Hi every body
Asda have reduced GTX 10 -40 semi synthetic 4l oil down to £12
its time to service my car
That will cause no damage at all to your engine.
Readily available at Euro Car Parts for under £16 most weeks 
Ah good info thanks, just checked Halfords and they have Mk3 oil on offer too,
Meets all specs required, bargain.
Just bought from Asda 4 litres of Castrol Magnatec 5W-30 Fully Synthetic for £20. It’s API SL and ACEA A5/B5 so top stuff.
Just bought Magnatec 10W-40 A3 B4 API SL/CF ACEA A3/B3 A3/B4 is this OK ; AS BOOK SAYS TO USE 10W-30??? Part synthetic
Sure this has been asked before so please don’t groan!! As the Halfords/Ford offer is so good can I use a fully synthetic in a 1999 Series 2 with 1.8I engine? Thanks, Friar
In a word yes.
Regards Geoff Peace.
Thanks Geoff - as always straight to the point and not capable of misinterpretation. Regards returned, Friar
Buggs
A3/B4 is a a spec for long drain interval engines or direct injection diesel engines both of which tend to be hard on oils. Your 1.8 MX5 is an engine that is quite kind to engine oil and I assume it has an oil cooler. Some of the early cars did not have an oil cooler and in extreme conditions could effect the oil with high temperatures but plenty people in the US have raced the early cars with out oil coolers and used oil analysis of the oils gave little cause for concern.
So if anything the Magnatec is slightly overkill and it is also towards the top of the range of viscosity for a 40 grade oil. Therefore it may give very slightly heavier fuel consumption than 5W/30 or 10W/30.
If your engine has the dreaded tappet clatter caused by poor design of the tappets on the MK1 the Magnatec may tend to cause it to be slightly noisier at startup but it will cause no damage to the engine due to it being towards the thick end of the scale.
Therefore there will be no problem at all with this oil.
The recommendation for a 10W/30 was because at that time up to say 2000, 5W/30 oil was expensive it was only specified if you were going to be in very cold conditions. 10W/30 was much cheaper at it uses less viscosity modifiers so less cost and easily available in the US, therefore that was the main recommendation for an engine oil in non cold areas. Today apart from the US, 10W/30 is difficult to find. You will find it on ebay and in garden machinery stores in the UK but our normal oil is either 5W/30 or 10W/40 and now 5W/40 or 0W40 is not to difficult to find.
So go ahead and use the oil or virtually any oil on the market in an MX5.