What oil....?

[Jake Casson]

Thanks SRR2.

Yes it is synthetic. Did you know BMW states 5W-30 for the E39 535 but 10W-40 for the E34.

Looks like i'll be putting the 5W-30 in then.....

[araine901]

Are you saying that in the summer here in Phoenix when it does not get below 100 F (even at night) and is over 110 most days that 10-30 or 0-40 is just as good as 15-50? Just currious.

[SRR2]

Well what's the operating temperature of your engine when it's 80F? Say 220F. And what is it when it's 115F outside? Oh, 220F. Of course, you're going to be pulling a lot more air through the radiator at 115F, but the engine oil doesn't know anything about it.

BTW, if you have an E39 with the 7.2 or higher Motronic, the electric thermostat actually *lowers* the engine operating temperature in high ambients like yours.

Look at BMW's current oil recommendations. 5W-30 quality synthetic for most models (dunno about M-cars) for ALL TEMPERATURES!!

[SRR2]

But the recommendation for the E34 was mineral oil, at least for the first few years of production. I don't know if the owner's manual changed the recommendation to synthetic oil toward the end of the E34's run. I kind of doubt it.

I suggest you guys browse on over to bobistheoilguy.com (I'm not joking) and spend some time reading their forums and archives. You will learn more about oil than you ever thought possible.

[Zeuk in Oz]

For a E34 535is would you say is best, 10w-40?

If you're bored and want some entertainment, do a search on this forum under "oil".
Will keep you occupied for a month.
I use Mobil 1 0W-40 in my E 34 but Shell Helix Ultra 5W-40 in my ML 270 CDI (diesel) because that is what the dealer uses - I do an oil change half way through the recommended period - approx 11,000 km . I have started using Mobil Delvac 1 5W-40 in my diesel F250. (Special order through my local auto shop - no one stocks full synthetic diesel oil in Oz, as far as I can establish.)
Interesting that all of these have an upper figure of 40 despite living in a temperate climate.

[JonE]

M1 0-40 here in typically very cold winter conditions. Easier initial start-up with the synthetic in frigid weather. The car seemed to run better overall with it. I also like the fact that I can go several thousand miles more between oil changes.

[araine901]

Well what's the operating temperature of your engine when it's 80F? Say 220F. And what is it when it's 115F outside? Oh, 220F. Of course, you're going to be pulling a lot more air through the radiator at 115F, but the engine oil doesn't know anything about it.

BTW, if you have an E39 with the 7.2 or higher Motronic, the electric thermostat actually *lowers* the engine operating temperature in high ambients like yours.

Look at BMW's current oil recommendations. 5W-30 quality synthetic for most models (dunno about M-cars) for ALL TEMPERATURES!!

Point taken. I am used to feeding my (air cooled) 911 15-50 M1 so I was feeding the 540 the same thing during the summer. Probibly overkill, but I feel guilty when its 117 out and I am running the A/C full blast and sitting in traffic.