when to use Castrol Syntec 0w-30 vs. Mobil1 0w-40?

[motuman]

Hey everyone, I'm new to the forum but not new too engines and mechanics, etc.

Here the situation...I currently have 4 cars that I maintain myself, and for the sake of convenience it would be nice if I could use the same oil in all 4. There are (3) BMW's V8's (with between 63K and 164K miles) and one Subaru 2.5 STi turbo powered, street legal dune buggy.

• I currently use Mobil 1 0w-40, because that's what BMW specs and that's what I can easily get.
• I live in SoCal, so no real cold temps.
• I only put between 4k to 8K miles per year on the cars, lot's of short trips. (less on the buggy)
• I'm generally easy on my machinery, but do occasionally push them to their potential.
• I usually change the oil between 6K and 7K miles. (1K - 2k on the buggy)
• I cannot get Castrol Syntec 0w-30 (GC) locally, I would have to mail-order it or pick it up on road trips.

At the risk of opening a can of worms - Is there any reason for me to spend the extra time/expense of obtaining and using the Castrol Syntec 0w-30 (GC)?

It would be nice to use the same oil on all 4 cars, but I would certainly be willing to use something different on the buggy (Subaru STi powered). When driven in the sand that engine see extreme duty....i.e. high loads, high temps, etc. While it is usually driven on the street, when I do go offroad I change the oil after two or three of trips (over concerns over dust ingestion). The more frequent oil changes make it less attractive for a high $$ oil, like Amsoil, etc, but I would like to get all the protection I could get. The factory STi oil is 5w-30, but I originally thought using the Mobil 0w-40 couldn't hurt with the extra viscosity for the high temps, etc, and lower viscosity for cold starts. (After some quick reading of the forums, it sounds like Mobil 1 0w-40 isn't really 40 weight for long).

So what do you think, Mobil 1 0w-40 vs. Castrol 0w-30 vs. ???, and what about the same oil for all 4 cars?

Thanks...

 

[Quattro Pete]

Originally Posted By: motuman

At the risk of opening a can of worms - Is there any reason for me to spend the extra time/expense of obtaining and using the Castrol Syntec 0w-30 (GC)?

No.

The two oils are nearly identical in terms of specs and performance. I would not go out of my way to choose one over the other.

Another oil you may want to consider would be Shell Rotella T 5w-40. It's readily available and does well in Euro and turbo applications.

Quote:


and what about the same oil for all 4 cars?


I see no problem.

Welcome to BITOG by the way.

Which specific BMW models do you own?

 

[Audi Junkie]

Easy, since you like Mobil, Mobil 1 10w-40 Hi-Miles for the buggy, due to the dirt in the air, and Mobil 1 10w-30 Hi-Miles for everything else.

Edit your change schedule to once a year.

 

[sicko]

Since you're happy with the M1 0w-40 I see no reason to go out of your way to get GC (BTW, b/c you're new I wanted to make sure you're aware that the GC means German Castrol, and is the 0w-30 Syntec that says Made In Germany on the bottle, it is different than the US made Syntec 0w-30).

M1 0w-40 is a quality oil should have all the certifications your vehicles require. There's no reason in my mind to switch to anything else. It works in all the vehicles so go for it. Even the Subaru which they say 5w-30 seems to love thicker oils, which is why a lot of Subaru owners use GC b/c it's a very thick 5w-30 at temps. But even the Subaru will probably love the M1 0w-40 since it's not that thick of a 40 weight

 

[daman]

I agree both hare outstanding oils that will serve you well take your pick and go with one, the Mobil may be easier to find.

 

[motuman]

Originally Posted By: sicko
b/c you're new I wanted to make sure you're aware that the GC means German Castrol, and is the 0w-30 Syntec that says Made In Germany on the bottle


yep, that's the one I am asking about. checked that out before I posted...

 

[motuman]

Originally Posted By: Quattro Pete

Which specific BMW models do you own?


1995 540i M-Sport (one of 200 imported)
1999 540iT (sport wagon)
2004 X5 4.4 Sport

BTW - I picked up the 1995 540i M-Sport with 148K on the clock. The vehicle had BMW brand synthetic oil (whatever that really is) most of it's early life, then "whatever was on the shelf" from about 100K to 148K. I pulled the oil pan when I first got the car and I could have swore the engine had no more then 25K. From what I could see the bottom end was squeaky clean, NO gunk and almost no varnish in the pan. I used Mobil 1 0w-40 starting with my first oil change and did notice some oil usage. After a couple of thousand miles, however, it "tightened up"?? and I haven't had to add between fills. Not sure, but I thought I heard something about the this happening when switching to full synthetic on a higher mileage motor.

 

[motuman]

BTW - This test seems to pop up a lot

[non-sponsor link]

Is this basically an add for Amsoil?

 

[d00df00d]

Originally Posted By: motuman
BMW brand synthetic oil (whatever that really is)

It's a custom blend by Castrol for BMW. Good stuff.


Originally Posted By: motuman
I used Mobil 1 0w-40 starting with my first oil change and did notice some oil usage. After a couple of thousand miles, however, it "tightened up"?? and I haven't had to add between fills. Not sure, but I thought I heard something about the this happening when switching to full synthetic on a higher mileage motor.

This isn't specific to full synthetics. It's just something that happens often when you switch oils. The new oil basically has to wash away all the films that were built up by the old one and then lay down its own films. This process sometimes causes consumption. Nothing to worry about.

It is a pretty good reason to stick to one oil, though.

 

[d00df00d]

Originally Posted By: motuman
BTW - This test seems to pop up a lot

http://www.performanceoilnews.com/oils_against_oils.shtml

Is this basically an add for Amsoil?

Yup.

There's no reason to believe the test was rigged or anything, but I wouldn't rely on it to pick an oil.

 

[KW]

M1 0W40 in the BMW's and Rotella T 5W40 in the dune buggy.

 

[shpankey]

Originally Posted By: Quattro Pete
Another oil you may want to consider would be Shell Rotella T 5w-40. It's readily available and does well in Euro and turbo applications.


IAWTP

The Scooby in particular absolutely LOVES this oil!

The 0w-40 M1 you're using is awesome oil too though. So is the GC. lol If those are your choices then take solace in the fact that you cannot make a poor decision.

 

[AntiMatic]

No. Use the 0W-40.

 

[CATERHAM]

Originally Posted By: motuman
BTW - This test seems to pop up a lot

http://www.performanceoilnews.com/oils_against_oils.shtml

Is this basically an add for Amsoil?


That link contains a ton of oil myths.

BTW, GC 0W-30 is not lighter at start-up than a 5W-30 unless the temp' is below 50F. With M1 0W-40 the temps have to be well below freezing to benefit from the 0W rating.

Yes stick with the M1 0W-40 and I wouldn't use a 5W-40 which is significantly heavier.

 

[Craig in Canada]

If the BMWs I've maintained (M52, M52TU, M62 and M62TU engines) were in SoCal, I'd probably have dino HDEO 15W40 in them and change at a suitable interval. If I wanted extended drain or felt fanatical about synthetic then I'd use a 5W40 syn. Rotella is probably a good choice for both grades.

Considering that BMWs tend to like oil on the thick side and Rotella 5W40 is recorded as working very well in the STi, that would probably be my pick as a single "fleet" oil in SoCal.

 

[Audi Junkie]

Originally Posted By: CATERHAM


BTW, GC 0W-30 is not lighter at start-up than a 5W-30 unless the temp' is below 50F.


No, it's thicker as far down as you want to check.

 

[CATERHAM]

Originally Posted By: Audi Junkie
Originally Posted By: CATERHAM


BTW, GC 0W-30 is not lighter at start-up than a 5W-30 unless the temp' is below 50F.


No, it's thicker as far down as you want to check.


Plug the vis spec's into the Widman Viscosity Chart and you'll find GC becomes relatively lighter than a typical 5W-30 (M1) as the temps drop below approximately 10C, and the advantage increases the lower you go.

 

[Geo_Prizm]

Originally Posted By: sicko
Since you're happy with the M1 0w-40 I see no reason to go out of your way to get GC (BTW, b/c you're new I wanted to make sure you're aware that the GC means German Castrol, and is the 0w-30 Syntec that says Made In Germany on the bottle, it is different than the US made Syntec 0w-30).

M1 0w-40 is a quality oil should have all the certifications your vehicles require. There's no reason in my mind to switch to anything else. It works in all the vehicles so go for it. Even the Subaru which they say 5w-30 seems to love thicker oils, which is why a lot of Subaru owners use GC b/c it's a very thick 5w-30 at temps. But even the Subaru will probably love the M1 0w-40 since it's not that thick of a 40 weight


Is there a US made Castrol Syntec 0W-30? I have not seen it anywhere.

 

[d00df00d]

Originally Posted By: Geo_Prizm
Is there a US made Castrol Syntec 0W-30? I have not seen it anywhere.

There was at one time, but that was years ago.

 

[sangyup81]

Originally Posted By: motuman
Is there any reason for me to spend the extra time/expense of obtaining and using the Castrol Syntec 0w-30 (GC)?


We tend to consider GC and M1 0w40 to be about equal

Originally Posted By: motuman
I originally thought using the Mobil 0w-40 couldn't hurt with the extra viscosity for the high temps, etc, and lower viscosity for cold starts.


Actually, M1 0w40 has higher cold viscosity (measured at 40C) but still has better cold weather performance according to a cold cranking test than a 5w30