Oil change

[fabulicious]

Will be doing an oil change soon and am looking for some recommendations on which grade/type to go for.
I am not fussy on cold start protection as the car is not used daily therefore was going to go for something that offer's more protection against heat.
Any wise and wonderful suggestions?

[Coops]

10w-40 semi synth seems to be a popular one

think I used 15w-40 semi on the Williams when I had it

[fabulicious]

15w changes less with temperature than a lower index correct?

[Coops]

no, 15w changes more as its thicker at a lower temp than the 10W, they have equal viscosity at 100 degrees (that's the 40 part)

the W represents a scaling factor as well, which is why although the oil is at a higher viscosity when cold than when warm, the number for the operating temp is higher than the W number given.

if that makes any sense!lol!

[fabulicious]

:beamme:

I havent a fookin clue what your on about coops! :lol:

So what do i go for. A 5w40 then? 5W30 perhaps?

[Coops]

10w 40 semi will be fine unless you have a worry about tappet noise etc

any thinner and you'll be back on here worried about low oil pressure on cold start ;-) lol!

[Yanoo_]

If I were you, I'd use 10w40 (semi-synth) or even more 5w50 full synth oil in my car for daily use (in the UK). In Hungary, where the summer is much hotter, I'm using Mobil 1 5w50 full synth, very good oil.

[Yanoo_]

If I were you, I'd use 10w40 (semi-synth) or even more 5w50 full synth oil in my car for daily use (in the UK). In Hungary, where the summer is much hotter, I'm using Mobil 1 5w50 full synth, very good oil.

Damn edit button, so try it again:

If I were you, I'd use 10w40 (semi-synth) or even more 5w40 full synth

[fabulicious]

Ok thats perfect chaps..wanted a balance between UK and Continent views.
Yanoo I'd say you notice the effect of ambient temps in Hungary a lot more than we do here in the british isles as I did also in Italy.

So 5W40 full synth for high heat ambient locations and 10w40 for all others.
The 5w40 behave well on the motorway? Your not running any coolers are you on the 1?

[Yanoo_]

No, perhaps I was ambigious:

For Renault F7 engine series:
10w40 or 5w40 for colder climate & daily use, or track with oil cooler (Mocal or other proper oil cooler)
5w50 or 10w50 for hotter climate & daily use, or track with oil cooler, or for colder climate & track use without oil cooler
10w60 for hotter climate & track use without oil cooler

The smaller the number before W, the less viscous the oil in the cold.
The higher the number after W, the more viscous the oil at high temperature.

[Yanoo_]

There is only the OEM heat exchanger is in my car. But I use 82C deg temp thermostat, this setup with Mobil 1 5w50 is good for cruising and hill climb, the oil temp remains below 110 C deg at all time, if the ambient temp is above 25 C deg. But under 25 C, the engine cannot get warm up properly.

[fabulicious]

OK so provided I have good oil pressure, no aftermarket oil cooler or thermo,
with 10w50 fully synth I should be able to run comfortably in high ambient temp locations, take a few laps around a track and at the same time be comfortable with cold starts. 8)

[Yanoo_]

OK so provided I have good oil pressure, no aftermarket oil cooler or thermo, with 10w50 fully synth I should be able to run comfortably in high ambient temp locations, take a few laps around a track and at the same time be comfortable with cold starts. 8)

Yes, but 5w50 would be better in winter.

4 oils' kinematic and HTHS viscosity are compared directly in this chart, you can see the difference between different grade oils (higher the number of viscosity, the more viscous the oil):

http://www.dp-automotive.hu/egyeb/4oilskinvisc.jpg

[fabulicious]

Yanoo can you explain the "high shear dynamic viscosity chart" in laymans terms.
i think from the rest of them it shows that at a certain temp all the oils are going to do the same thing. no?
Then I heard some oil's can even get thicker as they warm up.Is this true?

[Yanoo_]

HTHS viscosity is a very important oil property, it has important implications for such factors as engine fuel economy, valvetrain wear and bearing protection. Higher the HTHS viscosity, the better the engine protection. However too high HTHS viscosity can restrict the engine's ability for revving up easily, especially if the higher HTHS is combined with higher oil grade (w50, w60). Therefore in a competition engine too high HTHS value is not favourable. Ester based (racing) engine oils (like Motul 300V series) have outstanding HTHS viscosity, while their kinematic viscosity may be low. For example the HTHS viscosity of Motul 300V Power 5w-40 (full synthetic, ester based racing oil) is 4.51 mPa*s, it exceeds the HTHS value of a quality 5w-50 full synth (not ester based, but PAO based) engine oil, and it's very close to a less quality 10w-60 grade oil's HTHS value. A minimum HTHS viscosity for a given oil grade is determined by the SAE J300 regulation. Unfortunately HTHS viscosity is not so frequently represented in the oils data sheet, therefore my software uses the allowable lowest HTHS value for the given oil grade, if it's unkown.

[Yanoo_]

Then I heard some oil's can even get thicker as they warm up.Is this true?

No it's not true, but viscosity improvers (oil additive) try get the oil thicker. The compounds of VI improvers are sphere shaped in cold, they can roll on one another easily. When the oil warms up, these spheres open, and they become rod shaped. These rods can restrict the movement of other compunds / molecules, thus the kinematic viscosity of the oil won't be so low as it would be without VI improvers.