Engine Oil Buying Guide

Engine oil helps to keep your vehicle running smooth. This engine oil buying guide will help you understand the basics of what’s happening under the hood.

Engine Oil 101

Engine oil lubricates the motor, but it also does much more. It’s a master multi-tasker that keeps things purring under the hood. Engine oil keeps your engine greased so parts don’t wear down from friction; it traps and suspends debris and fuel fumes, which prevents them from reaching the motor; it removes heat from the combustion chamber, which keeps the engine cool; it prevents corrosion and rust forming from oxidation on the engine. Engine oil is a key part in your vehicle’s performance, so it’s important to pay attention to what goes into the tank under the hood.

Engine Oil Basics


Oil changes

An oil change is one of the most important maintenance tasks you can do to reduce repair costs. If you take your car to a mechanic or service technician for an oil change, they usually take a few minutes to check and service different parts of your vehicle, like:
  • Lubricate the suspension and steering, and check for obvious wear or damage
  • Check the underside of your vehicle for leaks or other obvious issues
  • Check the oil levels in the differential and manual transmission
  • Check all under-the-hood fluid levels
  • Check belts and hoses
  • Check the air filter
The rule of thumb is to change your oil every three months, or every 3,000 to 5,000 kilometres. Create a reminder for yourself — either on your phone or on your calendar — so you don’t forget or let too much time go by.
Each Tire & Lube Express oil change includes a 15-point vehicle inspection. Among other things, Walmart auto technicians check your battery performance, wiper blades, tire tread depth, brakes and headlights.

How to check your oil levels

It’s important to know how to check your oil levels. Understanding your oil levels will help to protect your engine from damage from low oil levels or infrequent oil changes. It’s easy to do, and only takes a few minutes:
  1. Before you start, make sure the engine is cool and the car is on a level surface to ensure accurate readings.\
  2. Take the dipstick out of the oil tank and wipe away excess oil with a clean, lint-free cloth.
  3. Insert the dipstick into the oil tank, take it out again, and read the level.
  4. The difference between the maximum and minimum levels is at least half a litre.
If you’re running low on oil:
  1. Check your owner’s manual or ask someone in store for what oil grade your car needs.
  2. Take the oil cap off and slowly pour in a little new oil.
  3. Wait a few minutes. Check the dipstick, and add more oil if needed.
Remember to pour the oil slowly and check your dipstick often to avoid spills from overfilling.

Oil grades explained

5W-50. 15W-40. 10W-30.
Confused by the jumble of numbers and letters on a bottle of oil? You’re not alone. The combination of numbers and letters indicates how well the oil will flow at certain temperatures — in freezing winter conditions, or sweltering summer heat. In low temperatures, the oil needs to remain fluid, but at higher temperatures, it’s important for the oil to stay thick enough for the moving engine parts to stay lubricated. Today, most oil types are multi-grade, meaning they’re a combination of oils that perform at different temperatures
The first number (5-10-15-20-25) refers to the viscosity grade — or the oil’s resistance to flow — at low temperatures. Cooler temperatures call for thinner oils to make sure the oil flows and everything under the hood stays lubricated. Quite simply, the lower the grade, the thinner the oil. If you’re driving through the winter, it’s important to look for oil with the letter “W” after the first number. This type of oil meets standards for cold-weather conditions.
The last number (30-35-40-45-50-55-60) refers to the oil viscosity grade at high temperatures. When the heat is on, oil will thin out, so under these conditions thicker oil has more staying power between contact surfaces than thinner oil. The higher that last grade number is, the thicker the oil will be. Good to know: older cars will need a higher grade in hot temperatures to minimize friction.
Remember to check your owner’s manual to find out what oil grade — or viscosity — is right for your car.

Oil types

There are three main types of oil: conventional, synthetic and synthetic blend.
Conventional oil, also known as crude oil, is natural oil that’s been refined to be used in cars. It’s extremely sensitive to temperature changes and prone to imperfections. Conventional oil is generally more affordable than synthetic oil, but you’ll have to change it more often.
Synthetic oil is made from man-made compounds other than those found in conventional oil, and also consists of more uniform molecules. Synthetic oils are more slippery and tend to perform better at a range of temperatures, making them a popular choice.
Synthetic blend oil is — of course — a blend of conventional and synthetic oil, making it a happy medium between performance and price range.

Oil additives

Oil is 70-85% base oil, but anywhere from 15-25% of the oil is made of additives. These extras help your oil to keep your engine running smooth.
  • Anti-foam additives prevent air bubbles from forming in the oil, which creates foam. This foam can make the oil harder to pump through the engine, reduce its ability to cool the engine and prevent it from lubricating properly.
  • Anti-wear additives prevent metal-to-metal contact in your engine by coating surfaces with a protective residue.
  • Antioxidants prevent sludge, deposits and thickening in the oil, and can also extend your oil’s lifespan
  • Detergents keep high-temperature parts clean, which prevents them from developing deposits.
  • Dispersants keep sludge from forming on the engine by dispersing contaminants and suspending them in the oil.
  • Friction modifiers reduce friction in moving engine parts, which helps your car run efficiently.
  • Pour-point depressants are used in multi-grade oils to make sure the oil flows well in cooler temperatures.
  • Rust and corrosion inhibitors coat metal parts to prevent rust and corrosion.
  • Viscosity index improvers are polymer additives that help keep the oil flowing over a range of temperatures.

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Expert tips

If you’re changing or filling up your oil tank, there are a few important tips you should know:
  1. The wrong oil grade can cause engine damage, so always top up with the right grade of oil for your car.
  2. Low oil levels can damage your engine, so check your oil gauge and dipstick regularly.
  3. Don’t overfill your oil tank. Pour your oil in slowly and check your dipstick often to make sure right amount of oil is added
  4. Keep an extra container of oil in your car in case you need to top up
  5. Replace your oil filter with every oil change
  6. Change your oil every three months, or every 3,000 to 5,000 km
This article is intended as general information. Always be sure to read and follow the label(s)/instruction(s) that accompany your product(s). Walmart will not be responsible for any injury or damage caused by this activity.



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