Doing things because that's how you were taught

[donkmeister]

I was changing the oil on one of my cars over the weekend. I was about to turn the engine on to warm it up first, when I stopped and thought "why am I doing this?". Well, I was taught that you get the oil warm before you drain it.

In winter, I suppose warm oil runs out more quickly than cold oil. Especially so with old types of oil. But I'm sure I was taught "running the engine will help push the oil everywhere and clean out the dirt". Well, what will it pick up that it didn't get on the previous run? Isn't the oil in the sump now just as dirty as it would be if I run the engine for another 10 minutes?

I drained the oil, room temperature, just the dirt that was already in it. Only difference was the removal of burn risks, and that there might have been a few teaspoons more oil drained out because it wasn't splashed around inside the engine first.

So, is there another reason I should have run the engine first?

Have you got any spannering habits that make no sense in the modern world?

[ian332isport]

Historically, it was to make the relatively thick oil a bit thinner, so you get more out. These days, modern oil isn’t much thicker than water, so not such an issue.

[Belle427]

Certainly helps in winter but I prefer to drain when its been sat overnight, does it get any more oil out that normal, probably not but makes me feel better.

[Crudeoink]

ian332isport said:

Historically, it was to make the relatively thick oil a bit thinner, so you get more out. These days, modern oil isn t much thicker than water, so not such an issue.

I'd agree with this. Hotter oil just flows a bit better so there's less of a film on the bottom of the sump when you drain it. I usually don't get the oil boiling hot, just warmed (unless doing my air-cooled car which requires the oil to be piping hot and holds about 12L of oil!). I've never thought about the 'dirt' at least with regards to oil temperature when doing an oil change.

[98elise]

donkmeister said:

I was changing the oil on one of my cars over the weekend. I was about to turn the engine on to warm it up first, when I stopped and thought "why am I doing this?". Well, I was taught that you get the oil warm before you drain it.

In winter, I suppose warm oil runs out more quickly than cold oil. Especially so with old types of oil. But I'm sure I was taught "running the engine will help push the oil everywhere and clean out the dirt". Well, what will it pick up that it didn't get on the previous run? Isn't the oil in the sump now just as dirty as it would be if I run the engine for another 10 minutes?

I drained the oil, room temperature, just the dirt that was already in it. Only difference was the removal of burn risks, and that there might have been a few teaspoons more oil drained out because it wasn't splashed around inside the engine first.

So, is there another reason I should have run the engine first?

Have you got any spannering habits that make no sense in the modern world?

Running the engine wouldn't make any difference to the contaminants. They don't hide elsewhere when the engine is cold.

As others have said it made a difference to the viscosity in older cars, but these days there's very little difference IMO. Engines and engine oils have moved on quite a bit.

[vikingaero]

When replacing a wheel, I still clean the hub surface and give it a thin coating of copperslip (or equivalent), because that's what I was taught.

Some people on PH will go apoplectic, say that I must be dead, and talk about shear forces etc.

My trusted mechanic does this too.

[E-bmw]

The shear forces are not relevant here, provided the clamping force is correct for the wheel/hub to rotate in relation to each other the bolt/stud would have to stretch, which it won't.

[donkmeister]

I certainly clean the mating surfaces. I hadn't considered just how corroded they can be until I saw someone demonstrating a quick buff up with a roloc disc.

I've got two drill attached things for this now; one has a central hole with wire brushes so you can do round the studs, the other is a flat face disc so you can do the flat parts of the mating surfaces.

Obviously you don't want to go mad and end up with wobbly faces, but just enough to scrape the crud off. I always douse it with water to keep the dust down, then a final wash with brake cleaner.

Re copper slip, a chap I worked with simply used to remove every wheel a couple of times a year for a clean, and he never had one seized on. Not suggesting we all do that but can't argue with results

[Pumalhd]

Our car was about 16 months old when we got it, and the alloy wheels were stuck fast to the hubs. It has never happened since as I always use a thin smear of polybutylcuprysil (PBC).

[ARH]

Always warm the oil before changing it. The last thing you want is cold oil running down your arm when underneath taking the filter off. Probably makes no real difference these days but I did my first oil change in 1974, and it made a difference then.

I always clean and coat the hub when taking a wheel off, or replacing a disc.

[Hustle_]

Pumalhd said:

polybutylcuprysilticexpialidocious