That’s my point, should oil changes have anything to do with time? If it takes you ten years to do 12,000 miles, have the protective qualities of your oil actually diminished over time, again, I doubt it.
There’s a lot of people who don’t smoke, I’m one of them. But I’d rather buy a case of Châteauneuf-du-Pape than change my engine oil unnecessarily…
I don’t drink alcohol either 
Bravo!
To say oil should turn black due to cleaning the engine doesnt really cut it for me.
Its like saying i let my neck get filthy so when i wipe it with a cloth it turns the cloth black. ewwww. It is not something most people would do to say they are getting value out of the cloth or wipe
If changing golden oil for new golden oil it just means your engine is not getting dirty.
I would rather not let my engine get dirty. And clean oil will 100% work better at its job than older black oil.
Drag cars get stripped down after minimal running for a reason and its to ensure the parts are not going to fail on the next run.
Changing oil is preventative maintenence just not to the extremes of dragsters which would be ridiculous on a road car or even track car.
And on the drink front ,i do partake and will continue that as well, as again its personal choice . Each to their own i guess.
Think I’ll find an oil forum and follow the science on this one…
I think engines do ‘get dirty’ as a natural product of the way they work. To use your cloth analogy, if you were using that cloth to clean up, say, your dirty stove you would expect it get dirty as otherwise you would not be removing the crud off the stove.
Anyway, clearly folk have different views and will do what works for them, and that’s fine 
njkmr, what’s your thoughts on brake fluid? Manufacturer’s recommenced schedules or do you think it lasts longer? Genuinely interested in this as I’ve requested it at my next MOT, but I’m now questioning whether it’s actually required.
I had some highly desirable cars when I was younger and far less well off than I am now, and although I scrimped on servicing, none of my cars ever failed me. I guess that’s why I’m dubious about service schedules, which I believe are condensed to extract maximum profit from their product.
Anyway, each to their own, and certainly not worth an argument.
That’s sort of true. If it’s clean oil, then it’ll last pretty much forever, however as soon as you start the engine, that changes:
“Products of combution” (water, soot, unburnt fuel, etc.) condense on the cold metalwork of the engine and accumulate in the oil. They tend to be acidic. Water builds up in the oil until the oil has got hot enough to start boiling it out again. This isn’t an instantaneous thing, so the oil needs to be HOT for some time to get rid of the water (which is why running an engine off load for 15 minutes a month to ‘keep it turning over’ is about the worst thing you can do to it).
Other things (like soot, etc.) stay in the oil. When you stop the engine and it cools down, ‘products of combustion’ remaining in the crankcase can condense again - you can’t get rid of the water completely.
Motor oil contains additives that control the acidity (pH) of the contaminants and reduce reactions between them and the metal of the engine. These additives are consumed in the process and so need to be renewed periodically (by changing the oil), hence the “or 12 months” stipulation.
When they become exhausted, the engine typically suffers corrosion on bearing faces where oil is trapped when the engine stops.
Thanks MisterG1, that was an interesting read. Where was that quoted from as I’d quite like to read the article.
That’s certainly more like the science behind it, which is appreciated.
I change my oil every 12,000 miles, so every second year roughly. I’m still not convinced on the 12 month thing, but maybe that’s just me.
Oil is always an ‘interesting’ discussion.
Is brake fluid a similar thing?
Not quoted directly from anywhere - it is standard stuff for tribology.
There’s a huge body of research if you want to find out more - A quick look yielded:
https://www.sae.org/publications/technical-papers/content/04-14-03-0013/preview/
For what it’s worth, I’d probably push the interval to 2 years if I was doing a lot less than 12k miles in that time and I only did longer journeys, but that’s just personal prejudice.
ETA: Not the same as brake fluid - I believe it can be tested for water content and changed (or not) on condition.
Regarding the 12 month thing: Oxygen has a rather inconvenient habit of oxidising things. If I remember rightly, the oil itself oxidises into carbolic acids, which corrodes and stains most things, including metals. Also the detergents break down and aren’t as effective at doing their important job of cleaning up all those nasty stinky bits of stuff. There’s two assumptions I have made for some time as to why the 12 month interval is so prevalent.
I have no problem with changing the oil once a year, but 12K miles on the same oil filter seems stretching it too far. I personally would at least change the oil filter every 6K-7.5K miles or once a year, whichever first and the synthetic oil every 12K miles or once a year, whichever first. So this could mean changing the filter twice per oil change if doing 12K-15K miles per year. I don’t do anywhere near this mileage for my ND.
For brake fluid just buy one of these Car Brake Fluid Test Pen 5 LED Indicator Brake Fluid Tester DOT3 DOT4 DOT5 Brake Fluid Tester Car Diagnostic Tool - AliExpress 34 then you will know the water content and adjust the schedule to your situation.
Sdg111, hi,
brake fluid again gets the golden treatment.
Brake fluid does tend to go much darker brown when its past its best.
But Im not as ■■■■ on changing the brake fluid to be honest. I know its a critical component but ive never had a car or know anyone whos fluid caused disasterous issues.
My mx5 has had several bits of work done on the brakes in my ownership so the fluid has been changed probably twice in 5 years ,only because of changing calipers, master cylinders etc.
I do have an slk which has never had it changed in 9 years of ownership but gets checked by the guy who services it for me every year. It doesnt do much mileage either <1000 miles last year but when hes checked it he tells me its fine. I tend to hang around while he services it. Its kept in a dry garage and doesnt see much rain etc so i go with his advice on brake fluid. Although if common concensous was that old brake fluid led to seized calipers or worse then i would get it changed every 2 yrs like most service guides suggest.
But oil , every year for me, minimum.
Thanks MisterG1,
You kind of put that in a more scientific way for us. Appreciated.
Its really a personal choice i think on what experiences you have had over the years. Who you have talked too about oil and the perception of what is required.
Its certainly not worth arguing over as its never going to be exactly the same for any individual.
You only have to see someone get in a cold car leaving work ,then screeching down the road at full power before the oil has even circulated properly ,let alone warmed up. This pretty much makes our discussion irrelevent as driving style is probably just as important as well as having mechanical sympathy.
Im always ready to learn a bit more on a subject so thanks for the info.
Regards
Rob.
9 year old brake fluid is not good and I would be 99.9% certain that the water content will be very high.
Brake fluid testers are cheap so why not invest.
My old 1993/4 Astra had a dealer service with the filter and oil changed twice every year, but then it was doing 20K+ a year.
When I scrapped it after 205K (only because bits dropped out of the clutch and repair cost more than the car was worth) the engine was still working perfectly, actually better mpg and emission figures etc than new because it was now well run-in!
You are probably right Malc.
I had a look at the link at testers so one will be ordered in the next ten minutes.
What i will also do is report back with the condition of the fluid in both cars once tested.
Regards
Rob.
It’s interesting isn’t it? This is just like other areas of enthusiasts’ use of products and getting maximum longevity out of them. We have a set of clear manufacturer’s recommendations (12,500m/1yr for oil/filter and 2yrs for brake fluid) and we put lots of effort and some cost into trying to improve on it becuase we know it’s not optimised or we believe we know better.
Another example is how far you charge your phone up. 0-100% is supposed to compromise battery longevity. 20-80% is supposed to help a lot. I actually do that(!) and finally we have both IOS and Android offering options to limit charging to 80% for exactly that reason. So to be fair there are occasions where manuacturers change their minds.
And another example of that is my 1.4 Audi, where it’s gone in the opposite direction. Cam belt changes were required every 5 years/50,000m if I recall. This was ONLY in the UK and popular wisdom was it was the UK distributor making money for their dealer network. Last year they aligned with the rest of Europe with MUCH longer recommended change intervals (120,000m or thereabouts).
So one school of thought is “use it as the manufacturer specifies currently, don’t worry, and just enjoy it”. The other is to enjoy the fiddling/tweaking that comes with trying to opimise stuff with tribal and derived knowledge.
At the end of day for most folk it’s probably rust that will ultimately determine our MX-5’s end of life anyway, not oil change interval even if you stick with Mazda’s defaults, especially if you have a modicum of common sense not to thrash it whilst the engine’s still cold, only do short trips etc 
On my Vextra-B , they issued a recall after only 18K from new to change the cam-belt and all its plastic pulleys (possible cracking of them). They also reduced the change interval to 30K from the original 50K.
What eventually killed the car at 20 years old was a cam belt failure, only 12K after a change. However what triggered the failure was not a faulty pulley or bearing, but the spring breaking in the cam belt tensioner. That had also been changed along with all idlers and water pump as part of the service kit!
Again a repair would have cost more than the car was worth.
The Mazda3 replaced it.