Oil Type You Guys Use?

[rick]

and if anyone is interested, there is some excellent tech stuff here on these two pages http://www.bobistheoilguy.com/forums/ubbth...d=53&page=1, as well as the rest of that board, if you can sort the wheat from the chaff.

[JimAttrill]

All that off the top of your head! I reckon that post should go into the Tech Archive. Now I know why Shell's 'synthetic' oil is much cheaper than Redline.

ps. If you really want to do some nice and easy symbols like 100°, ™ and currencies like € ¥ etc, you can download a tiny free program called Allchars, handy if you need é, â, and even ¿ and runic stuff if you are into heavy metal B)

http://allchars.zwolnet.com/

[FridgeFreezer]

I've just skim-read this but it's worth remembering that there are several generations of RV8, a key change was when they went serpentine and changed from the old-style oil pump, as described by Nige, to the more modern one, I believe LR's oil specs for the more modern (4.0 & 4.6) lumps reflects this. Most people here don't have that setup (and being a luddite my 4.6 runs the old front end ) so sticking runny oil in will be a bad idea. I made this mistake once with my 3.9, the pump un-primed itself on a climb

Since then I've run either Comma 20W50 or Castrol 15W40 and everything's fine.

I'll hand back to the adults now.

[rick]

A few more things that I forgot to add.

Viscosity Index Improvers.

These are clever little molecules (polymeric thickeners) that when added to an oil help it resist thinning under increasing temperature. These are basically a form of plastic that is added in a powdered form at high temperature (IIRC over 200*F) and take several days to become solvent.

Only the big blenders use this form, (Mobil, Texaco, etc) the small boutique blenders buy it already in solution for easy blending.

VII's are needed to make our mineral oil based multi-grade oils, otherwise everyone would still be using straight grade oils.

Say our blender wants to make an SAE 10W-40, he can select a lighter base weight oil that corresponds to a 10W on the cranking pressure scale, add some VII of the correct type and voila, he has a multi-grade !

The downside with VII's is that;

1. they take up space in the oil that could be used for something else, eg. good old oil or another important additive.

2. They tend to shear under pressure and load. What this means is that your original 12.5 cSt @ 100*C 10W-40 can soon become a 10 cSt @ 100*C 10W-30 without much effort. Today's VII's are a hell of a lot more stable than yesteryears, but they still do this.

VII's in gear oils are even worse off as the environment in terms of shear is much harsher.

The only VII's that I'm aware of that don't shear are the ones that Castrol use in some of their premium synthetic products formulated in Germany. The technology was absolutely cutting edge only a couple of years ago, and I remember the amazement of some of the Yanks when they reverse engineered a 0W-30 with gas spectography. Having said that, I'm sure the other big blenders have some tricks up there sleeves as a number of premium oils from all the big boys have a wide viscosity spread and are extremely shear stable.

Synthetic oils and VII's.

Mostly, they are in much smaller quantities or not at all. AFAIK, most of Redline, Motul and number of Mobil's products don't use any as the synthetic bases are so stable across such a wide temperature band. Others, such as the above mentioned Castrol ones use small amounts and are really base oils anyway, and others used in oils like Mobil 1 0W-40 do use VII's and shear back to 0W-30 under use, but VII's need to be used in these wide viscosity oils to get the required viscosity spread. This could be where M1 0W-40 gets a bit of bad reputation when used in older, higher clearance engines.

Simply put, if you want an oil that doesn't shear in use, use one with as narrow viscosity spread as possible, however some of the wide spread oils (Mobil Delvac 1 5W-40 being a case in point) are some off the most stable oils on the market, showing no viscosity variations over distances exceeding 100,000km on one oil change.

Volatility.

All oils are volatile, regardless of base type. This means that they will tend to evaporate under heat and load. The volatility is expressed as a NOACK % on the spec sheets. Obviously lower is better, with the best ones hovering in the region 6-8%. Mineral based lubes are often in the low to mid teens, even the good ones.

[Guest otchie1]

Group V

They are also bloody expensive. They can be derived from many different sources, and are usually a naturally occurring fat that is esterised. (acid/alcohol/heat) Crop oils, animal fats, etc are used to create these oils.

ahhh, we're back to the days of whale oil, cool, I'll get me harpoon :-)

[welling4x4]

Ahh, you have trouble differentiating engineering specifications from sales blurb, my bad.

Wanna buy some STP?

would having to thick an oil make my engine run rough on idel as I have been told that this is causing my flat spot on tick over ??????????? any ideas pep's.