SAE 20W-50? Correct oil grade?

For a 1989 BMW 325i (E30) – southern United States climate?


Why take well-intentioned, but possibly incorrect, advice that may be offered regarding the correct viscosity for your situation?

Instead, open the glove compartment, take out the Owner’s Manual, and read the relevant section. The people who designed and built your engine are the authorities, and the information in the Owner’s Manual is what you should be using.

If for some reason you do not have an Owner’s Manual for your car, you should obtain one, as there are many issues in addition to oil viscosity that the manual can inform you about.

Agree with VC; the owner’s manual (world’s Least Read Best Seller) should be followed. In tropical countries where I’ve worked, 20W50 is the oil weight normally uses.

You may live in S. Califronia, but if you go to the mountains to ski in February, and start the car on a cold morning, you will damage your engine, so a lighter multi-grade would normally be recommended by your owner’s manual. PLEASE READ IT!!!

When BMW first started selling cars all over the US they specified the 20W50 grade, since German drivers need it at 100 mph on the autobahns. Minnesota and other northern states drivers burned out a lot of engines with cold starts before BMW discovered the real conditions of the US driving environment.

Thanks for the advice. I do have an owner’s manual, and I did check it. The oil weights listed for temperatures from 20F up to 120F are 15W50 and 20W50. In my area (south Louisiana, we rarely dip below 30F and at times reach 100F (like today). (The 20W50 range is closer to my climate.) This car is used only occasionally for weekend driving. The reason I asked the question is that our local oil change store suggested that I should use 10W40 (as I do in my other car) since I drive the car only on occasion. I did not know if that was a professional call or just an opinion. Thought I would check here. Thanks

For me with BMW’s like this it depends on if you’re using regular or synthetic oil. Synthetic I’d give the nod to a 40 weight, with non-synthetic a 50 weight. A 50 weight non-synthetic is going to thin down significantly anyway with use.

You already have your answer from the manual. On the off chance that BMW changed its mind after printing the manual, you might ask a nearby BMW dealer’s service department.

20W50 should be perfect for that car in southern Cal.

I have an old BMW and an old Volvo of similar vintage, both with over a quarter-million miles on them, both have always used Castrol 20W50 (even when I went to Iowa for Christmas!) I recently got a couple of bottles of Castrol that were pretty odd-looking. I sent in samples, and they reported back that the oil was “within blending tolerances”. They must have mighty liberal tolerances. After 30 years using the same oil, next oil change will be a different brand.

Damn, I hate to hear that. I’m ready to change my oil, and have been using Castrol 20W-50 for decades in my Toyotas, both over 200,000 miles. If they changed the formula, what is a good alternative?

That sounds like the start of a very LONG Car Talk thread!

You’re saying the formula has been changed. But is it better or worse then their previous formula???

I would never use 20/50 in a cold climate or if the car is used for short hop driving. In hot climates, and especially with longer trips (say 20 miles, etc.) I don’t see a problem with 20/50 at all.
On my old Mercury I used strictly 20/50 in it from about the 175k miles mark until I sold the car at the 420k miles mark with never a problem.

The US has one of the most varied climates of any country on earth. Europeans often can’t grasp that. In the tropics I happily used 20W50, since the coldest temperature was 25C or 77F.

For short hop driving you want to minimize cold start wear. 20W50 would not be a good oil. But you can buy 5W50 synthetic which is good for those cold starts and high speed highway driving.

If I lived in the US South, and had the driving pattern of OP, I would use a synthetic 5W50, or a 10W40 non-synthetic, if price was a problem. Most good oils will state if they meet BMW specs. In the mountain region, a 5W30 or 5W40 synthetic is suitable for most cars. BMWs in North America are not as stressed as they are in Germany where they have to be able to cruise at 100mph for several hours on end.

Europeans do not keep their cars as long as Americans, and they don’t care if the car will fall apart at 200,000 miles. By that time it has already been exported to Africa or some other developing country.

A good alternative? Mobil1 full synthetic. (10W30?) Doesn’t break down as readily in heat, flows great in cold, lasts much longer than dino oils, and doesn’t leave sludge behind. I personally would never switch back. 235,000 miles on my original 14 year-old engine and going strong.

Yes, your 325i calls for 20w50 in your climate.

Believe it or not, “the local oil change store” is not the arbiter of what is good for your BMW. (I have three 325i s myself.) Trust what those good German engineers say about your car. They are FAR SMARTER than the “techs” at iffy lube.