What oil to use? (and general servicing questions for 3.0rb)

[GTB Liberty]

. . . and here is another thread on "which is best" motor oil. The biggest disputed issue on motor forums.

http://www.bobistheoilguy.com for all the great "oil" debates.

Syn to Dino

If I put new, fully synthetic oil in my older engine, will the seals leak?

The short answer: generally speaking, not any more. The caveat is that your engine must be in good working order and not be leaking right now. If that's the case, most modern oils are fully compatible with the elastomeric materials that engine seals are made from, and you shouldn't have any issues with leaks. The longer answer:
Mixing Mineral and Synthetic oils - the old and busted concepts

For the longest time, I had this to say about mixing mineral and synthetic oils:

* If you've been driving around with mineral oil in your engine for years, don't switch to synthetic oil without preparation. Synthetic oils have been known to dislodge the baked-on deposits from mineral oils and leave them floating around your engine - not good. It's wise to use a flushing oil first.
* If you do decide to change, only go up the scale. If you've been running around on synthetic, don't change down to a mineral-based oil - your engine might not be able to cope with the degradation in lubrication. Consequently, if you've been using mineral oil, try a semi or a full synthetic oil. By degradation, I'm speaking of the wear tolerances that an engine develops based on the oil that it's using. Thicker mineral oils mean thicker layers of oil coating the moving parts (by microns though). Switching to a thinner synthetic oil can cause piston rings to leak and in some very rare cases, piston slap or crank vibration.
* Gaskets and seals! With the makeup of synthetic oils being different from mineral oils, mineral-oil-soaked gaskets and seals have been known to leak when exposed to synthetic oils. Perhaps not that common an occurrence, but worth bearing in mind nevertheless.

Mixing Mineral and Synthetic oils - the new hotness

That's the thing with progress - stuff becomes out-of-date. Fortunately for you, dear reader, the web is a great place to keep things up-to-date, so here's the current thinking on the subject of mixing mineral and synthetic oils. This information is based on the answer to a technical question posed on the Shell Oil website.
There is no scientific data to support the idea that mixing mineral and synthetic oils will damage your engine. When switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because synthetic oil and mineral-based motor oil are, for the most part, compatible with each other. (The exception is pure synthetics. Polyglycols don't mix with normal mineral oils.)
There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months.
There was a time, years ago, when switching between synthetic oils and mineral oils was not recommended if you had used one product or the other for a long period of time. People experienced problems with seals leaking and high oil consumption but changes in additive chemistry and seal material have taken care of those issues. And that's an important caveat. New seal technology is great, but if you're still driving around in a car from the 80's with its original seals, then this argument becomes a bit of a moot point - your seals are still going to be subject to the old leakage problems no matter what newfangled additives the oil companies are putting in their products.

http://www.carbibles.com/engineoil_bible.html

Mobil ONE fully synthetic (personal choice - I like the packaging )

[teK--]

I was considering going to Castrol Edge 5W-30, however now that the problem of dino vs synthetic appear to be well sorted the only question is if I will start having problems going to a thinner oil (currently running Magnatec 10W-40). Edge does not come in 10W-40 that I could see.

Castrol's website suggests either of the two above oils are suitable.

[smythie]

Oils with a 40W hot rating will be better for your car than those with a 30W hot rating if you intend getting it hot or running in hot temperatures (which can and does happen in Melbourne) - 40W is thicker when hot than 30W, it should provide better protection. The 5W cold rating will be better than the 10W cold rating in cold temperatures. It's up to you but for Australia I'd be thinking 10W-40W over 5W-30W. YMMV

[teK--]

Thanks Smythie all good points. 90% of the time I'm doing commuting in mixed highway/urban so the engine is seldom running very hot during these times.

I'm more concerned about track events in Summer. I would think that short runs of 1min or so with good warm down would be much less demanding on oil than continuous laps around Sandown.

Do you think that in the short runs scenario, that the higher resistance to degradation for synthetics, would outweigh the disadvantage of it being a thinner oil?

[georgehifi]

I would use both, Castrol Edge Sport 5w-30w for normal driving and for track days then I would change to Castrol Edge Sport 10w-40w, but you never get this on special, it's always around $50-$60.

Cheers George

[BUDDAH]

I would use both, Castrol Edge Sport 5w-30w for normal driving and for track days then I would change to Castrol Edge Sport 10w-40w, but you never get this on special, it's always around $50-$60.

Cheers George

Why would you do this ?

[teK--]

I would use both, Castrol Edge Sport 5w-30w for normal driving and for track days then I would change to Castrol Edge Sport 10w-40w, but you never get this on special, it's always around $50-$60.

Cheers George

Thanks George it appears there is no 10W-40 Edge Sport, only 0W-40; is this what you were thinking of? Perhaps using 0W-40 will give enhanced cold weather protection since when the engine is at normal temp it will be at the nominal 40W anyway? Or am I going to be burning oil until the engine's warm?

[smythie]

personally I'd be inclined to go the 10w-40. It is reportedly good to lower than -10 degrees during startup. That said, 5W-30 probably isn't going to hurt your engine either

[georgehifi]

I would use both, Castrol Edge Sport 5w-30w for normal driving and for track days then I would change to Castrol Edge Sport 10w-40w, but you never get this on special, it's always around $50-$60.

Cheers George

Thanks George it appears there is no 10W-40 Edge Sport, only 0W-40; is this what you were thinking of? Perhaps using 0W-40 will give enhanced cold weather protection since when the engine is at normal temp it will be at the nominal 40W anyway? Or am I going to be burning oil until the engine's warm?

For your track days in summer put in the 0W-40. Winter I would just use the 5w-30 it has kept my H6 going like a Swiss watch and is good for the economy as well.

Cheers George

[alfadaz]

I went a bit extreme on this and am running Penrite SIN 5 which is a 5W60 oil.
I changed to this after buying the car (no idea what was in it before) and seeing high oil use, doing one oil change using Penrite HPR5 (5W40), and seeing the same.
There is a general suggestion that AVLS and similar systems don't like a higher viscosity oil at all (possibly a gross generalisation, but not one I want to test the hard way).

So my thinking was that if I could keep the cold viscosity down but not have it thin out as much when hot I'd be right. Seems to be working but its an expensive way to avoid throwing the odd 500ml (it does still need it sometimes, - but not as often) of oil in.

Has anyone with oil consumption issues seen any difference in different oils? In reality there are too many variables (type of driving, weather) for me to be sure that teh difference in oil is significant, but some other experiences would be informative.

Not in a big hurry to take any risks - no matter what the oil costs it is cheaper than engine failure...