Look, a petrol car needs petrol and a diesel car needs diesel. These are things we know. If you don’t, it’s written on your fuel cap or on your Registration. Look no further, we’ll tell you how to know what fuel to use.
Then why are there like 3 different kinds of petrol and only 1 kind of diesel? Why are there numbers on petrol? Who knows?
We do and in about 2 minutes you will too.
How Do I Know Whether to Use Petrol or Diesel?
Your fuel cap should tell you which fuel to use. If it doesn’t but it does say “UNLEADED FUEL ONLY” then your car takes petrol.
In the rare case that that fails, check your registration papers, it should say on the slip whether it’s petrol or diesel.
If you’re really struggling, if there’s another card above the registration with a barcode and a km’s indicator then it’s diesel. That’s your diesels “Road User Charges”. If you only have the registration card in the corner of the windscreen and no second slip, then petrol it is.
What’s the difference between Petrol and Diesel?
Petrol is more flammable, lighter, and created in a different way to diesel. Petrol comes in different levels of octane. They both come from crude oil. However there are other ways to obtain diesel, such as biodiesel, which comes from plants.
Diesel has more energy than petrol, which is why you often hear people getting better mileage in diesels. you need less diesel liquid to get the same power as petrol. Diesels also don’t have spark plugs and create combustion from compression.
A lot of that is super complicated, but here’s the main thing:
YOU CANNOT PUT PETROL FUEL IN A DIESEL ENGINE AND YOU CANNOT PUT DIESEL IN A PETROL ENGINE
So what do the numbers on petrol like “91”, “95”, and “98” mean?
Those numbers are the octane rating of the fuel. Basically, the higher the number, the cleaner, and stronger the explosion. Generally, a car with a higher compression ratio, or has forced induction, will require a higher octane. Your manufacturer will generally recommend an octane rating for an engine.
You’re effectively paying for a more efficient and powerful petrol when you buy premium.
For reference, diesel is manufactured to be around 25-40 octane. Which is why you can’t mix the two fuels. Ideally you know what fuel to use now.