Which oil to use? Castrol 5W30 or M1 0W40?

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Jun 17, 2003
Montreal, Canada

relatively new here, and as I am overwhelmed with the amount of info available in this forum, I still am undecided as to which oil to put in my car.

I drive a 1999 BMW 328i. I happen to live in Montreal, where the winters are deadly cold (-30 Celcius happens often enough) and summers get hot enough (30 Celcius once again).

For the winter I use 0W30, otherwise the VANOS jams up and triggers a Check Engine light. The 0W30 is from Castrol, but I have no quams using Mobil 1 if it's better (or cleaner, etc.).

Now for the 6 months of the year when we're not submerged in snow and hiding in our igloos
I'm not sure wether i should continue using Castrol's 5W30 (OEM recommended - but I don't really trust BMW's recommendations as they tend to make you end up having to buy a new car) or switch to Mobil 1's 0W40 (which is also a approved BMW oil).

I've performed searches, but I haven't really been able to assess what the main differences are between Castrol 5W30 and M1 0W40, their pros and cons.

Thanks guys.


I think one of the most important things you need to know, surtout donné les hivers que vous éprouvez, is that Castrol Syntec 5W-30 is not a REAL synthetic; it is a Group III hydrocracked oil with some Group IV synthetic blended in. Conversely, Mobil 1 0W-40 IS a true synthetic as is the German version of Castrol 0W-30 now in limited availability in
and the
. My recommendation would be, in order of merit and availability M1 0W-40 and then German Castrol 0W-30.

Merci de l'accueil si chaleureux.
Thanks for putting my concerns to rest.

Now comes the issue of finding M1 here in Montreal. Otherwise.... Border Run.

You mention that there is a German Castrol 0W30. This is going to sound like a stupid question (because it is) but how do I go about finding out if the Castrol 0W30 I am buying (this fall/winter) is the German version or not.

What are your feelings towards M1's 0W30?

Lastly, I also have a 1995 BMW 740il that I am taking care of. The 'recommended' oil is Castrol 5W50. What would be a likely substitute from M1 (if any exists) 10W40, 15W50 ?

Once again merci pour toute l'aide que tu m'as offert.

Merci de l'accueil si chaleureux

ahhh, French...

I'll give you my 2 cents. Castrol 0w-30 German, or Mobil 1 0w-40 are good oils. I don't like Mobil 1 0w-30. I had consumption issues with it. Not sure why. If you car calls for Castrol 5w-50, I'd run Mobil 1 15w-50. It's a very good oil and should do well in the summer months. Winter though is different due to the 15w....

[ July 21, 2003, 09:10 PM: Message edited by: buster ]

Originally posted by Asmodeus:

You mention that there is a German Castrol 0W30. This is going to sound like a stupid question (because it is) but how do I go about finding out if the Castrol 0W30 I am buying (this fall/winter) is the German version or not.

What are your feelings towards M1's 0W30?

Lastly, I also have a 1995 BMW 740il that I am taking care of. The 'recommended' oil is Castrol 5W50. What would be a likely substitute from M1 (if any exists) 10W40, 15W50 ?

Once again merci pour toute l'aide que tu m'as offert.

de rien...c'est mon plaisir vous aidez

To recognize the German Castrol: (1) the box (case) and each bottle will have the 0W-30 rating in red block or background...if it is in a yellow background you do not want it; (2) on the box and on each bottle it will say "Made in Germany Imported by Castol North America, Inc." From what I am hearing Wal-Mart in Canada carries it. I would look soon if you need to do a change in the near future because once the "cognoscenti" start hearing about it, and as you get closer to Fall/Winter, it may go off the shelves quickly. It seems to be in marginal supply right now...I am buying it when I can find it for oil changes still pretty far in the future. (According to Castrol availability should improve if the product sells well.)

I am not keen on M1 0W30 not because I think it is a bad oil (I used it with great success for a year and a half). I just like the specs of 0W-40 better.

Your 740 question is the toughest. I think M1 0W-40 would work well in that application but I also think some Bimmers like the heavier weights. If you were in Southern California I'd recommend M1 15-50. If you could get it in la belle, mais froid, Québec, I'd recommend M1 5W50 (not available in U.S. either). So I think you have two choices, see if your BMW dealer has Castrol TWS 10W60 (you may have sticker shock from the price) or go with Castrol 5W-50, even though it is not REAL synthetic and change it every 4K miles or so.
Asmodeus, I think the best oil to use in the BMW 328i would be the Castrol Syntec 0W-30. This oil has not been out too long and there may be some of the old Castrol Syntec 0W-30 ACEA A1 rated oil still on the store shelves so be sure to look at the back of the bottle and look for ACEA A3,B3 and B4. This is in addition to the Made in Germany and of course the 0W-30 written in red not yellow. I like the specs of this oil more than the specs for Mobil 1 0W-40. I also believe the Mobil 1 0W-40 is hard to find in Canada while the Castrol Syntec 0W-30 is available at Walmart.

For the BMW 740il I would suggest that you stay with the Castrol Syntec 5W-50. The Castrol TWS 10W-60 would be a good alternative choice but it is very expensive. I would stay away from the 15W-50. Any 5W-40 ACEA A3,B3 motor oil would also work well in the winter but would likely give you higher oil consuption.
I have used M1 0w-40 in my BMW Z3 2.8 with excellent results. It has now been changed to Mobil Delvac 1, the same as in my Subaru Outback 2.5

I have had only bad results from Castrol SLX ( German 0w-30 ) and I would NEVER use it again

Over nearly 25 years I have used Castrol R synthetic 10w-50 - now a modern specced 10w-60 It is simply too expensive

Sin City: Thanks for the info, I just wrote down all of the specifications to look for, as I will swing by Wallmart today to see if I can find a case of the stuff. Start stock piling early.

Doug Hillary: What is Mobil Delvac 1 ? I perused the Mobil1 website (.ca and .com) but didn't seem to find it. Perhaps I was looking in the wrong places.

Also, can the issues you've had with SLX were they with your Z3? Fact of the matter is that the M52 engine for the E46 (323,328) requires 0W30 in the winter. Which would you suggest? Also, when was the last time you used SLX? I take it that they 'upgrade' their product every year, right?

FYI, here in Montreal, Castrol TWS is $20 (CDN) per liter. Given the conversion rate that's close to $0.50 (USD)/ Gallon. j/k

Once again, thanks to all of you for helping me out. Peeps in other forums just kept on telling me: "use what it says on the engine sticker OR have fun damaging your pistons (???)"

Do you gents know of a site that explains in dummy terms what UOA is, and what these ACEA (etc) standards mean (in real life application would be nice)?


Take a look at the UOA forum on this website; hopefully, you will find all you need to know there. In a nutshell, a UOA is a peek into your engine through analysis of your motor oil. The UOA will tell you what wear metals are prevalent in your motor, will detect moisture and anti-freeze (hopefully none of the latter and little of the former), will tell you how well your oil is holding up (viscosity/shearing, Total Base Number [how much acid-neutralizing capability your oil has left], the amount of solids in suspension, etc). It is best to use a company that gives you good analysis along with the raw data (like Blackstone on this website) and we have a guy associated with this site, Terry Dyson, who will provide you expert personalized analysis if you hire his services. This is important. For example, you might get your report back and the amount of copper in the oil is "high" and you panic. Well, if you have selected Terry to do your analysis, he might say, "This is normal for this particular make of engine with this many miles on it." If it is not normal, he will tell you.

Regarding ACEA, go to www.acea.be, pick the "Publications" option in the list on the left on the first screen and then pick "European Oil Sequences 2002 Revised (18/06/2002 - PDF" from the list of pubs. You will find a 13 page document that will tell you, I think in very understandable terms, what you need to know about ACEA.

Ahhh, les Habitants, quand recevra-t-il mieux?
Mobil Delvac 1 is a 5w-40 diesel oil and often mentioned on this board. It is most suitable for petrol engines. There are many references. It is not mentioned in the Mobil 1 site

The problems I had with Castrol's SLX was in a 1.8 VW engine in the period 97-2001. I used it in a Ford Explorer V6 as well - it performed a little better in this vehicle
It will never go into another car of mine
It was a Dealers's "warranty" fill in my wife's 2001 VW Golf - it was changed at 5000 kms to Mobil 1 0w-40

My BMW has only been on Mobil 1 0w-40 and now Delvac 1. This oil is the oil used by most BMW Dealers in Australia

As the pour point of M1 10w-30, 0w-40 and Delvac 1 5w-40 are/were similar it ( Delvac 1 ) should be OK in your car year round

Interesting, I didn't know that some Diesel Engine Oils were suitable for Gasoline engines.

Thanks for the info on UOA and ACEA (reading it right now), i'll be sure to inquire more once i've digested the material.

Pscholte: On ne recevra jamais du meilleur au Canada. lol.

On the bright side, I did pick up 11 liters of the German Castrol 0W30 for this winter.

Doug Hillary: I live approximately 10 Km away from my BMW Dealership, and I do my own servicing aswell.

I do have another question which comes to mind. From the reading I have been doing thus far, I understand that Mobil 1 is 'cleaner' than Castrol (0W40 vs 5W30). As I will be changing to 0W40 next oil change, are there any recommendations on how to remove most of the slop in my engine before putting in the Mobil 1?

What are your views on using an Engine Flush? As for cleaning systems, I'm using the Z-Max and during my stages of oil ignorance I was happy with Z-Max. Now i'm reading about AutoRx. Just need to find if it's available in Canada.

Thanks again for all the help guys.
YZF150 - After being a long term ( 20 yrs odd )user of Castrol R synthetic I started the 1.8 VW on the then new ( to OZ )SLX. It was a very little used car and after the second oil change we noticed the oil had thickened somewhat. This car had a oil temp gauge and at times the oil temp was up around 120C ( permitted in the handbook ). Then it climbed higher. We then lost oil pressure and finally the engine was inspected under warranty. We ( the Dealer, VW Service Rep. and I )concluded that the engine had prematurely varnished and sludged causing the problem. The Dealer and Rep. indicated other SLX users had the same problem unless the oil was changed at a much greater frequency than recommended. I had the same problems with Castrol petrol oils many many years ago. But their diesel oils RX Super, Enduro LD have been excellent

The Explorer never had this ( SLX ) problem - it was a daily user though. It was then put on to M1 and so was the 1.8 VW - until it was sold without further problem. In all my experience I had never had a VW engine do this - even when in low utilisation.

Asmodeus - What we do in the trucking business - both engine suppliers and owners - and I have done with petrol engines too,is the following

Select a CH4/CI Diesel oil of the correct viscosity - say 15w-40 - and do at least one "quick cycle" oil change. Example: Get the engine hot - prolonged and up to higher revs etc. - a few times in the period, running only about 1000 kms or so in total. Then change the oil and filter.You could do this another time too if you wish.
No diesel truck engine makers I know of here use other than this process - it is cheap and effective

And it works well in petrol engines too


I have got AutoRx in my motor right now (Ford Taurus 3.0L with apprx 100K). Folks around here will tell you it's the best thing going to get a clean engine. Go to the "Suppport Our Site" Forum on the "Forum Home" page, enter that forum and follow the AutoRx links. You can order on-line (special now is 2 bottles @ $24.95 each and get a 3rd bottle for $5.00). There are two regimen: 1 for cars 100K. It's all explained.

Bonne chance!

[ July 22, 2003, 10:19 PM: Message edited by: pscholte ]

On the bottom of the bottles of that German Castrol are inkjetted lot and production numbers and times. Please list the different strings of numbers found on those 11 containers.

Example: M023386B 784A1 2002
Doug I was very surprised to see old SLX 0W30 at AutoPro yesterday around $65 for 5 litres. Even considered it for my Outback in a moment of temporary insanity. The Formula R 10W60 was there and 5W30 but no 0W40. I'm still not decided on which oil to be used with RX maint dose but leaning towards Visco 5000 or M1 Supersyn 10W30 (appears 5W30 wont be imported). Redline 5W30, which I used after D1 would be my choice buy just too exy for me now. Still with D1 in all your vehicles hard to go wrong IMO.
9 of the bottles were:

M030426B T/W1240607

2 of the bottles had:

ME30426B T/W1240607 But it could have been a mispring and the E was meant to be a 0
Thank you.

Yes, based on what I've seen so far, I'd say that the lettering was somewhat scuffed on those two bottles.

Hello Sprintman - yes, there is a lot of "old" Castrol SLx and Formula R 10w-60 around OZ. I have seen it from Mackay to Bisbane at varios outlets

I have seen 5lts of "old" SLX priced at $120!!!
And "old" 10w-60 at $91!!

Since the BP takeover of Castrol, the Castrol side of things sure are a Rat's bottom!

If I did not have access to Delvac 1 so easily I probably not use it. It simply is not sold "retail" by ExxonMobil - I wonder why
One reason is the constant "squabling" between Lube and Fuel Divisions and the Exxon "influence"

My Outback has now done 13000kms on Del 1 at about 1/4 the oil consumption of M1 10w-30
It is a happy application
I would not mind betting that M1 10w-30 may be dropped here in favour of M1 0w-40 - a great oil

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