If I am unsure on what oil has been prevously used. What

mix/type of oil would be best.

 

I have just bought some Castrol RS 0/40 and am worried that if I use fully synthetic it may dislodge some crap... Is this right?.

 

I have runa search but there seems to be a lot of conflilcting advice.

 

 

 

Cheers.

I've used rs 0-40 last 25k miles. Until I had the car it always had Shell semi synth for the first 110kmiles. Last owner also had a garage do a flush on it thinking it would help cut hydraulic tappet rattle on startup.

 

No leaks not burning and only tappet rattle if I dont use the car for weeks and the oil drains back.

http://www.chris-longhurst.com/carbibles/engineoil_bible.html

 

Quote

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. I learned this lesson the hard way! 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 sythetic 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 occurance, but worth bearing in mind nevertheless.

Unquote.

Cheers lads.