Depending on the age of the engine. The older the engine the lower the viscosity rating would be needed.

Get some Asda 20/50 this will be fine.

Sorry only joking Castrol GTX is a good oil for your car or even the semi synthetic GTX magnatec

SLX is a fully synthetic oil - recommended for later BMW multivalve engines with longer service intervals. Is very pricey and not really worth using in your 318is. Use a good brand semi synthetic oil.

Andy

I only use Mobil 1 5W 40 - the new blend stuff. I also used it before this new blend.

I pay about £20, its about £30-35 in Halfords and £24+vat trade.

I get several gallons from France as like the beer its cheaper. So when I do a beer run to France, I do an oil run too!!

Hi,

As I'm new to BMW's, which oil could someone recommend for a '99 323Ci. (40k mileage).

Thanks for your help

I would say, spend about £20 on 4-5 litres and you will get a decent oil.

I would get Mobil1 (fully synthetic) or Castrol Magnatec (semi-synthetic) is also good.

Basically if you pay about £5 a litre it is good stuff.

Don't get cheap 'Highway' motor oil at £2.50 per 4 litres.

Comma Triple R is also decent, about £15-20 for fully synthetic.

When choosing an oil you have to decide on what viscosity and what quality you want to use.

The viscosity is specified by the car manufacturer. e.g. for my 1990 E30, the manual says 15W-40 for ambient temperatures between -20°C and 30°C, which pretty much covers any conditions in the UK. 10W-40 is recommended for -30°C to 15°C, so on a warm day it might be a bit thin. Using a lower viscosity oil (than specified) is pretty pointless since it will just get used up faster and may not provide the required protection.

The quality of an oil is tested by the API and the ACEA. The API grades for petrol engines run from SF (crap) to SL (best). For diesels, the best grade is CF. Castrol GTX is SJ rated (pretty good). The ACEA grades go from A1 to A3 for petrol engines and B1 to B4 for diesels. Good oils also have recommendations from manufacturers. So a totally kick-arse oil would be API SL, ACEA A3/B4, recommended by VW and BMW, for example.

Whether it's mineral or synthetic is not really important in itself - a good semi-synthetic is better than a poor fully synthetic oil. Personally, I wouldn't run an older engine like mine on synthetic, because it's not available in a high enough viscosity.

Also, the brand is not really important either - the quality certifications are what you should go by.

I remember reading an article about synthetic oil some years back. It stated that the change to synthetic is best done early in the engine's life (but after it'[s fully run in). People that changed over on higher mileage motors had no end of problems with oil leaks. These didn't seem to be resolved even after changing back to a full mineral base oil or a semi synthetic again.

I ran my Maserati Biturbo on Valvoline Synpower from when I had it at 35K miles, (3 years old) up until recently when I took it off the road, with no leakage problems.  I guess I was lucky.

I use Magnatec in the 540, but change it more regularly than the service indicators would dictate.

Andy  540i  Birmingham

For even more information, you could check out this website I've just remembered:

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

"I wonder who actually makes this Halfords stuff. I think it's what I'll be using from now on anyway."

Whoever makes it, I say  it'll be less money for the Hakkinen's and Coulthards of this world!