Mazda Xedos Oil Question

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Feb 27, 2004
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.
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).
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. [Big Grin] [Big Grin] [Big Grin]
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