I know engine oil has been done to death, so please forgive me for starting another thread on this.
I read on MX5parts…
“Please note that Mobil 1 0w-40 [fully synthetic upgrade] can be used in Mk 1’s however in higher
mileage engines which have not been used to synthetic oils previously
then because of the oils detergency some older deposits can be removed
quickly and there is a potential for brief oilway blockages which will
mean that the lubrication of vital parts could be impaired.”
Assuming this is true, can the effects cause permanant damage? My engine has done over 100k miles. I was going to use standard mineral oil for now to be on the safe side.
Ok, I will have a proper look through my service history when I get home, and see if there’s any mention of which oil has been used exactly. So did yours always use mineral oil before you switched to semi? How many miles were on the clock?
This is the thing; I usually use fully-synthetic in my cars, but this is an older engine with over 100k miles, and it’s probably been thrashed - just want to get as much life out of it as possible.
I was unaware of potential issues and put Mobil 1 0W40 in the wifes 55k mile mk1 and my 62k miles mk2. Both appear to be running absolutely fine and the mk1 in particular seems much smoother…
My understanding is that engines that have been running for a long time on mineral oil should not be switched to synthetics as synthetics can dislodge heavy deposits which greatly reduce the effectiveness of the oil.
I also understand that you can “prepare” an engine for synthetic oils by flushing it out first, but in older engines, this can cause the seals to degrade (usually protected by deposits left behind by mineral oil).
This is just what I have read, not through personal experience. I’m very glad to hear that your Mk1 is running better because of it… but my Mk1 has done nearly twice the number of miles.
Why pay P+P charges on a 5L can of oil from MX-5 Parts? 5W30 should be readily available. Try the parts department of your local Ford, Vauxhall or VW main dealer for example, or even Halfrauds if you are desperate.
For what it’s worth:- Put 0W - 40 fully synth into my MK1 with 125k miles on clock. It had only had semi synth in before. No problems, just elimination of HLA clatter.
Hmm, I don’t think I’m going to risk it. Very glad to hear you haven’t had any problems though. I don’t get any HLA clatter at the moment, and the car has been using 10W-40 semi-synthetic for years so I think I am going to stick to that.
Halfrauds do 5 litres of the Mobil stuff for around the same price as 4 litres of the same thing from MX5 parts… and you won’t be paying postage either of course. Just thought I’d mention it.
10/40 is what the engine was designed to run on. I personally think that there is no advantage using fully synthetic oil and would advise to stick with a good quality semi synthetic 10/40.
My car went to a local garage (not main dealer) to have a new clutch fitted so i asked him to do oil and filter change while there, he rang mazda dealer who recommended 5w30.
within a couple of days started leaking oil like a goodun and then started smoking on startup…[8o|]
Now in process of stripping head to replace valve stem oil seals…[8o|]
Was later told because of mileage (120k) should of used 10w 40 as thinner oil has basically flushed engine and cleared all deposits that were stopping leaks. Car probably been run on 20w 50 before i bought it and the change to 5w 30 did it no good.
After rebuild will be using 10w 40 semi synthetic.[Y]
Hmmm. I always thought that it was the detergents in the additives that flushed out all the gum and solids. As such I wouldn’t have thought that a 5W30 oil would have any more detergent than a 10W40 oil. Engine oil for diesel engines has a different additive pack to engine oil for petrol engines, it has a more aggressive detergent to remove and keep the soot in suspension.
I suspect that the oil is too thin for your engine when hot (the “30” aspect of the grade). Maybe a refill with 10W40 or even 5W40 would have done the trick on its own (5W40 would be better if you have HLA clatter on startup)? Failing this, a can of Wynns Engine Oil Stop Leak might have been sufficient to rejuvenate your oil seals.
Are you taking the head off to replace the valve stem oil seals or are you doing the “coil of rope down the spark plug hole” trick? Might be worthwhile stripping down the HLAs and giving them a good clean while you are at it.
Interesting. I have some Motorcraft 5W30 left over from when I had the Focus and Mondeo Zetecs. I was planning on using it in a Mazda but I will drop it at the local recycling centre instead.
There is a very informative thread on HLA cleaning here.
I can thoroughly recommend Greased Lightning Carburettor Cleaner for removing gum and varnish. I’m fairly insensitive to a lot of chemicals but this is evil stuff and will make your hands sting.
Just to add to my previous post, My car is a one owner 30K car regularly serviced at a Mazda dealer. Every service reciept says it recieved Castrol Magnetec 10w-40 so that`s what it shall continue to recieve [Y]
My 1.8 mk2 with 130000+ miles on clock has always been run on castrol magnatec 10w40 and has seemed fine. However noticed in my original mazda hand book recently that they reccomend 5w30 for it and halfords guides say the same for post 99 cars and 10w40 for pre 99 cars anyone know the reason for the change? I was tempted to start using 5w30 in mine due to this info and also my wifes duratec engined fiesta uses it so it would make things simpler. I was also of the understanding that thinner oils offer more protection in general or will they just pee out of my high milage engine?
Really sorry to hear you’ve had problems. This is exactly what I am afraid of - was the oil used previously semi-synth or synth, and the 5W-30 mineral oil? My Haynes manual recommended that you use 5W-30 mineral, but obviously this is from a different era… I agree with Phil that a good quality semi-synth 10W-40 is best for older engines, especially if the engine has a lot of miles on it.
I would like to change to fully synth just to see if it makes any difference, but I cannot ignore the reams of service history that show the car as always having 10W-40 semi synth - I’m not going to risk it.
