QUOTE(Optiplex330 @ Apr 17 2012, 04:50 PM)
If your manual says to use 20W50 it means you can use xW50. 'x' could be 0 or 5 or 15 or 20, doesn't matter. But should it be 0/5/10 then make sure it's Fully Synthetic. But if you are using 20W50, then Mineral is perfectly fine.
With 10W40, your car might feel 'lighter' or 'more powerful' or slightly better fuel consumption but may be more noisy. For long term, I reckon it might be better to go back to 20w50. My 2 sen
For Proton BLM/FL/FLX, Proton appears 2b inconsistent in its recommended SAE grades...

For BLMs and pre-Oct(?) 2011 FLs, Proton User Manuals rec 20W50.
Then later in 2011, an amendment sheet was added to FL User Manual changing the SAE grade to 10W30!!
However, most Proton SCs appear 2b using 10W40 during official OCIs...

Now FLXs Manual also rec 10W30. BUT SCs still supplying 10W40?

What is Proton's TRULY OFFICIAL stand/rec on this aspect of maintenance?
Left to "whims & fancies" of SCs? Or mayb even in the hands of Users/Owners?

Anyone, pleez....
This post has been edited by zeone: Apr 22 2012, 05:25 PM