I just read that the oil I am using, Castrol Syntec, is NOT a complete synthetic. ack. I've been using it in my 2005 S since I got it new. We are due for an oil change. I am wondering if we should change horses in midstream and move to a royal purple or something similar (I've been told this is bad for the car in the past, but not sure why) or just keep on with the syntec. Any advice would be appreciated!

 

I use mobil 1 .. they have it at Costco & walmart cheap. No issues mixing, just another car myth.

phil.

 

Most syn oils are not total syn any more. Most are group 3 stock and you need group 4 stock to be total syn.
On the other hand, the new SN ratings for oil make it so good you are probably ok with just about any syn labeled SN oil.
M1 is good as are most of the majors.
Switching from one syn to another is not an issue to worry about.

 

That oil is fine imo....you are out of warrenty, so no worries there.
That oil DOES NOT MEET the bmw/mini longlife spec, so i would not leave it in for 15,000 miles, but 7500 is fine...you MIGHT be able to go more, but an oil test should be done, so a change is simpler imo. Mobil 1 euro is the only mainstreem oil that most bigbox stores sell that meets the longlife specs...other mobil1 oils are good, but the euro version is said to have a different base...true syentic, rather than a "upgraded" stock base....and apparently more additives.
i generaly uses the castrol syentic you use, no issues or the mobil1, depending on the sales...and do 7500 mile intervals.....

 

P.S.
The boutique oils....redline, royal purple ,amsol are , etc are all said/advertised as exceeding all specs...but to my knowledge NONE are actually TESTED to meet, and thus displsy on the bottle they meet the bmw/mini specs.....
they are small companies, and i am sure testing is $$, but this same argument sometimes makes me wonder if they have $$ to spend on research and development......

 

I use Mobil-1. Never had any problems...

 

I'm with the others here - I wouldn't get too hung up on Group 3 vs. Group 4 or even meeting the BMW spec unless you're pushing the drain intervals beyond 10K or so. I've been running relatively-cheap and readily-available M1 5W-30 (I wait until Costco has a coupon) since my 2004 was new, changing at about half the 15K intervals recommended by the maintenance system. No problems, very low oil consumption.

OTOH, if it makes you sleep better at night knowing you're giving your car the absolute very best, go for one of the boutique oils or splurge on the M1 Extended Performance. But I doubt it is cost effective to go beyond plain old M1.

As others say, they all mix, so no worries there.

- Mark

 

maybe a little of topic but.... does anyone change weights during different seasons or is it ok to run 5w-30 all the time? in my rx7 i change the oil for each season and when i had the jetta i did the same thing. used different weights for each season. i have never used synthetic so i dont know how it reacts.

 

Current best thoughts is run as low a cold weight as you can stand, 0.
This allows oil to flow when it is most needed, on start-up. There really is no disadvantage to running a 0 weight oil.
I run 0-30 M1 all year. Some prefer the 0-40 because it is group 4 base stock, true syn.