What does the BR think of the temperature of an oil change?
Most manuals say change hot, as the waste products will remain in suspension and the oil will flow quickly.
Other 'mechanics' advocate a cold change, thus ensuring that all the oil is fully drained into the sump.
I have always drained hot; but is this best?
|
Hi Doc,
Your right in saying that waste products remain in suspension whilst the oil is still hot and that theold oil will flow better.
Leave the car a short while to allow the oil to drain back to the sump, then whilst still relatively hot, drain away!.
So it would seem that hot is better.
Pastyman..
|
|
|
Hot for me - occasionally with a flusher in it. If it's hot it will drain down from the top end fairly quicky.
Try draining a diff when cold - it would takes ages for the thick treacle to dribble out.
Martin
|
|
|
|
IMHO, start draining the oil as soon as poss after stopping the engine and getting the car in position. Then go for lunch or a pint and come back after 20 mins or so, when the real crud (if there is any) in the bottom of the sump will have dribbled out. This means that you should try to make sure the drainhole is at the lowest point. It may be easier to shift the filter when hot too.
|
|
And I always used to take it for an Italian Tune immediately before doing an oil change. My reasoning was that more crud than normal was dispersed into the oil, and would therefore be drained out. May be true or not but if felt right. And take care with hot oil. It can be VERY hot.
|
|
|
|
Warm is the best... hot enough so the oil is free enough to run to the sump but left long enough so the oil has time to let gravity do it's job.
To improve engine quality and life, it is best to change the oil more frequently. For very little cost (oil change inc filter costs me £7 as buy in bulk) this can make your car perform alot better.
For example I change the oil on my mums Peugeot 205 every 5000 miles (not 7 as most people do) It has now done 160,000 miles and still going strong and I put it down to the frequent oil changes (and the fact that it is a peugeot (diesel) of course...)
|
|
|
Warm is the best... hot enough so the oil is free enough to run to the sump but left long enough so the oil has time to let gravity do it's job.
To improve engine quality and life, it is best to change the oil more frequently. For very little cost (oil change inc filter costs me £7 as buy in bulk) this can make your car perform alot better.
For example I change the oil on my mums Peugeot 205 every 5000 miles (not 7 as most people do) It has now done 160,000 miles and still going strong and I put it down to the frequent oil changes (and the fact that it is a peugeot (diesel) of course...)
|
|
|
Below is an answer "straight from the horses(lub-oil-engineer's) mouth"
www.machinerylubrication.com/article_detail.asp?ar...3
with permission to copy; William Birch, "Automotive Oil Changes Made Easy". Machinery Lubrication Magazine. January 2003
There are two methods of performing an oil change. The first is to normalize the engine operating temperature. That requires the engine to idle for a time or a few trips around the neighborhood. Now that the engine is warm, drain the sump and change the filter. The thought behind this is contaminates are suspended in the oil and when the sump is drained, the harmful contaminates drain with the oil.
The second method is to drain the oil when the engine is cool, when a good percentage of the oil has settled into the sump. For a couple of years, I practiced the first method. Both have merit; however, the second method works best for me. With either method, the most important step is to develop a routine that works. The location where the procedure is performed should be reasonably level as most sump bottoms are formed to tilt toward the drain plug.
>>>" .... Draining the oil when the engine is cool (method number two) offers the following benefits: It is not necessary to circle the block a few times or have the engine at high idle for 20 minutes trying to warm the oil; when the engine has been at rest for several hours and the drain plug is removed, the oil is cool and drain flow is more controllable; pressure between the filter and the filter housing has bled off, making filter removal a cleaner process. A cleaner process is generally a quicker process. ....">>>
|
A thought that has often occured to me, in my eagerness to get on with the job, is, does it matter pouring cold oil into a hot engine? Is there a risk of cracking something?
Another oil change point: who, like me, always fills the new filter before refitting, to avoid the engine running for 5 seconds with no pressure?
|
Another oil change point: who, like me, always fills the new filter before refitting, to avoid the engine running for 5 seconds with no pressure?
I remove the fuse to the fuel pump and let the engine die before the change.
After the oil change I can crank over the engine to fill the filter without the bores getting flooded with unburnt fuel.
|
Another oil change point: who, like me, always fills the new filter before refitting, to avoid the engine running for 5 seconds with no pressure?
"I remove the fuse to the fuel pump and let the engine die before the change. After the oil change I can crank over the engine to fill the filter without the bores getting flooded with unburnt fuel."
Are engines with canister filters -- fixed canisters with an inner replaceable filter, as on both my cars -- different in this respect?
|
|
|
|
Doc, Cliff - the answer to this will depend on whether the engine is diesel or petrol, which is less lubricant and more solvent. But decades ago oil companies were selling their product on the point that it stayed on the mating surfaces for a long time, so I feel sure that a good film will persist during a 20-30-minute oil drain.
|
|
|
|
"A thought that has often occured to me, in my eagerness to get on with the job, is, does it matter pouring cold oil into a hot engine? Is there a risk of cracking something?"
I don't think so, the temp difference would be about 60?c, but the oil has a much lower heat capacity than say water. ie, it aborbs the heat slower, and absorbs less thermal energy before being at equilibrium temperature with the block.
|
|
|
|
Your source is correct eMBe and uses a similar logic to mine.
If a car comes in 8.30am for a 9am oil change then great to have it warm and also time to allow it all to drain back to the sump.
However if the car came in the previous evening is it really good sense to run it on cold start fuelling in the workshop to get it hot, and in doing so push all the oil to the top again where you'll have to wait even more time for it to drain back.
Anyway so many cars use semi or fully syn 0/5/10w40 that they drain quite well when cold.
That you do change the oil every 6K or so is more important than the hot or cold drain choice.
M.M
|
Exactly the reason when a car comes in for service the night before, I try to allow the oil to drain overnight.
|
Probably won't make the slightest difference (in engine longevity terms) if the drained oil is hot or cold. You could leave the sump plug out for a year and still not drain all of the oil out. There's going to be at least half a litre of oil trapped in undrainable places.
Going back a few years (to the days of the BMC transverse 1800cc engine) the initial oil fill was about 12 pints, the oil change fill was about 8 pints.
|
I agree but it drains far more effectively (and quicker!) when hot.
|
And another thing...
If the vehicle is sitting on the drive whilst the oil drains out, hide all sets of keys from any other drivers. So they don't jump in, start up, and drive off. Although they won't get far...
rg
|
If the drain plug is out for too long it can let dust in.
I had to do an oil change in one of my bangers in the south of France once, in a campsite. It was a bit windy as the Mistral was blowing hard. Dust and sand all over the place. Anyway that plug went in pretty quickly after the bulk of the oil had come out. (We couldn't postpone it till the wind died down as we were off the following day to Morocco and had no idea where we would have disposed of the oil in Casablanca.)
Extreme example, I know but if your garage floor is as dusty as mine and there is a bit of a gale outside I wouldn't want to leave the drain plug out over night.
|
|
|
|
|
