pre-heating engine oil

[dannylt]

So why would pre-heating the oil before starting up and driving off immediately be bad? The oil will reach proper temperature quicker, as will the engine, so what's wrong with that?

[Gridgway]

I don't think it is bad. But there are a few facets to the practicalities of it. Ie how do you pre-heat the oil?

 

If you can pre-heat the oil it doesn't feel that good to then send it round a cold engine especially en exotic one. Also if the engine is cold, how much good does pre-heating the oil do?

 

We have been here this season in the Radicals to reduce the number of hours spent running the engine at tickover to warm it up. It takes ages as the Radical has a very efficient cooling system with no temperature control on the oil (ie a great big oil cooler but no thermostat).

 

So we have a kenlowe coolant pre-heater and a heater pad on the DS tank. It does a reasonably good job of reducing the running hours.

 

Trouble is that you rapidly run out of amps at a race circuit, especially with 4 cars under one awning!

[Phil]

Would you all agree that a mono grade 60 would offer to much Resistance to flow at a cold temperature hindering start up?

 

Would you agree that a mono grade 10 would not offer good oil pressure, film strength at full running temperature?

 

So how does a MULTI grade work then, the oil is like a ball of string tightly wound chemical encased when cold, as it heats up there is a chemical reaction releasing the string and it stretches out to a given maximum ie a 30, 40 etch

So yes the oil does thicken up as it gets hot.

 

I would be worried about running a 60 grade in an engine designed around a 30 unless you are just racing it.

 

keybaud you are correct.

 

[Roger Ford]

So yes the oil does thicken up as it gets hot.

 

Only if you define "thicker" as "not as thin as it would otherwise be at this temperature" which is a fairly perverse definition.

[Gridgway]

Sorry have to reject that question. If you are going to talk techie about multi-grade oil, that's fine and good. Don't then ruin it by talking about "thicker"

 

 

[Gridgway]

oops, crossed with Roger!

[Phil]

Sorry

I am bad 😳

 

I was keeping it simple and yes I hate the words thicker and thinner, viscosity is the way forward.

 

So if you have an understanding of the grades and what they offer, my question is this, as the engine in question was designed around a 5w30 oil why use a 10w60 oil which offers far greater resistance to flow at high tempreture compared to the 30 taking away bhp and fuel econamy?

[Barry]

Quoting Gridgway: 

Trouble is that you rapidly run out of amps at a race circuit, especially with 4 cars under one awning!

 

Would one of these help?

[Dr Slotter]

Right, I'm going to have another go... All that multi-grade ratings mean is that a particular multigrade oil, say 10w40:

 

- has the viscosity of a mono-grade oil with a rating of 10w at cold temperatures

- has the viscosity of a mono-grade oil with a rating of 40 at high temperatures

 

The 'w' ratings are not directly comparable with the non-'w' ratings as the tests are different. The 'w' tests are done using a standardised 'Cold Cranking Simulator' which measures the maximum viscosity an oil will have at a particular low temperature (it varies with grade). The non-'w' tests are done using a viscometer which essentially measures the minimum amount of oil can flow through an orifice of a particular size in a particular time at a particular temperature (100 degrees).

 

Here is the viscosity (in centistokes) of 10w40 at different temperatures:

 

0 = 874

10 = 440

40 = 91

100 = 14

 

i.e. viscosity decreases with increasing temperature.

 

And for a 15w40 it would look like this:

 

0 = 1260

10 = 595

40 = 107

100 = 14

 

i.e. viscosity decreases with increasing temperature, but at a much greater rate, because it starts off with a higer viscosity (i.e. is more viscous at 0 degrees than 10w40) but is the same viscosity at 100 degrees.

 

All oil gets less viscous as temperature increases.

 

To answer Phil's question, you would change from 5w30 to 10w60 if you thought that the wear in the wear in the engine was such that you need the extra viscosity to support the formation of a thick enough oil film to protect the surfaces which were further apart due to the wear. You would have greater frictional losses but be controlling the wear.

 

Edited by - Dr Slotter on 21 May 2012 12:05:46

[Phil]

Interesting

 

So F1 for example use a 20 grade oil [ yes pre heated ] with there engines being very high performance, high revs, why do they not use a higher viscous oil like a 60?

 

[Dr Slotter]

That's because the tolerances in F1 engines are typically much smaller (order of magnitude microns/thou), dimensionally and/or surface finish, so you need can form an appropriately thick oil film with a less viscous oil. They also care less about wear.

 

Edited by - Dr Slotter on 21 May 2012 19:30:34