I did a search but couldn't find anything that answered my questions totally.

So I'm going to do my oil change soon and I have a few questions about the type of oil I should use. I'm not new to changing my own oil, I just want to see if there is anything out there that is better.

Okay, so my owners manual says I should be using 15-W40 for my weather conditions. I always seem to have a hard time finding this oil number. Would it be safe to use a different one? I'm looking at 15-W50. What is the difference, really?

Also, what are the benifits of using a synthetic oil? How about synthetic blends?

And is it safe to use "performance oil" on my car? I found this Mobil 1 15-W50 Performance Oil at the store and it seemed really good. I can't seem to find this oil on the Mobil 1 website. They have a 15-W50, but not the one I was looking at. I wonder if it was discontinued or something.

Anyway, thanks in advanced for the help.

Really, you searched and couldn't find THIS topic?

Mobil1 0w40, 5w40, or 15w50 are all fine choices for TX.

15W40 should be readily available. It's typically a viscosity for "heavy duty" engines such as diesels. These HDEOs are very robust--meaning they have a base stock that won't shear easily with mileage and they have plenty of additives for detergency and anti-wear. Look for Chevron Delo or Mobil Delvac 1300. Both are very good oils and likely to be carried by WalMart and other retailers.

The main advantages of synthetic oil include the ability to extend the oil change interval and the ability to tolerate higher temperatures.

You could probably, depending on how you drive and the condition of your engine, go the full duration of the BMW oil change lights with synthetic. With non-synthetics, you probably would should go only half that mileage.

If you look at a cylinder head from an engine that used synthetics most of its life, you'll see much cleaner parts vs. one run with regular oil. Not saying that the latter is bad, but you will notice more discoloration due to varnish, etc.

Cost-wise, it's up to you. Syns typically cost 3-5x regular oil, but only extend the miles between oil change 2x or so.

you certainly didn't search very hard..

http://forums.bimmerforums.com/forum/showthread.php?t=337588

you certainly didn't search very hard..

http://forums.bimmerforums.com/forum/showthread.php?t=337588

I found that, but had different questions. Thanks.

i would use 5-30 BMW synth if i were you.

thinner oil will allow the engine to produce more power by not fighting the heavier wieght of say 15-40.

its also recommened for the 3 series by bmw...
mobile 1 5-30 will do it too, its basically the same stuff.

i would use 5-30 BMW synth if i were you.

thinner oil will allow the engine to produce more power by not fighting the heavier wieght of say 15-40.

its also recommened for the 3 series by bmw...
mobile 1 5-30 will do it too, its basically the same stuff.

But these numbers varie by weather conditions don't they? How can BMW recommend one specific oil number for all 3-series driviers?

The answer is they used to vary the viscosity range based on ambient temperatures. And, it depends on how you run your car, as well. On my wife's 1997 328i, a 10W40 is recommended--this was before the days that BMW put in synthetic as factory fill. With synthetics, BMW is able to get away with a single multi-grade oil for most operating conditions--in this case, a 5W30.

I believe that our engines call for ACEA A3/B3 oils. This is a European spec for an oil that stays in grade over extended duration. Look for that on the various oils you're considering. Mobil 1 5W30 is a fine oil, but is too thin to pass A3/B3. Instead, it's rated A1 or A5. The oil that BMW dealers sells meet the A3 spec, as does Mobil 1 15W50, Castrol Syntec 10W40, 5W50, Redline (not sure what grades) and several others.

I personally think you'll be fine with 15W40 in Texas. It doesn't get too cold out there, right? My used oil analysis with Chevron Delo have come back looking really good on my e34 2.5L, even with 7K miles on it.

I gave up looking for 15W-40 oil a long time ago and switched to 10W-40, which is a little easier to find. I've had no problems.

What does the thickness of an oil matter actually? Why can't I put whichever number I want? This is the true question I'm asking here.

When engineers design an engine, they spec out materials, part clearances & tolerances. The clearance of the main bearings with the crank requires a certain viscosity (thickness) oil--too thick and you'll be wasting horsepower pumping the oil; too thin and you risk excessive bearing wear.

Engine design philosophies differ--new Japanese designs use 5W20 to minimize friction and improve fuel economy. The lighter weight oil is also needed for high rpms, such as in the Honda S2000. German engines until recently were designed to run on higher viscosity oils--probably due to a heritage with the Autobahn and extended, high speed operation. Also, German engine designs have been known for longevity and durability, particularly the bottom ends.

Does that answer your question? Just use what the manufacturer has recommended--although it's usually safer to go up with notch in viscosity rather than the other way around.

My car calls for 15-W40, which I said was hard for me to find in my area. So from reading this now, 15-W50 would do just fine?

Yep, 15W50 would work just fine if not better than 15W40 in your case.

Yep, 15W50 would work just fine if not better than 15W40 in your case.

Welp, I just did my oil change a few minutes ago. I'm happy to say I went with Mobil 1 Fully Synthetic 15-W50 (Extended Performance 15,000 miles guaranteed)

The car runs SMOOTH!

Thanks for everybody's help and input. :)

i would use 5-30 BMW synth if i were you.

thinner oil will allow the engine to produce more power by not fighting the heavier wieght of say 15-40.

its also recommened for the 3 series by bmw...
mobile 1 5-30 will do it too, its basically the same stuff.

Mobil1 5w30 is very thin for a 30, it's practically a 20. There's a reason it doesn't carry BMW approval. Mobil1 0w40 does.

Mobil1 5w30 is very thin for a 30, it's practically a 20. There's a reason it doesn't carry BMW approval. Mobil1 0w40 does.

what he said.

Mobil1 5w30 is very thin for a 30, it's practically a 20. There's a reason it doesn't carry BMW approval. Mobil1 0w40 does.


Where do you find out what oil(s) BMW approves ?

Where do you find out what oil(s) BMW approves ?
BMW will have it's approval cert on the back - such as BMW LL-98 etc.