I have had my 1993 Mk1 for a couple of months now and I am about to take it it in for a full service and cambelt change. I was quoted £150 which I thought was a really good price.
When I bought it the chap who owned it told me he used fully synthetic oil. I am keen to continue using fully synthetic as that is what the car is now ‘used to’.
When I spoke to the garage that will be doing the service next week they said they would use 10-40 Castrol oil and said that is what they usually put in MX5’s. It was only today that I realised that 10-40 oil seems to be quite hard to come by in fully synthetic form. Although I told the garage I wanted fully synthetic I may not have emphasised that enough and they could well have just quoted me for semi-synthetic 10-40. It appears that 5-40 oil is what is the nearest to 10-40 that is commonly available in fully synthetic form.
My questions are:
If I ask the garage to put in 5-40 fully synthetic (assuming they have that in stock and against what they advised) I assume this will be perfectly adequate for a 1993 MX5 and will make little to no difference?
Even though the car is running fully synthetic could I just switch to using semi-synthetic which the garage has in stock and be in-line with what they advised?
I’m quite new to oils so please forgive my ignorance
Thanks for your reply Keith. I will have a chat with the garage and see what the cost would be for the pulleys, tensioners and water pump. I have some other issues to get sorted with the car that are rather urgent so the price will dictate if I can afford to get those bits done as well - I hope so!
Thanks for your advice on the oil. I am certainly going to try to get them to put in 5-40 fully synthetic but if they don’t have that oil can I switch to semi-synthetic from fully synthetic? I assume it would be okay but I don’t know if once you have gone fully synthetic it’s best to continue that route?
For those who do not sleep at night you can log on to the bobistheoilguy site where people post used oil analysis of engine oil taken from the car sumps when drained.
While I have no trouble sleeping at night, I have read through lots of UOA for MX5’s and Miata’s mostly cars up to 2005.
The majority of these posted analysis sheets mostly from the labs of Blackstone Labs show MX5 engines UOA that have used 5W/30 10w/30 and 10W/40 oils.
I can see no increases or decreases in ware metal content in these samples for the different viscosities of oil used.
The Iron, CU and Aluminium traces are wear metals.
Therefore as there are no increases in wear metals between the different viscosities I get confused by remarks made by Richard among others as no increase in wear metals over say 30k miles means no downside to using 30 rated oils apart from probably a higher oil consumption but nothing of any significance when I have used them long term over 40 grade oils but YMMV.
While certain modern engines specify oils that can only be made from synthetic base oil for instance 0W/20 and the newer 0W/16 not as yet on the market both 5W/40 and 10W/40 do not need synthetic base oils to produce the oil to the A3/B4 ASEA specifications.
I can assure you that engines do not either know or have any memory that they have used or have used synthetic oils either now or in the past.
My checking has shown that the engines will be happy on either a 5W/40 or 10W/40. Due to the softness of the MX5 engine to oils, either will be just fine.
Most 10W/40 oils including Magnatec and GTX are semi synthetic and the majority of the newer 5/W40 oils use synthetic base oils.
Therefore just put it into the garage and let them use the oil they have in stock and do not worry about it.
Thanks for all the replies. Interesting to hear the engines have no memory of oils they have used - that’s great.
As suggested I will just let the garage crack-on with 10w-40 semi-synthetic (Castol Magnatec I believe) and put the issue to bed. It’s handy to use a cheaper oil anyway and one that this garage will know well rather then my own specific request of 5w-40.
Many thanks for resolving this query for me, you have been a big help to a newbie
While I am asking about oils. The guy I got it from mentioned he put fluid in the oil to prevent tappet noise (Wynns I believe?). Would this have to be done during a service or can it just be poured in there as and when anything like that rears its head?
I did the same with my 1990 Roadster back in 2000, end of startup rattle for good. Always used semi synth oil, changed every 5k miles. Still going strong when I saw it the other day
I believe currently the car has Wynns in the oil so based upon what you have done then I guess I don’t need to add it to the oil now and should just get the oil change and then see how it goes? Is the stuff something you only need to add from time to time or should be added to old oil each time you are about to get it changed?
If that is the case then my car shouldn’t need the treatment for another year until this fresh oil I am about to get is ready to be changed on the annual service.
Hi all, my first post so please be gentle with me. I changed the oil and filter on my 94 1.8 Eunos last week and put in Halfords 5W 30 semi synthetic ( Ford ) oil as that’s what the guy at Halfords recommended. Now I’ve read a couple of threads on here it seems 5 30 oil is for the mk3 and above and the mk1s should use 10 40. Do I need to replace the oil I’ve just put in with 10 40 or will it be okay until the next time? I do about 3000 miles a year and don’t drive it very hard. Also if I do have to change the oil I’m assuming I won’t have to replace the filter as its new, would you agree? Many thanks. David.
I’d just run it with what you have tbh. Only, don’t make a long term habit of it.
Agree about filter…if you take the decision over the next 100 miles or so to drain & fill, unusually I’d just let the filter stay as well… provided you do it quick.
