Re: To Jim Cash (archive)

Hi Jim, I've been using sythetics for a long time and recently I've changed the oil to Mobile 1 15w 40 because I was told BMW dealersdoesn't use fully synthetic oil for pre 99 540ia.?? they use some kind of semi-sythetics. Also, should I use 15ws for more protection or BMW recommended 5ws? And in your opinion, what's the best sythetic oil in the market that's easily obtainable from local shops? I am thinking to change to MOTUL because I heard they are very good?
thank you again:)

I have no idea what the best synthetic oil is - you could spend a career trying them all and still never know unless you did a lab test on each.

I have had good luck with Castrol over the years (old oil) and when I switched to synthetic )at 20k kms on the E39 I tried Mobil 1 15w50.

That was much too thick and I noticed a difference in performance and milage. Then BMW started selling their own branded synthetic (Valvoline at that time) in the 5W40 flavour.

That was a great oil. Better performance and milage, and stayed clean because it is synthetic and no cooking.

Now they have gone to Castrol - which is great, but it is only in 5w30 (which I "think" might be a tad light in hot weather - but they are betting the warranty on it so ???)

My next step is to see if they will go to a 5w40 - which I would prefer for the hot weather, abd use the 5w30 in the winter.

But whatever you choose get away from that 15 grade. To sluggish for lubrication on startups and you will not get as good over all lubrication in cooler weather.

At least that is my approach.

Cheers
Jim Cash

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