The car does 9k a year. Looking to top it up! What grade is best and is fully synthetic a good idea?
I would use a 5w-40 synthetic and you will find those through the link below.
http://www.opieoils.co.uk/c-656-5w-40.aspx
Out of those, the best ones are the Silkolene Pro S, Millers CFS, Motul 300V, Redline and Gulf Competition. The Motul 8100 X-Cess, Gulf Formula G, Fuchs Supersyn and Mobil Synt S are good, cheaper alternatives.
Cheers
Tim
I would use 10W40, I like Shell Helix Plus. I see no massive advantage of a fully synthetic.
Robbie and Oilman advise if you can.
The owners manual for my 99 Mk2 advises a 10W 30 engine oil. You both plus the Castrol and Shell charts advise a 40 grade oil in semi synthetic. I’m aware there is not a hill of beans in it. I also believe if you go into a Mazda dealer to buy Oil, they will supply the Mazda product which they in turn buy from Total and also a 40 grade oil.
Again our 07 Suzuki Jimny is specified in the owners manual as 5W 30 but the dealer at it’s services plus the Shell and Castrol charts point towards a semi synthetic 10W 40.
What is the reason for this or is it just a way to standardise on 10W 40 so that stockists do not have to stock such a wide range of oils.
eddie
Hi Eddie
Most dealers believe that all cars run on a 10w-40. For the cars you have mentioned, it’s okay, but a 5w-40 is better as it will give better cold start protection and over the 5w-30 and 10w-30 will prevent the oil getting to thin if you like to put your foot down. Dealers don’t want to carry a range of oils as it costs money and takes up space.
Dealers tend to use the cheapest oils available and charge the most they can, it’s always best to supply your own. You get a good oil at a better price and you get what you need rather than what they have lying around.
Cheers
Tim
Nombie You do more miles per year, than me but I use Castrol Magnatec no problems.but with some fully syn oils you get the top rattle unitl the oil gets up to the valve train.gear etc go onto www.castrol.com put your car details in and it will tell what castrol oil to use, but keep to the manufaqctures recommended intervals and always use a Mazda oil filter
Alan
Most dealers believe that all cars run on a 10w-40. For the cars you have mentioned, it’s okay, but a 5w-40 is better as it will give better cold start protection and over the 5w-30 and 10w-30 will prevent the oil getting to thin if you like to put your foot down. Dealers don’t want to carry a range of oils as it costs money and takes up space.
Dealers tend to use the cheapest oils available and charge the most they can, it’s always best to supply your own. You get a good oil at a better price and you get what you need rather than what they have lying around.
Tim great reply and to the point.
While I have your ear, what are your thoughts on the Classic Oils from Castrol, Miller , Halfords, Valvoline VR1, etc where they increase the ZDDP from approx 1,000 ppm of a normal 20w 50 that may be used on a Catalyst equipped car. To say 1,400 ppm for the likes of a 1970 Midget or Morris 1000.
Or would you use a more modern oil!
eddie
My two penneth:
I’ve done extensive researching and reading on this subject and have come to the conclusion that 10w/40 Mobil S semi is the favourite for this engine in the UK, and that’s what I shall put in mine.
On later Mk2 cars (2000 onwards) 5w/30 semi is also OK. There is a popular belief that Fully Synthetic gives no advantage if you do regular 6000 mile oil changes, except make your wallet lighter. 
I agree and have used it from new. 10/40 is the Mazda recommended grade but I change my oil every 5000Kilometres. The Magnetec is a definite plus for infrequent users and cold start protection, which is where the major wear takes place for most of us.
Eddie,
Lots of debate about the ZDDP issue. The classic oils do tend to have greater amounts of zddp for extra anti wear but to be honest the only oils with heavily reduced zddp leves are oils that meets API SM the latest API spec. Any oil that carries an API S spec prior to that will have healthy levels of ZDDP. A classic 20w-50 will be fine for the Midget and Morris, equally a good modern synthetic 20w-50 such as the Silkolene Comp 4 20w-50 with is ester content and strong antiwear additive pack will also be ideal.
Cheers
Guy
Interesting, what reasearch have you done? We find the Mobil 10w-40 semi a very popular product too.
However I do have to dissagree with the popular belief, a good quality synthetic will lubricate and protect better then a mineral based oil (this is why mineral oils are used to bed in a new engine, synthetics lubricate too well). So even is you change a good quality semi synthetic every 6k it will still not do as good a job as a quality true synthetic changed at 10k.
Cheers
Guy
I stick by my earlier comments.
Far as I’m concerned the worst thing you can do is change your oil and filter at 10k rather than 6k whether Synthetic or not.
In terms of research I have no ‘Oil qualifications’, the research I have done is to observe the manufacturers recommendations, who spend millions of pounds on engine research and development and should know what Oil to recommend for their engines. Mazda nor Ford specify Full Synthetic or otherwise but only the AP or S specifications. Other information has been gained by discussing the subject widely with other owners on forums etc, asking service technicians what they use and, interestingly, entering my car details into Oil choosing sites (including Opie oils) which all come up differently.
My view therefore, is that these sites will sell what they want to sell the customer and not what the customer really needs!
After 44 years of Car, Van and Motorcycle ownership with 19 different vehicles and doing my own maintenance without an engine failure (one of which covered 120,000 miles) I stick to my belief that Fully Synthetic offers no practical advantage (only a cost disadvantage) if you change the Oil and Filter at around every 6000 miles.
I love all the discussions about the right and wrong oil for a '5. The answer is that there is no answer! The designers of the engine made a recommendation, but that was based on the technology available at the time [late '80s in this case] the world has moved on apace in most things including oil. I would suggest that in a car where the oil is changed every 6k miles, most oils will be ok, so long as they fit the basic spec for a petrol engine. Regarding the 120k miles without a blowup, that’s fairly normal, one of my small Ford diesels did 250k miles run mostly on el cheapo oils, but changed frequently. I use Mobil 1 fully synth 5W50
Keep the discussion going though, maybe one day we will get a definitive answer from someone who has done the necessary real life testing and measurements—
Yes Geoff I agree. The Oil choice is very confusing, aided somewhat I think by these Oil choosing websites (put your reg no in and we’ll tell you what to use). Although the designers of the engine recommended an oil in the 80s I would think that they update that recommendation with each new model or engine change. This may be why we all have some conflicting oil statements in the handbooks.
Diesels do tend to last longer than Petrol engines don’t they? Looked after, a diesel is probably unbreakable. I mentioned my 120k because I did it all myself, the engine was still going strong when I got rid of the car due to the deteriorating state of the upholstery, window rubbers etc.
You use Mobil 1 full synth 5w/50. That’s yet another one. I’m not even sure I’ve seen that in Halfords (UK). The common one is Mobil 1 0w/40.
It is a good discussion but one where I don’t think we’ll ever get consensus.
My 250k Ford finally fell to bits, rotted out from under me despite a lot of welding over the years
. When I was in the UK I used Redline 15W40. It was as clean on the dipstick after 6kmiles as when it was put in. I did wonder if that was a comment on it’s detergent qualities !! My Mobil goes darker after about 4k miles and then doesn’t change colour.—
It is partly down to what the car is used for and how long you want the car to last. We sponsor several cars that are absolutely thrashed and when they take the engine apart at the end of the season, the mechanic is usually surprised to find the engine is in immaculate condition, showing far less wear than others that have being doing a similar thing on what are sold as similar oils.
In modern terms, 120000 miles on an engine is very little, I’ve had two pass 175000 and were fine (one was written off, the other fell apart around the engine), we have a BMW 525i at home that is on 275000, drives like it has 2750miles on the clock and that has been using synthetic oil as BMW generally recommend.
Why would manufacturers want to sell you the ideal oil for the car? If the car goes on for ever, you don’t buy parts from them or eventually a new car. Many Ford oils are designed to break down over the service period from a 5w-30 to a thinner grade, so the fuel economy gets marginally better, but there is less engine protection. All they want to do is get the car through the warranty period and then for things to go wrong.
We sell people what we believe is best for the car/bike/boat. We aren’t limited by availability of an oil grade as we stock several brands, so if you checked the Castrol website, they may have given a different answer as they don’t make an oil in the ideal grade. Certain other places honestly just don’t know the answer of what you need. One of the largest online motor parts shops refers people to us as oils are what we are experts in.
Yes and I believe that this is the crux of a lot of owners confusion. Too many different ideas/recomendations!
When I was looking for what Oil and Viscosity to buy I got totally confused. Years ago your mind was made up for you, it was 20/50 multigrade and that was that. Today we have 3 types (Mineral, Semi and Fully Synthetic) countless viscosity combinations and many brands. ie. like everything today there is too much choice promoted by manufacturers competition.
I virtually gave up and just went with the Handbook recomendation of 10w/40. As 10w/40 seems to be Semi and Mobil a good brand, I settled for that.
As for the Oil change frequency, I beleive it essential to change the Oil and Filter at short mileage (6000 or less) intervals on MX5s, (1) because of the small Oil Filter used and (2) because many owners are infrequent users of there cars doing only short journeys particulary in the Winter (when mine rarely gets used ) contributing to that yellow froth contamination you get around the filler cap.
I expect your going to tell me the above is even more of a reason to use Full Synth! 
EDIT: Perhaps you could advise on the theory that Full Synth must not be used if the engine never had it from new. Like many second hand owners I can’t tell what has been used before!
“yellow froth contamination” 
I switched to mobil 1 0w40 on both our mk1 and mk2. Not sure its any better or worse than other options, but it is definate that the mk1 which used to suffer HLA clatter if left for a week or so no longer does, so in my mind at least there is some benefit. Have had no issues with oil leaks or others horrors that you are supposed to suffer when using fully sythetic, so I will continue to use it…