oil change ?

[BRETTCOLLINS]

Thanks for the info Dippy. Car is always warm in the garage. this is why I only run millers 10w60 all year round.

[Dippy]

Brett, I'm probably overcautious, but that's because I have K03s.

[andy123]

10w 60 is like gearbox oil though isnt it??if you want some advice from someone that really knows what their talking about, contact opie oils. They would probably be able to do you a very good price on whatever you require, deliverys within 48 hrs and i cant reccomend them enough.

[andy123]

10w 60 is like gearbox oil though isnt it??if you want some advice from someone that really knows what their talking about, contact opie oils. They would probably be able to do you a very good price on whatever you require, deliverys within 48 hrs and i cant reccomend them enough.

[andy123]

http://www.opieoils.co.uk/

dont be put off by them being in cornwall

[ChrisG]

Oil and filters are cheap - compared to the possible alternatives. I'm also using the VAG TDi filters, twice the size and hold about .75 of a litre of oil and that's only in a 1.8T !
Mobil1 0w40

[tartan_rob]

The S4/RS4 oil filter location is poo and has limited space. The S4 filter is bigger than the RS4 and even then it is only about 12cm long.

[oilman]

Hmm, that's me. It's my company Opie Oils.

10w-60, not good. The 10w is fine for cold uk climate (0w and 5w are better) it's the sae 60 that's out of grade, the tolerances on these cars are tight, really tight.

Explaining this is diffucult so there may be questions but I'll try my best to explain it in plain English!

Lets look at what oil specs actually mean and particularly the higher number which is in fact the oils SAE number (the "w" number is in fact the cold crank viscosity and measured in a different way) The SAE number is measured by the oils viscosity at 100degC.

Your cars require according to the manufacturers specs, sae 30, 40 and in some cases sae 50.

To attain the relevent sae number the oil has to be at 100degC (no thinner than)

SAE 30 11cst approx
SAE 40 14cst approx
SAE 50 18cst approx

Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid.

As viscosity varies with temperature, the value is meaningless unless accompanied by the temperature at which it is measured. In the case of oils, viscosity is generally reported in centistokes (cst) and usually measured at 40degC and 100degC.

SAE 60 is in fact 24cst viscosity at 100degC!

This is 33% thicker than an sae 50, 70% thicker than an sae 40 and over 100% thicker than an sae 30!

So, what's the problem with this thickness?

Well, this is measured at 100degC and at lower temps (70-90degC) all oils are thicker than at 100degC so the problem is compounded to some extent.

The downsides of such a thick oil (when not specified) are as follows:

Additional friction, heat and wear.
A reduction of BHP at the wheels
Lower fuel consumption

The thicker the oil is the more friction and drag and the more power the engine needs to move it around the engine which inevitably translates to less at the wheels.

So, when do we spec a thicker oil?

We do recommend the use of a 10w-50 or a 15w-50 but only in these circumstances.

1. If the car is heavily modded and heat/oil temperatures are excessive.
2. If the car is used on track and heat/oil temperatures are excessive.
3. If it's required by the handbook.

Our criteria for this is based on oil temps as an sae 40 semi-synthetic can handle around 110degC for limited periods whereas a proper synthetic sae 40 can hande 120-130degC for prolonged periods due to its thermal stability.

Once you see more than say 120degC for prolonged periods an sae 50 is adviseable as it is 18cst at 100degC and still 11cst at 130degC! This is in fact the same as an sae 30 at 100degC.

More importantly at 90degC an sae 40 is 15cst, an sae 50 is 20cst and an sae 60 is 30cst!

In a worst case scenario with thick oils (when not required) is that you will experience air entrainment and cavitation inside the bearings at high RPM.

I know this is technical stuff but oil is a combination of science and engineering and few people know enough about it to make an informed choice. Just because you have had no problems is not a good enough reason to use it, your engine would prefer and benefit from the correct oil.

Cheers
Simon

[JonnyX]

Oilman/Simon,

Thanks a lot for taking the time to post that. Very informative.

Jon

[oilman]

I suppose I should have introduced myself in the newbies section first but figured that some would know me anyway.

If I can answer any oil related questions please feel free to ask and I'll do my best to help.

Cheers
Simon

[BRETTCOLLINS]

My car is running this Oil because it don't have an oil cooler on it. See between 100degC & 110degC on the car alot of the time.

Will Re-think the oil, when the oil cooler is fitted.

But thank you for the information, very helpful.

[oilman]

An sae 40 (proper synthetic one) can cope with 120degC oil temps. An sae 50 140degC.

Cheers
Simon

[tartan_rob]

so it would be fair to say that a car with euK climate running oil at 80deg C (with cooler for example), could safely run 5w/40 in winter and 10w40/50 in summer?

[oilman]

0w-40 or 5w-40 all year round, no need to change summer/winter, that's what multigrades are for.

Cheers
Simon

[searider]

Out of interest, what typical oil temperatures do people see? Normal driving town / motorway etc.

My VR6 shows about 100C on gentle driving, up to 105 / 110C at 70mph (ish) 115/118C if "pushing on" 95mph and I have seen it at 125C on a very fast run - 120mph where possible middle of the night trip (on the Autobahn of course).
The VR6 has an oil/water oil cooler.

One thing I have noticed is that temperatures do seem to be about 5C cooler immediately after an oil change.

As far as I know the oil has been changed every 10000 miles and is 10/40 semi synthetic. car has 150000 miles total and is running fine.

Oilman - does this look correct for my car?

The only advice I can glean from the VW handbook is that it recommends you slow down if the oil temperature exceeds 140C!