MicksGarage Blog
  • Menu 
    Filter Home
    Project GTI
    DIY Guides
    Most Popular
    Motorsport
    Driving
    Travel
    Car Safety
    General News
    How Stuff Works
    Car Reviews
    MicksGarage.com
    About us
    Contact us
    Work with us
  • Store
  • Subscribe
  • Close Menu
  • Filter Home
  • Project GTI
  • DIY Guides
  • Most Popular
  • Motorsport
  • Driving
  • Travel
  • Car Safety
  • General News
  • How Stuff Works
  • Car Reviews
  • MicksGarage.com
  • About us
  • Contact us
  • Work with us
  • Store
  • Subscribe
  • Car Parts
  • Car Accessories
  • Batteries
  • Wiper Blades
  • Gifts & Toys
  • Oil
Understanding Engine Oil

Understanding Engine Oil

So you want to top up your car's engine oil and you want to do it yourself - maybe you've seen our DIY videos! You know where the dipstick is, you know the procedure and all you need now is some oil. But you're wondering, which engine oil for my car?

What engine oil do I need?

Oil is oil, right? But when you go to buy the stuff, there’s a huge range of options available at all kinds of prices. When you pick up a bottle or look more closely at the specifications you’ll be met with a seemingly random series of letters and numbers and, what's worse, they're similar to those on another identically priced bottle, but different enough to make you wonder if there's something else you should know! Fear not, we’re here to talk you through what it all means, in a (mostly) jargon-free manner. We've let the boffins get in on this though as they're the only ones that truly understand it all...

Just Tell Me What Engine Oil For My Car!

If you’re not really interested in what all the jargon means but just want to make sure you get the right motor oil for your car you can use our car engine oil finder - simply enter your reg and away you go - we'll show you a full list of the exact oil that will suit your car. 

Which oil suits my car

The Basics of Car Engine Oil

There are three core types of engine oil on the market: mineral, semi-synthetic and synthetic.

  • Mineral oil is the cheapest and is essentially a constituent of crude oil, produced after it is refined. Few car companies recommend this these days as it generally doesn't come with the engine-cleaning detergents that are required these days and has a limited temperature operation range. Saying all that, it's perfectly fine for older engines whose tolerances are less extreme and that are used in a mild climate without freezing or really hot weather.
  • Synthetic oil or Fully Synthetic oil is the most expensive, but for a reason. It has been engineered by scientists to work over a wide range of temperatures and conditions, while reducing drag on the engine to help reduce fuel consumption. It also actively cleans the engine's internals as it’s pumped around.
  • Semi-synthetic oil is a blend of mineral and synthetic oil to help bring the price down.

Understanding Engine Oil Viscosity

The large numbers on a bottle like 5W30 engine oil or 10w40 engine oil refer to its viscosity. It's loosely defined as the 'flowability' of the oil. Put another way, thin oil has low viscosity, while thick car oil has high viscosity. So for example, beer has low viscosity and golden syrup has high viscosity. Just don't put those in your engine...! Ambient temperature, i.e how hot or cold it is outside also has an effect on the engine oil in your car. When it’s cold, the oil will flow more slowly, when it’s hot, the oil will flow more quickly. However, In order to lubricate an engine properly the oil must be able to flow at a consistent rate through a broad range of temperatures. To put this in perspective, imagine a jar of Golden Syrup, put it in the fridge (at roughly 1-3 degrees C) for a few hours, then take off the lid and try to pour the syrup out. It will start to flow but understanding engine oil viscocityextremely slowly as the cold temperature has made it more viscous. Now take your jar of syrup and stick it in the oven for 20 minutes at 100 degrees C then take the lid off and pour it out. It should flow out extremely easily. The heat has reduced the viscosity and allowed the syrup to flow more quickly. The same thing happens with engine oil. If you live in Siberia and it’s -20 degrees outside, when you go to start your car’s engine, the oil inside it needs to be thin enough to flow and lubricate all the internal components as soon as you turn the key. Similarly, if you live in Dubai and it’s 50 degrees outside and you’re driving in heavy traffic your engine oil needs to stay viscous enough to lubricate properly. At the moment there is no one oil that can cope with all these situations and for that reason, the SAE (Society of Automotive Engineers) introduced a grading system which tells us how suitable a grade of oil is for a certain temperature range. So…oils are manufactured to different viscosities in order to be effective in different climates and operating conditions. To broaden the range of temperatures that oils can be used in, grades of oil are combined. These are known as Multi-grade oils

Understanding the Numbers:

Most oils these days are Multi-grade (multi viscosity) and will have two numbers on the label separated by a ‘W’ (e.g. 5W-30) There are oils with a single viscosity rating (e.g. SAE 20W) known as Mono-grade oils but they are less common these days. The SAE tests oils and assigns an arbitrary weight or grade (viscosity) number to the oil depending on its flow rate at different temperatures. The SAE numbering systems goes: 0, 5, 10, 20, 30, 40, 50, 60. The grade refers to the oils ability to flow or lubricate an engine at a certain temperature. The lower numbers are thinner, less viscous oils suitable for low temperatures generally found in winter. The ‘W’ seen in an oil’s grade stands for ‘winter’ (eg 5W30)

  • 0W oil will flow correctly up to -30 degrees C
  • 5W oil will flow correctly up to -25 degrees C
  • 10W oil will flow correctly up to -20 degrees C
  • 15W oil will flow correctly up to -15 degrees C
  • 20W oil will flow correctly up to -10 degrees C.

The flow rate of oils are also tested at a ‘hot’ temperature of 100 degrees C to simulate a running engine. The 2nd number in a Multi-grade oil refers to the ‘hot’ viscosity of the oil. So a 5w 30 engine oil at 100°C will only thin as much as its higher rating. Think of it like this: a 5W30 oil is a 5-weight oil that will not thin more than a 30-weight oil when it gets hot. Multi-grade oil ratings look like this: SAE 5W-30. This is based on a 5W oil, tested at -25 degrees C, but at high temperature, it will not thin out more than a '30' weight oil would. SAE simply stands for the Society of Automotive Engineers, the organisation responsible for defining a numerical system for grading car oils. There are alternatives, such as ACEA (European Automobile Manufacturer's Association) and the API (American Petroleum Institute), but SAE is generally considered the standard in this part of the world.

Low SAPS

  • If you have a modern turbodiesel car that has a diesel particulate filter (DPF) in the exhaust then you must use low SAPS oil.
  • SAPS stands for 'Sulphated Ash, Phosphorous, Sulphur' and it's often referred to as simply low ash oil.
  • In Europe, according to the ACEA, low ash oil is labelled as C1 (0.5% ash), C2 (0.8% ash - better suited to higher performance engines) and C3. In America there's CJ-4.
  • So an engine oil labelled 5W30 C1, C2 or C3 is a 5w30 grade oil suitable for cars fitted with DPF’s. If your car has a DPF be sure to check if C1, C2 or C3 specification oil is required.

Carmakers' own oil grades

  • Just to confuse everyone, many car makers have their own grades of oil that must be used in specific models. These almost always have an equivalent in the SAE grading system so can be cross-referenced.
  • Specific Volkswagen Group cars (Volkswagen, Audi, SEAT and Skoda) are supposed to run grades that are marked 'VW 500.00' to 'VW 508.00'.
  • BMW gives its approval to oils with its 'BMW Longlife' rating, or LL rating indicating that they're suitable for long service intervals on specific models. Example: BMW LL04
  • Mercedes-Benz approved oils are marked 'MB-Approval' followed by a number that refers to a paragraph and page of the 'Mercedes Bluebook' used by dealers.
  • Renault, Peugeot, Citroen, Porsche and others also use their own codes
  • .castrol oil

Top tips

  • Don't automatically assume that the most expensive oil is the best option for your engine. Always stick to the oil grade and specification recommended by the car manufacturer, as the engine would have been developed using that.
  • Though it's tempting to go for the oil grade with the widest rating, it's best to choose one with the narrowest range that still suits the ambient temperatures you're likely to experience, as it will be better optimised over that range.
  • If you decide to swap from an inferior oil to using synthetic oil it's advised that you change the oil and filter soon after, as it's possible that carbon deposits and other detritus could be cleaned out by the new oil.
  • Using synthetic oil does not mean you can extend the amount of time between engine oil change. The detergents and other chemicals deteriorate over time and reduce the oil's effectiveness.
  • Always change your oil filter at the same time as your oil, as it catches unwanted material before it's circulated to the rest of the engine.
  • Never, ever, drive your car with the engine oil light illuminated. It means that the oil pressure is low, which could lead to catastrophic engine failure in a very short amount of time.
  • Get into the habit of checking the oil level of your engine regularly - once a month for newer cars used infrequently, or even weekly for older cars and those used for high mileage.Understanding Engine Oil oil-infographic

Explore Car Engine Oil By Grade

  • 0w8 engine oil

  • 0w16 engine oil
  • 0w20 engine oil
  • 0w30 engine oil
  • 0w40 engine oil
  • 0w50 engine oil
  • 5w20 engine oil
  • 5w30 engine oil
  • 5w40 engine oil
  • 5w60 engine oil
  • 10w40 engine oil
  • 10w50 engine oil
  • 10w60 engine oil
  • 15w40 engine oil
  • 20w50 engine oil

Explore Engine Oil by Brand

  • Castrol engine oil
  • Total engine oil
  • Valvoline engine oil
  • Mobil engine oil
  • Shell engine oil

 

Read more technical articles  

Category: About Us

Author: The Filter Blog Team

17 December 2023
  • Wind Deflectors 2025
SALE
Engine Oils, Castrol GTX 5W30 A5/B5 Full Synthetic Engine Oil   5 Litre, Castrol
Castrol GTX 5W30 A5/B5 Full Syntheti...
€49.99 €51.49
SALE
Engine Oils, TOTAL Quartz 9000 Future NFC 5W30 Engine Oil   5 Litre, Total
TOTAL Quartz 9000 Future NFC 5W30 En...
€52.99 €59.00
SALE
Engine Oils, Wolf Essential SN C2/C3 5W30 Full Synthetic Engine Oil   5 Litre, WOLF
Wolf Essential SN C2/C3 5W30 Full Sy...
€36.99 €39.00
Engine Oils, TOTAL Quartz INEO LONG LIFE 5W30 Engine Oil   5 Litre , Total
TOTAL Quartz INEO LONG LIFE 5W30 Eng...
€60.99 €72.41
SALE
Engine Oils, Castrol GTX 10W40 A3/B4 Semi Synthetic Engine Oil   4 Litre, Castrol
Castrol GTX 10W40 A3/B4 Semi Synthet...
€34.10 €42.54
Engine Oils, TOTAL Quartz 9000 5W40 Engine Oil   5 Litre, Total
TOTAL Quartz 9000 5W40 Engine Oil - ...
€57.99 €64.99
SALE
Oil and Fluid Extractors, 12V Oil Extractor Pump, AMIO
12V Oil Extractor Pump
€29.99 €34.99
Oil Drain Pans and Funnels, Portable Oil Drainer 6 Litres, Lampa
Portable Oil Drainer 6 Litres
€21.99

Latest Offers!

Dash, Rubber and Plastics, Gummi Pflege Rubber Protection for Door Seals and Windows, Nextzett
Gummi Pflege Rubber Protection for D...
€7.99 €11.41
Bike Racks, Peruzzo Venezia Silver Rear Door Mounted Bike Rack for 3 Bikes, Peruzzo
Peruzzo Venezia Silver Rear Door Mou...
€93.99 €144.60
SALE
Emergency and Breakdown, Holts Tyreweld Emergency Puncture Repair   500ml, Holts
Holts Tyreweld Emergency Puncture Re...
€10.99 €13.29
Interior Organisers, Seat Organiser with Cool Bag, Streetwize
Seat Organiser with Cool Bag
€7.99 €11.00
Sun Shades, Heat Reflective Windscreen Sunshade   150x70cm , AMIO
Heat Reflective Windscreen Sunshade ...
€4.99 €6.24
Bike Racks, Nordrive Bike One Silver Roof Mounted Bike Rack (Frame Holder) for 1 Bike, NORDRIVE
Nordrive Bike One Silver Roof Mounte...
€59.00 €88.99
SALE
Jump Starter, NOCO GB40 Genius Boost Plus   1000A UltraSafe Jump Starter, NOCO
NOCO GB40 Genius Boost Plus - 1000A ...
€137.99 €179.99
SALE
Bike Racks, Thule HangOn Towbar Mounted Bike Rack with Tilt for 4 Bikes, Thule
Thule HangOn Towbar Mounted Bike Rac...
€199.95 €249.99
SALE
Seat Covers, Universal Outdoor Sports Single Seat Cover   Black  Grey, Walser
Universal Outdoor Sports Single Seat...
€10.99 €19.00
SALE
Roof Boxes, Modula Ciao 340L Black Roof Box, Quality at low price, Modula
Modula Ciao 340L Black Roof Box, Qua...
€229.00 €249.99
SALE
Interior Organisers, Standard Folding Shopping Trolley, Streetwize
Standard Folding Shopping Trolley
€18.99 €27.12
Window Tint Film, Window Tint Film   SUPER DARK BLACK 0.75x3m (5%), AMIO
Window Tint Film - SUPER DARK BLACK ...
€14.99 €18.74
Gifts, Car Karaoke System With Bluetooth FM Transmitter, Streetwize
Car Karaoke System With Bluetooth FM...
€31.99 €39.99
Sun Shades, Molly Rear Screen, sunshade, black polyester silk   50x100 cm, Lampa
Molly-Rear Screen, sunshade, black p...
€4.99 €6.24
Kids Travel Accessories, Disney Minnie Mouse Car Sun Shades 44x35cm with Suction Cup   Pack of 2, Disney
Disney Minnie Mouse Car Sun Shades 4...
€4.99 €6.24
Kids Travel Accessories, Marvel Spiderman Car Sun Shades 44x35cm with Suction Cup   Pack of 2, Spiderman
Marvel Spiderman Car Sun Shades 44x3...
€4.99 €6.24
Sun Shades, Molly Contour Sunblock, side screen sun shades   45x65 cm, Lampa
Molly-Contour Sunblock, side screen ...
€5.99 €7.49
Interior Organisers, Backseat organizer with tablet holder, Lampa
Backseat organizer with tablet holde...
€12.32 €15.40

Related posts

Understanding Engine Oil
Everything You Need To Know About Your Car Battery

...

Understanding Engine Oil
The Ultimate Guide To Wing Mirrors

...

Understanding Engine Oil
Dealing With Sun Glare

...

Understanding Engine Oil
Driving On Ice and Keeping Control

...

30 Things You Should Have In Your Boot

MicksGarage Blog

Filter Home
Project GTI
DIY Guides
Most Popular
Motorsport
Driving
Travel
Car Safety
General News
How Stuff Works
Car Reviews
MicksGarage.com
About us
Contact us
Work with us

Travel

Roof Racks and Bars
Roof Boxes
Bike Racks
Tow Bars and Hitches
View all Travel

BBQs
Garden Furniture
Patio Heaters
Games And Activities
View all Summer

Service Parts

Service Parts
Batteries
Wiper Blades
Engine Oil
View all Service Parts

SUP

SUP Boards
Kayaks
Boats
Wetsuits
View all SUP

Car parts

Car Parts
Brake Parts
Lamps & Mirrors
Steering & Suspension Parts
View all Car parts

Tools

Garden Tools
Hand Tools
Power Tools
DIY Service Tools
View all Tools