Now, this guide assumes that you have a pretty standard MX5, not one that runs on rocket fuel. Turbo'd and supercharged cars will need better quality stuff to run nicely. A normal engine will need the usual grade of stuff, one running at twice it's designed horsepower will need the good stuff!

Regular treatment of an engine will make it last much longer- same as anything mechanical.

Just for the sense of background, and to help you understand your engine, here's a rough guide to the four stroke engine. It won't make you a mechanic, but it does help to understand what's going on under the bonnet!

Air goes in your air intake, and goes into the cylinder. The cylinder is the bit where the piston goes up and down, using little explosions of petrol. The moving piston spins the crankshaft, which gets the power from the engine and transfers it to the wheels.

The four stroke engine does all this in four stages, made up of four “strokes” of the piston as it goes up and down.

1 st stroke (intake) – the piston drops in the cylinder, creating a space. As it does this, the air is drawn into your engine. At the same time, petrol is injected into the same space, mixing with the air.

2 nd stroke (compression) – the piston moves back up in the cylinder, making the space smaller, and “compressing” the fuel and air. Compression is pretty important. The better the compression, the more power out of the engine.

3 rd stroke (ignition) – the sparkplug fires. Funnily enough, when the sparkplug fires in a mixture of air and petrol which has been squished down as small as it can go, the result is an explosion. Yay! We have ignition, Heuston! The explosion pushes the piston back down with a fair bit of force. This is where all the power comes from in the engine.

4 th stroke (exhaust) – The piston moves back up the cylinder again, pushing out all the smoke & fumes left over after the explosion. This stuff comes out of your exhaust.

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FUEL

Petrol- the MX5, running at factory specification (i.e. timing set at 10 degrees BTDC) can run on just about any petrol available across the world. It saves Mazda from having to set up the engines differently. Makes sense really. However, in Ireland, we have pretty good petrol. 95 octane, in fact. Not quite race fuel, but close enough! Therefore, many people set their timing to 14 degrees BTDC. The bigger the timing number, the earlier the sparkplug fire in the sequence, giving better compression, as the fuel is fired as the piston is still compressing the mixture. Set it too high, and the cylinder will fire too early (called “pinking”, from the “pink” sound it makes, allegedly), and the explosion will actually reduce engine power, as it will slow the crankshaft down. Not good! Some engines will take even higher timing, but with Irish petrol, the best for performance and fuel economy is 14 degrees BTDC. Oh, BTDC stands for “Before Top Dead Centre”, and means the point where the piston is at the very top of a “stroke”

Fancy Petrol – “Super” unleaded is basically just purer petrol with less of the “bits” left in it. This is used to have less build up of bits left over in your engine. Nice stuff if you've more money than wit. No need for it at all at all! Give your engine a fill of it once every now and then, though, and it'll help keep the insides of your engine clean.

“High-tech” petrol – V-power, Pura and the like all have different additives & stuff in it to do different things, like clean the engine, give more power or whatever. They might have some effect, but not that you'd really notice. If it really did what it claimed to do, we'd all be using it all of the time. It's nice, but it ain't magic.

Diesel – Don't put this in your engine, unless you have a fetish for mechanics.

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OIL

There are lots of different types of oil for different things. For your main engine oil, there are three main types-

1. Fully synthetic oil
2. Semi-synthetic oil
3. Mineral oil (sometimes called “Dino” oil, as it's basically rotted dinosaurs, i.e. it's organic!)

Most engine oils out there are mineral oil. It's cheap. Just dig a really deep hole in the ground at the exact right spot, and there it is! Most engines are designed to run on the stuff, except really high performance ones. The MX5 can survive rightly on the stuff. Fine if you don't want to pamper your baby!

Synthetic oils are artificially made to do exactly what it says on the tin. They are much more slippery, and makes your engine work a whole lot better by removing more friction from the moving parts (like them piston things which keep going up and down!)

Semi-synthetic oils are a mixture of the two above. Price is about halfway between the two other types.

Mineral or Dino oils are a real mixture of stuff, so aren't quite as good as synthetic at removing friction. Synthetic oils are better for your engine, but usually cost a whole lot more than the ordinary stuff. You will save money in the long run, however, as things last a lot longer when using decent oil! There have been reports of some synthetic oils causing problems, but not in our experience. My advice is to use the best oil you can afford.

There are different grade of oils, generally describing the “weight” of the oil. The heavier the oil, the higher the numbers will be. Oils are used in other areas of the car to keep things moving smoothly, such as the gearbox and differential (fancy part of the axle)

For the MX5, the following “weights” of oils are specified for the different uses:

Engine oil – 10W30 (for synthetics, 5W30 is fine) 3.6 litres needed

Gearbox – 80W90 or 75W80 2.0 litres needed (manual gearbox)

Dextron II or M-III for automatics, 4.0 litres needed

Differential oil – SAE 90, about 1 litre needed

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PLUGS

Spark plugs – Tired of saying “they're for an MX5” over and over again to the guy in the motor parts shop? Here's the spark plug numbers you're looking for!

Manual transmission-

NGK sparkplugs BKR6E-11 (alternatives are BKR5E-11 or BKR7E-11)

Nippon Denso sparkplugs K20PR-U11 (alternatives are K16PR-U11 or K22PR-U11)

Automatic transmission-

Nippon Denso K20PR-U11

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