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oil change

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sp53

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When changing oil do you people change the oil when the engine is cold or hot? I do not know if it actually makes a difference; however, it seems that the engine rattles just a fuzz for that first moment if you do it cold. I use to work with this wise old German mechanic who felt that when changing oil it would be best to do it cold, and to pour a clean can of oil through the engine by leaving the drain plug out for the first quart. I guess he figured why put the dirty oil back up in the engine and running a flusher would get out more junk. Then my other buddy maintains that you want the oil hot, so it will run right out. Any comments will be appreciated.
George
 
I always change my oil hot. I figure that when it is hot, it will flow easier, letting you get more dirty oil out of the engine. Also, when hot maybe more dirt is suspended in the oil instead of stuck to the inside of the engine.

Matt
 
George,

This is definitly one of those topics that are personal expeiriance & preferance.
I see the value of changing the cold ,simply because it has mostly drained in to the pan. This is good for warmer weather , but cold oil does flow really , really slow & too much cold oil may remain in the pan.

On the other hand, warm oil does flow easier & it is important not to create a dry startup condition. Running the motor to warm the oil leaves a coating on the internal parts , so on start up the delay on the new oil delivery through the filter & block will not be harmfull.. Even though I fill the oil filter with oil before installing , it take time for pressure to build, enough time to cause wear.

I guess it's understood not to let the oil get so dirty that any remaining oil could be so bad as to contaminate the new stuff.
 
Hello all,
I also go for the hot, as it flows easily and i leave it for some time while I do other jobs so as to get as much out as possible. On start up I crank the engine without ignition until I have oil pressure then start it to check for leaks.

Alec
 
Hot. After a run preferably, while all the grunge is still suspended and hasn't settled.

How else can you burn your fingers on the plug when removing it, and then drop it into a pan of horrible used hot engine oil?

A cold change is easier, but leaves the heavier sludge behind....
 
I agree with everyone else, a hot change is the way to go (maybe let the car cool a little so that you don't burn yourself).

Thinner oil drains better and any contaminents are more likely in suspension and will be drained off with it.

Even if it were desireable to do so, it's virtually impossible to get absolutely *all* oil out of the system. Heck, the oil cooler and hoses on my car probably trap almost a quart of oil that won't be easily drained. Regular changes with good quality oil are the best we can do and likely more than adequate.

The magnetic oil drain plug is a good idea, IMHO.

Cheers!
 
Sorry guys, Im going for the dissention vote. There are too many exhaust parts under a car to be working on hot. Most people here seem to think the hot oil would pick up more crud and flush it out. My thinking is the oil filter will pick this stuff out, so your not gaining anything by changing it hot. I always open the drain plug first, leave it open for an hour or more to drain. Most of your dripping is done by that time. Yeah, it takes longer, but if you are like me, your doing 15 other things to your car at the same time anyway. $0.02 /ubbthreads/images/graemlins/grin.gif
 
I drain mine cold too. Same reasoning as Mailbox. Sometimes I let it drain overnight.

When it come time to start it up again, I remove the plugs - it's time to check the gap - and I crank over the engine about 50 times with my hand crank (TR3A) and then I crank it about 50 cranks on the starter to build up the pressure. Then I re-insert the plugs and it's ready to start. Then I check for leakage around the filter seal, etc.
 
I do it hot... on a TR3 (or 4) the exhaust is a long ways off so that is not a concern. I get the plug out with a long extension then let it drain quite awhile. For really thorough drain you can jack up the right front corner a bit.

I don't do any special start-up procedures figuring the lack of lubrication is no more than what occurs in an engine that has sat overnight.

Guess it's like asking whether the evening meal at your house is dinner or supper.
 
I'll go with warmed up oil. I've never given it much thought, it is the way I've always done it and seen it done. Detergent oil tends to carry many of the contaminants cause by combustion in suspension, which is why the oil takes on that black color over time. I think they remain in suspension regardless of the oil temperature.

Safety Fast,
Dave
 
Clearly you guys have not ever made a living as a mechanic. Oil gets changed cold, warm or hot, depending on how it happens to be when the job comes in. The drain plug stays out until the flow is mostly gone. You get paid about ten minutes to do the entire job, including getting the job, finding the car and getting it on your lift, draining the oil, getting a new filter and oil from the parts guy, putting the car back outside and doing the paperwork.
 
I always change my oil after it has cooled enough so that I can remove the drain plug w/o burning my fingers and having oil spraying out sideways.

Thinner oil drains easier and and have read that more contaminents will be drained since they are suspeneded in the warm oil. Since I only drive my TR6 about 1000 miles
a year I only do 4 oil changes which comes out to be about every 4 months. I change it in the spring after the car has sat most of the winter, twice during the driving season, and at winter shutdown.
 
[ QUOTE ]
Clearly you guys have not ever made a living as a mechanic.

[/ QUOTE ]

You left out using the cheapest oil, too....

I'm inclined to think most mechanics might just take a little better care of their own cars than they do of those they're paid to rush through.
 
[ QUOTE ]
Clearly you guys have not ever made a living as a mechanic... about ten minutes to do the entire job...

[/ QUOTE ]

And clearly you are not retired. I can make that 10 minute oil change last all morning, especially if my wife has something in mind for me to do when I get done.
 
[quote I can make that 10 minute oil change last all morning, especially if my wife has something in mind for me to do when I get done.

[/ QUOTE ] /ubbthreads/images/graemlins/iagree.gif

Don't need to be retired for that... its good any time!
 
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