GroundRat

Good day to all!

Question: Due to the age of the vehicle, should I/could I use a different weight oil, such as 10W-60 or 0W-40? I don't have a problem using what the manual recommends, but I see varying comments about using different weight oils in cars that are older.

Background: I've been using 5W-30 Castrol Edge (Full Synthetic) in my 2003 525i E39 (186K miles, American Spec). Owners manual instructs me to use either 5W-30 or 5W-40. Oil is changed religiously every 5K miles or 5 months, whichever happens first along with using a Mann oil filter. The engine runs fine and I don't have problems accelerating. Long trips on the autobahn yield 20+ mpg (car is American specs) while traveling at the speed limits when posted (130kph / 81mph). Usually don't go above 90mph because I do like to enjoy some scenery being in Germany. Most driving is done with the usual safety-minded acceleration vs. driving in the left lane at break-neck speeds.

Appreciate any suggestions and/or references. Have researched oil comments on this site, but some info seems dated....interested in seeing the current mindset on engine oil.

Note: I live near an Air Force installation and buy oil on base. The usual brands are Castrol, Mobil 1, Pennzoil and Royal Purple. I use Castrol because, and don't laugh, the oil cap on the engine says "Castrol." There are other brands offered on the economy (meaning "off base"), but the price for 1 liter is 22 Euros (about $24.50 per 1.06 qts!)

Thank you in advance,
GroundRat

JayArras

You're doing all of the right things. 5W30 is fine. Some people put in heavier weight oil because they think it will retard leaks. It won't. Continue to use the full-synthetic. Castrol used to be the official BMW OEM oil. Now I think they're gone to someone else. I use Mobil1 because it's more readily available and often goes on sale. (Plus, I own some Exxon stock, lol!)

Goz007

also depends on your conditions & kms/mls traveled, the biggest advantage of 5w30 is that the car will get better fuel economy, but were iam(Australia) & the high temperatures we endure down here + the fact that my m54 has traveled 300k i prefefer 5w40, ive recently been tossing up the idea of going to 5w50 or 5w60

FormerE30Owner

Stay with the 5w40. In fact, under the conditions that you are describing, I would go with a 10w40 synthetic. Once the engine is up to operating temperature, it doesn't "know" the outside temperature conditions and the higher viscosity at 50 or 60 might even inhibit oil flow. The lower number (5w) is really for cold start conditions, to ensure that there is oil flow at the lower temperatures and the lower number isn't necessary for the cold start conditions you are describing.