Mazda Xedos Oil Question

[SEC]

First apologies for the long post.

I have recently purchased a 97-model Mazda Xedos 6 2.0 v6 (Eunos 500 in some markets). I believe the engine is related to the Ford Duratec series of engines.

The handbooks indicates that 10W30 engine oil may be used for temperatures from -20degreesC upwards, and that 5W30 may be used from 0degreesC downwards. I have some questions about this:

1) If both oil grades have 30-weight viscosity when hot, why can the 5W30 not be used all the year round? (which I later found out iswhat the previous owner did) I understand that the 5W30 will be thinner when cold - does this preclude it lubricating properly in summer temperatures during engine warm-up?

2) I have used Mobil 1 0W40 successfully in a Mazda MX5 (Miata), BMW 325i and Audi A6 with what appear to me to be good results (144, 135, 152k miles respectively) What would be the implications of using a 40-weight oil like this in the Mazda V6? - I mean in terms of long-term durability rather than rough running or noise.

3) We have a rather limited selection of oils here as compared to what appears to be the case in the USA. Of what is available, I am considering the following possibilities:

10W30: only available locally as a very cheap, non-brand-name oil.
5W30: Shell Ultra, sythetic base
0W30 or 5W30: Castrol Syntec or Magnatec
0W40: Mobil 1

I am somewhat confused as to how best to proceed, and would appreciate any advice anyone is able to give.

Thanks in advance and apologies again for the long post.
SEC.

 

[Losiho]

Firstly, the engine is a Mazda K-series V6, used in several models such as the Eunos 30X/ MX-3, MX-6, 626, 323 and Eunos 800. It is definitely NOT a Ford Duratech engine, it's all Mazda, before Ford got their grubby hands on it.

I'm going to try both Motul 8100 0w40 and Mobil 1 0w40 for my next fills in my MX-6. I currently have Castrol Formula R / Syntec 5w30 which seems to be working ok. I would try the Castrol or Shell oils in your case, or the M1 if you want a full synth (which is recommended for that engine).

 

[haley10]

These recommendations are a bit strange, but based on many sub-standard oils in many countries they may make some sense.

I would absolutley trust Castrol in either grade to work fine.

There is no reason, that a quality 0-30 or 5-30 cannot be run year 'round.

In fact the German made Castrol 0W-30 is much sought after in Canada and the USA. It's great stuff.

A 40 wt. would be ok, but not not really needed in UK.

I'd check out the Castrol if it were me. M1 0W-40 is good too, but I would not pay a premium for it. It will thin out, too.

I'd run Syntec or M1 year ' round!! I do anyway.