Hi all, I have a BMW 320D ED E90 2010 with 138K on the clock. For its upcoming annual service, I was purchasing the oil filters etc. and was advised by a reasonably experienced mechanical that I should try 10W 30 oil instead of BMW recommended 5w 30 (ive used Castrol magnatec for the last 2 services). He said that use of 10w30 will also improve the engine noise (it is noisy actually).

Any genuine advice on this would be much appreciated.

The only difference between the two oils is the viscosity or as the Americans call it the 'weight' which is related to the oil flow at certain temperatures. 

Your engine should be fine with each although for older engines I would be tempted to go for the 10w30.

However, there is a huge difference in oil quality so buy the best you can for your money.

18 minutes ago, Trevor said:

The only difference between the two oils is the viscosity or as the Americans call it the 'weight' which is related to the oil flow at certain temperatures. 

Your engine should be fine with each although for older engines I would be tempted to go for the 10w30.

However, there is a huge difference in oil quality so buy the best you can for your money.

Many thanks Trevor, I used previously Castrol magnatec which I thought was a good quality. Is that a good brand for 10w 30, if not, what recommendations? Also, what quantity of oil is required for my model.

Castrol Magnatec is a great oil but there are others that compare such as Mobil 1 and I recently tried Petronas in my Z3 and it is absolutely fine....no Vanos noise or valve rattle, and a lot cheaper as well.  

Halfords do great deals periodically on the above makes

14 minutes ago, Trevor said:

Castrol Magnatec is a great oil but there are others that compare such as Mobil 1 and I recently tried Petronas in my Z3 and it is absolutely fine....no Vanos noise or valve rattle, and a lot cheaper as well.  

Halfords do great deals periodically on the above makes

And how much is needed?

Try this link

https://applications.castrol.com/oilselector/en_gb/c/search?_ga=2.30320191.1280854334.1508926439-1291265006.1508926439

4 minutes ago, Trevor said:

Try this link

https://applications.castrol.com/oilselector/en_gb/c/search?_ga=2.30320191.1280854334.1508926439-1291265006.1508926439

One more think please, while searching for I noticed there aren't many 10w30, the lowest I see is 10w40 and then upwards. Also unable to see petronas on Halfords or eurocarparts.

Here's a link for Halfords...

http://www.halfords.com/motoring/engine-oils-fluids/engine-oil?brand=Petronas&pageNo=1&pageSize=21&sort=we_recommend