Hi all.
I’ve had a quick look through posts here, and most of the relevant ones are pretty old, and time and knowledge has moved on.
So question is, does the MK2.5 VVT engine prefer 5w30 or 10w40? Or even, subs other grade?
I know about cold and hot viscosity etc, and for daily use I reckon it would make not a jot of real world difference, but for those people that have run one of these engines for a while, have you found that oil use, cold start, tappet noise etc etc is better or worse with either grade? Ours had hardly been run in, with only 40k on the clock.
It’s my wife’s car, so sadly it’s unlikely to hit the track and get to temperatures where the 40 ( or 50 to 60!) would be significant! 
Cheers!!
TBH, tappet noise is/was the preserve of the Mk1 engines being pressured self adjusting (?) oil buckets.
5-30 you will be fine.
I run one of each, a Mk1 '93 vintage and a Mk2.5 which has solid lifters & does not do tappety even from winter cold. I vary rarely even get intitial Mk1 tappety tunes, which only lasts a minute.
Having said that, I do an oil change every 5k or one year whichever happens, have always used GTX Liquid Engineering (NOT Magnatec),and the oil usually drains just beginning to loose it’s honey colour. I give these drains to a neighbour for his old work vans…so it’s not wasted. Not my best advice but he’s been happy for 16 years!
It’s good to keep those engines well lubed, and get regular runs as the oil control rings do not like getting gummed up. Our 108,000 mile Sport runs like a watch and burns nothing but petrol. I’ve never bothered about using other oils…Castrol has been fine for me for 16 years but…opinions will differ!
And trust me, both of them get a good Italian Tune up… 
I do not think, nor have I found, that 5/30 or 10/40 ever made a difference. I even ran standard Castrol in a 3.1 Capri Burton-Vulcan and a monster of an Opel Monza 3ltr Courteney Turbo without any issues…
Really a Mx5 mill is never going to tax a proper top drawer engine oil of any label…unless Force Inducted of which I know nowt.
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I used to use 10W40 in mine but one of the garages recommended 5W30. Something to do with the operation of the VVT system. Sorry, I can’t remember the details. Certainly the engine runs lovely and I’ve never had a problem since I switched. Ours has done 50K miles.
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I’ve been using 5-30 in my 02 NBFL for years now. Magnatec 5-30 A5 to be precise. The handbook has a choice of 2 grades, the other one is harder to find.
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VVT pressure system is operated via rather narrowish oilways as I recall in a faraway galaxy. Oi fink…
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I use Mobil Super 2000 10W-40 Semi Synthetic as it is recommended that semi-synthetic is best for all Mk2’s
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Thanks all, kinda as I thought.