfezione (Nov 23, 2006)

shane_ctr said:


> Always test engine oil when cold most accurate reading


For you car?

Because it doesn't seem to be for mine.


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## Damien89 (May 13, 2007)

alex163 said:


> Ok, i'll throw a senario out there.
> 
> Recently changed the oil in my mum's Mx-5. Renewed with exactly 4.5l of oil as stated by the manual. The oil was dropped when warm as per usual.
> 
> ...


Because when oil gets hot it gets thinner thus giving you the proper reading.
Imagine checking your oil when cold and its at the bottom of the dipstick, one would think that it is ok, but when the same amount of oil is checked hot you find that the dipstick isnt even touching the oil.


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## bigmc (Mar 22, 2010)

Engine oil expands when it's hot not the other way around.


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## Perfezione (Nov 23, 2006)

Yea, i know exactly what you car saying. 

I guess the dipstick will be calibrated to how your manual states to take the reading.


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## spursfan (Aug 4, 2009)

Always cold, gives a true reading..
If you check it hot you get an incorrect reading as oil is still in some galleries etc..
By Overfilling your engine with oil you can cause the oil to foam and get sucked up into the crankcase ventilation system. This is not a good thing. A clogged CV system will lead to buildup of pressure and that can blow out seals and cause severe oil leaks, especially on older engines A severe leak on a long drive can drain enough oil from your engine for damage to occur. 

Kev


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## Damien89 (May 13, 2007)

bigmc said:


> Engine oil expands when it's hot not the other way around.


So why is it better to drain the oil when hot?
And why do we need to use higher viscosity oil in 
Summer than in winter? ( winter 5/30, in summer 10/40 due to higher temps)


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## bigmc (Mar 22, 2010)

Damien89 said:


> So why is it better to drain the oil when hot?
> And why do we need to use higher viscosity oil in
> Summer than in winter? ( winter 5/30, in summer 10/40 due to higher temps)


Because it flows better when hot. The summer/winter viscosity is for better hot and cold flow according to climate.


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## spursfan (Aug 4, 2009)

Damien89 said:


> So why is it better to drain the oil when hot?
> And why do we need to use higher viscosity oil in
> Summer than in winter? ( winter 5/30, in summer 10/40 due to higher temps)


Read my previous post, or look on the web, you will find that Bigmc is correct.
Alternatively, ask a good mechanic, he will say exactly the same..


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## Perfezione (Nov 23, 2006)

spursfan said:


> Always cold, gives a true reading..
> If you check it hot you get an incorrect reading as oil is still in some galleries etc..
> By Overfilling your engine with oil you can cause the oil to foam and get sucked up into the crankcase ventilation system. This is not a good thing. A clogged CV system will lead to buildup of pressure and that can blow out seals and cause severe oil leaks, especially on older engines A severe leak on a long drive can drain enough oil from your engine for damage to occur.
> 
> Kev


But it doesn't "always" give a true reading.

It didn't in my case.


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## spursfan (Aug 4, 2009)

alex163 said:


> But it doesn't "always" give a true reading.
> 
> It didn't in my case.


Cant really say much more, just hope you dont ruin the engine.
Ask your local dealer for your car, they will be able to tell you what should be done and the correct way to do it.


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## David Proctor (Mar 6, 2011)

Always cold.


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## Perfezione (Nov 23, 2006)

i hope i don't ruin the engines either. 

I'm presuming, the local dealers would state the same as the owners manuals, and that Mazda and Mercedes haven't miss printed their manuals and they should be checked at normal operating temp 5mins after shutting off.


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## PaulTheo (Sep 26, 2010)

Hot or cold no different as long as it has stood for at least 5 to 10 minutes. I can't check mine except on the onboard computer there is not even a dip stick fitted to my Audi!! Which took a bit of getting used to.


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## -Kev- (Oct 30, 2007)

cold - checking when its hot and most of the oil is everywhere apart from the sump, where the dipstick takes its reading from, is going to give false info


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## ianFRST (Sep 19, 2006)

cold!

if you have just filled your engine with oil, keep checking the dipstick, then run it up for 30 seconds, and check again


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## Dixondmn (Oct 12, 2007)

Damien89 said:


> I check mine 5 mins after i come home from a drive, i need my oil to be at the right level when the engine is running (hot) not when the engine is cold.


not having a pop, but thats like saying, i check my tyre pressure when they are warm because i want them at the correct psi when in use.

Always check oil cold. (and tyres)


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## Captain Pugwash (Mar 23, 2011)

always check mine when its cold, it was what i was taught...might have changed for more modern cars I suppose, but dont have one of those


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## andy monty (Dec 29, 2007)

Damien89 said:


> Yeah i know but when oil gets hot the dipstick will show a bit lower level then when cold.


eh? surely it will be at a higher level when hot as Oil expands when heated


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## bidderman1969 (Oct 20, 2006)

Damien89 said:


> Yeah i know but when oil gets hot the dipstick will show a bit lower level then when cold.


not really, as alot of the oil is still all around the engine


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## getthewheelsinl (Apr 6, 2010)

Did you change oil filter & the same time? If the 4.5l was including oil filter change then sounds as if you didn't completely drain oil but still put in the quoted 4.5l in.


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## srhutch (Aug 2, 2009)

The handbook for my car says to check one minute after switching off the engine from hot.

This is what I'm going to follow.


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## Grizzle (Jul 12, 2006)

Cold every weekend along with coolant and tyre pressures (yes i am that fecking sad lol)


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## Perfezione (Nov 23, 2006)

getthewheelsinl said:


> Did you change oil filter & the same time? If the 4.5l was including oil filter change then sounds as if you didn't completely drain oil but still put in the quoted 4.5l in.


Yep, changed the filter at the same time. Got 4.5l out and put 4.5l in. Measured it.


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## Damien89 (May 13, 2007)

dixon75 said:


> not having a pop, but thats like saying, i check my tyre pressure when they are warm because i want them at the correct psi when in use.
> 
> Always check oil cold. (and tyres)


Thats when i check my tyres(hot)


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## hoikey (Mar 9, 2011)

Damien89 said:


> Thats when i check my tyres(hot)


Do you really? Remind me never to bring a car to you lol


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## PugIain (Jun 28, 2006)

Cold.The oil will still be coming back to the sump from around the bits its protecting otherwise.


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## Damien89 (May 13, 2007)

PugIain said:


> Cold.The oil will still be coming back to the sump from around the bits its protecting otherwise.


So how much time you think the oil takes to drain in the sump?


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## PugIain (Jun 28, 2006)

Damien89 said:


> So how much time you think the oil takes to drain in the sump?


A long time.
I said.And Im bigger than you.


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## Dixondmn (Oct 12, 2007)

Damien89 said:


> Thats when i check my tyres(hot)


again, just some friendly advice, but you're in danger of over inflating your tyres if you check and top up when the car has been driven.
costing your £££ in tyre wear.

just my 2p worth.


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## Richf (Apr 26, 2008)

Damien89 said:


> I check mine 5 mins after i come home from a drive, *i need my oil to be at the right level when the engine is running* (hot) not when the engine is cold.


In that case surely you should check when the engine is running 

Wow some people's logic , you "should" always check when cold or after the engine has cooled a little after use and the oil has had time to settle in the sump, if the engine is hot you should allow it to cool before topping up since you should not put cold oil into a hot engine, if you really have to you should do it slowly and just trickle it in

All pretty much common sense

The reason you warm the engine a little before draining the oil is as mentioned it will be thinner and flow out faster , hopefully dragging more of the containments at the bottom of the sump out, again you shouldnt drain the oil out of a hot engine


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## SteveyG (Apr 1, 2007)

Damien89 said:


> I check mine 5 mins after i come home from a drive, i need my oil to be at the right level when the engine is running (hot) not when the engine is cold.


The levels on the dipstick are designed to be representative when the engine is cold/not running.


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## nick_mcuk (Jan 4, 2008)

SteveyG said:


> The levels on the dipstick are designed to be representative when the engine is cold/not running.


Unless you own an old Porka 911 where you have to have it upto running temp and with the engine running to check the oil level.

On normal cars though I normally check when it's cold or the car has been standing for a good 30 mins.

Sent from my iPhone using Tapatalk


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## DampDog (Apr 16, 2011)

Just had a little look in my handbook and it recommends checking when hot, about 10 mins after turning off. Which is what I've always done anyway 10-20 mins after stopping.

Many years ago I had a gf who who brimmed her triumph toledo to the top of the filler neck. She thought she had a flat battery because it wouldn't turn over. At least the engine bay was never gonna rust, it all but blew the rocker cover off.


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## Perfezione (Nov 23, 2006)

SteveyG said:


> The levels on the dipstick are designed to be representative when the engine is cold/not running.


Nither of mine are


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## Perfezione (Nov 23, 2006)

DampDog said:


> Just had a little look in my handbook and it recommends checking when hot, about 10 mins after turning off. Which is what I've always done anyway 10-20 mins after stopping.
> 
> Many years ago I had a gf who who brimmed he triumph toledo to the top of the filler neck. She thought she had a flat battery because it wouldn't turn over. At least the engine bay was never gonna rust, it all but blew the rocker cover off.


Think most will find this.

i've not had a car thats said it shouldnt be checked at operating temp. But seems all those manufacturers are wrong.


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## DampDog (Apr 16, 2011)

You got a 911?

Aren't they supposed to be checked hot and running?


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## McClane (Dec 9, 2010)

Something tells me this discussions is equivalent to "should i try to drive my car on the left of the road regardless of what country I'm in?"

Do it cold if the book says so, hot otherwise. Seems pointless applying general logic across all the different types and exceptions surely?


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## DampDog (Apr 16, 2011)

Lol... I'm just thinking that myself, it's horses for courses. With all the various maunfacurers and cars on the road there is no "right way". 

I'll get me coat..


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## The Cueball (Feb 8, 2007)

McClane said:


> Something tells me this discussions is equivalent to "should i try to drive my car on the left of the road regardless of what country I'm in?"
> 
> Do it cold if the book says so, hot otherwise. Seems pointless applying general logic across all the different types and exceptions surely?


or if you have a RX8, then fill it up all the time! :lol:

(only kidding) 

:thumb:


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## bigmc (Mar 22, 2010)

Damien89 said:


> Thats when i check my tyres(hot)


Are you really that stupid or are you just trolling the boards??


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## Perfezione (Nov 23, 2006)

DampDog said:


> You got a 911?
> 
> Aren't they supposed to be checked hot and running?


No, i wish mate. But i believe they are.

Manuals from Ford, Honda, SAAB (GM), BMW, Mazda & Mercedes have all said to check at operating temp five mins after shutting off.

I just wonder how many people follow the manual? Rather than just saying "i do it cold because i always have"

Because from my experience not following the manual gives an inaccurate reading.


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## Richf (Apr 26, 2008)

alex163 said:


> Think most will find this.
> 
> i've not had a car thats said it shouldnt be checked at operating temp. But seems all those manufacturers are wrong.


Very few handbooks will tell you not to drive after 15 pints of Stella so that must be ok as well:thumb:


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## Richf (Apr 26, 2008)

Many newer cars of course dont have a dipstick , (Mercedes for example) and they only have an oil sensor which ensures the level is over minimum (I always run my cars just under max personally), the dashboard activated system does indeed need the oil hot and will just tell you if the level is ok (ie over the minimum which imo is *not* ok) or if it needs topping up (ie under the minimum)which in most cases requires at least 1 litre of oil added, one litre is usually the difference between minimum and max on most cars dipsticks , I have never ever run a car that low myself

Manufacturers found they sold a lot more oil this way and probably quite a few more engines, its not for the customers benefit

In many cases you can buy a dipstick , the dealers use certainly use them and there is a tube but they wont like selling you one

IF the car has a dipstick then in by far the majority of cases checking when cold is the way to go


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## Pezza4u (Jun 7, 2007)

I always check mine when cold and always will. How can you get an accurate reading if there is still oil around the engine!



Grizzle said:


> Cold every weekend along with coolant and tyre pressures (yes i am that fecking sad lol)


Same as me or at least every fortnight and it's not sad at all, it's wise to check these things. Shame more people don't and then you wouldn't have so many death traps on the road. That's from a tyre perspective as some people will run them down to the canvas!


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## bigmc (Mar 22, 2010)

I check mine weekly without fail, all lights, coolant, oil, brakes & fluid, tyres and washer fluid.


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## Grizzle (Jul 12, 2006)

I think 99% of us on here do weekly or fortnightly checks and do it as part of a weekly/fortnightly wash routine i know i do anyway, most are visual checks and it takes what 15-20mins maximum to do and saves a whole load of hassle.


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## DampDog (Apr 16, 2011)

Dunno if it's anything to do with age, but I grew up with cars that demanded weekly attention not the modern miracles we drive today that only need serviceing when they tell you. When was the last time you saw a grease nipple?

I do fluids, lights and tyres once a week. It's just habbit


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## dew1911 (Jun 9, 2009)

I always check mine cold, done it with every car I've had and the works vans, found when hot they tend to over read (understandable as hot oil expands), never had a problem with it, on the Transit 3/4 when cold reads dead on max when hot. Tyres get visual checks daily and tread/pressure if I think they need it or once a week, and lights simply checked as I walk round, or for brake lights when I'm reversing towards a window.

My car just gets weekly but it only does about 40 miles a week.


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## spursfan (Aug 4, 2009)

DampDog said:


> Dunno if it's anything to do with age, but I grew up with cars that demanded weekly attention not the modern miracles we drive today that only need serviceing when they tell you. When was the last time you saw a grease nipple?
> 
> I do fluids, lights and tyres once a week. It's just habbit


Last night!! bit kinky i know...


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## msb (Dec 20, 2009)

not a scientist but thought pretty much all fliuds expand by some amount when heated/hot so surely the best consistant way is checking when cold, thats what i've done for the last 20 years + of driving since getting my first car,and also the guy who's filled his mx5 with 4.5 litres of oil has over filled by half a litre as handbook says 4 litres for oil change incl filter


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## kings.. (Aug 28, 2007)

i always start the car let it run for thirty seconds then sit for 3mins then I check it.


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## msb (Dec 20, 2009)

kings.. said:


> i always start the car let it run for thirty seconds then sit for 3mins then I check it.


WHY?????

All you've done by doing that is push cold oil round that then will take an age to settle and probably give an incorrect reading when the levels checked, not to mention the engine wear


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## Trip tdi (Sep 3, 2008)

I check mine cold, but i do have a problem starting my car at present when cold, not to sure if its the weather or the glow plugs need changing.


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## msb (Dec 20, 2009)

Trip tdi said:


> I check mine cold, but i do have a problem starting my car at present when cold, not to sure if its the weather or the glow plugs need changing.


is starting to get to that time where diesels play up, battery went on the sister focus tdci yesterday, could also be a weak battery on yours:thumb:


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## Jace (Oct 26, 2005)

I check it when cold, I also check tyres when cold too.

Before I perform the weekly wash, I check it all whilst stood in the garage.


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## Perfezione (Nov 23, 2006)

msb said:


> not a scientist but thought pretty much all fliuds expand by some amount when heated/hot so surely the best consistant way is checking when cold, thats what i've done for the last 20 years + of driving since getting my first car,and also the guy who's filled his mx5 with 4.5 litres of oil has over filled by half a litre as handbook says 4 litres for oil change incl filter


My handbook doesn't

4.55l for oil and filter change in a 2.0l mk3 :thumb:


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## kings.. (Aug 28, 2007)

msb said:


> WHY?????
> 
> All you've done by doing that is push cold oil round that then will take an age to settle and probably give an incorrect reading when the levels checked, not to mention the engine wear


I think you should have a look at a few modern car hand books! historically yes it was done on a cold engine on level ground etc etc now things have changed!


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## gordonpuk (Mar 14, 2010)

I always thought that we're told to check these things before setting out on a journey
not after getting there.
Can't see many people going for a drive, coming back home having a cuppa and
then going out to check the levels before the real journey.
So, as you can guess, it's cold for me.


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## Trip tdi (Sep 3, 2008)

I remember this thread its a good one, its been digged out again.


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## Dixondmn (Oct 12, 2007)

kings.. said:


> I think you should have a look at a few modern car hand books! historically yes it was done on a cold engine on level ground etc etc now things have changed!


Do you have any examples?

Its clear we have a divide amongst the DW community on this one, but there seems to be an abundance of 'common sense' justification for checking when cold, but I've yet to see any mechanical rationale for checking 'modern' oil in 'modern' engines whether its either warm or cold.


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## msb (Dec 20, 2009)

kings.. said:


> I think you should have a look at a few modern car hand books! historically yes it was done on a cold engine on level ground etc etc now things have changed!


so your handbook says warm unlevel ground then
Not saying you can't do it when warm(but the engine needs to be left after switch off for a good 5 mins + )but generally imo when cold is the accepted,accurate way


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