It happens to the best of us. You’re checking your dipstick on a Saturday morning in Lahore, realizing the level is a bit low, but you don’t have a spare bottle of the exact same oil you used during your last service. You head to the nearest shop, but they only have a different brand or a slightly different viscosity.
The question immediately pops up: Can I just pour this in? Will mixing these two oils damage my engine, or is oil just oil?
In the world of automotive maintenance, there are plenty of “garage myths.” Some people claim mixing oils creates a sludge that destroys engines instantly, while others say modern oils are so advanced that it doesn’t matter at all. The truth, as is often the case, lies somewhere in the middle. While your car won’t likely explode the moment you mix two brands, doing so can compromise the very protection you’re paying for.
The Science Behind Engine Oil Compatibility
To understand why mixing is a debated topic, we have to look at what is actually inside that plastic bottle. Engine oil isn’t just a single liquid; it is a sophisticated cocktail of base oils and chemical additives.
Base oils make up about 70% to 80% of the product. These can be mineral-based (refined crude oil), fully synthetic (chemically engineered), or a blend of both. The remaining 20% to 30% consists of additives: detergents to keep the engine clean, dispersants to prevent sludge, anti-wear agents, and viscosity index improvers.
Base Oils and the Mixing Myth
Technically, all motor oils are compatible. Industry standards, such as those set by the American Petroleum Institute (API), require that oils be able to mix with each other without causing physical separation or gelling. If you mix a synthetic oil with a mineral oil, they will stay blended.
However, “compatible” does not mean “optimal.” When you mix a high-performance fully synthetic oil with a cheaper mineral oil, you aren’t getting a “best of both worlds” scenario. Instead, you are diluting the superior properties of the synthetic oil. You’ve essentially paid for premium protection and then weakened it by introducing a lower-grade base.
Why Viscosity Grades Shouldn’t Be Blended
Viscosity is the measure of an oil’s resistance to flow. It’s the “5W-30” or “20W-50” printed on the label. This rating is perhaps the most critical factor for your engine’s health, especially in a climate like Pakistan’s, where temperatures can swing from chilly winter mornings to blistering 45°C summer afternoons.
If your engine is designed for 5W-30 and you top it up with 20W-50, you are changing the flow characteristics of the lubricant. On a cold start, the thicker oil might not reach the upper valvetrain fast enough, causing metal-on-metal contact. Conversely, if you put thin oil into an older engine designed for thicker lubricants, the oil film might be too thin to protect bearings under heavy load.
Mixing different viscosities results in an unpredictable “middle ground” weight. Your engine’s oil pump and internal tolerances are calibrated for a specific thickness. Moving away from that spec—even by mixing—can lead to increased internal friction and higher operating temperatures.
The Hidden Danger: Additive Interference
This is where the real risk lies. Every oil manufacturer, from global giants to local favorites available at the Makki oil Store, uses a proprietary recipe of additives. These chemicals are designed to work together in a delicate balance.
When you mix Brand A with Brand B, you are mixing two different chemical “recipes.” There is a possibility that the additives in one oil might clash with the additives in the other. For example, the anti-wear agents in one brand might compete for space on the metal surfaces with the detergents of another brand.
This doesn’t usually cause a catastrophic failure, but it can significantly reduce the oil’s effectiveness. The oil may break down faster, lose its ability to neutralize acids, or fail to keep carbon deposits in suspension. Over a few thousand kilometers, this “chemical soup” won’t protect your engine nearly as well as a single, consistent product would.
Emergency Top-Ups vs. Regular Servicing
Life doesn’t always go according to plan. If you are on a long route and your oil light comes on, and the only oil available is a different brand or grade, pour it in. Running an engine with a mix of two different oils is infinitely better than running an engine with no oil at all. An emergency top-up to reach the “Full” mark on your dipstick is a temporary fix that won’t cause immediate harm. However, once you are back in a city like Lahore with access to proper facilities, it is a good idea to perform a full oil change sooner rather than later to restore the correct chemical balance.
What you should strictly avoid is making mixing a habit. Some drivers try to save money by mixing leftover bottles of different brands. This is a false economy. The money you save by using up old bottles is tiny compared to the potential cost of premature engine wear or a clogged catalytic converter.
Protecting Your Engine in Pakistan’s Harsh Climate
In Lahore, our cars face unique challenges. We deal with extreme heat, heavy stop-and-go traffic, and significant levels of dust and environmental pollution. These conditions put immense stress on engine oil, causing it to oxidize and shear much faster than in milder climates.
Because the environment is so demanding, the quality of your oil becomes your first line of defense. Before worrying about mixing brands, you must ensure that the engine oil is original or fake, as the market is often flooded with recycled or low-quality lubricants that can’t handle our local heat.
When you use a consistent, high-quality product, you allow the additive package to do its job properly. Consistent use of the same brand and grade builds a protective layer on engine internals that isn’t disrupted by competing chemicals.
Final Verdict: Is it a Costly Mistake?
Is it safe? Yes, in an emergency.
Is it a mistake? Generally, yes, if done during routine maintenance.
Mixing engine oils is like mixing two different types of high-end paint; they will blend, but the color and finish might not be what you expected. To maintain the longevity of your vehicle, stick to one brand and one viscosity grade for every oil change interval. If you must mix in an emergency, make sure the replacement oil meets the same API or ACEA specifications required by your vehicle manufacturer.
By being disciplined with your maintenance and sourcing your lubricants from a trusted partner like the Makki oil Store, you ensure that your engine stays clean, cool, and protected for years to come.
FAQs
1. Can I mix synthetic oil with normal mineral oil?
Yes, they are physically compatible and will mix. This is essentially what a “synthetic blend” is. However, adding mineral oil to a synthetic oil reduces the performance and longevity of the synthetic product.
2. Will mixing oil brands void my car warranty?
Generally, no, as long as the oils used meet the minimum performance standards (like API SN or SP) and viscosity grades required by your owner’s manual. However, it is always better to keep receipts of a single, consistent oil type.
3. What happens if I mix 5W-30 and 10W-40?
You will end up with a viscosity somewhere in between the two. The oil may be too thick for cold starts compared to a 5W-30, or too thin for high-heat protection compared to a 10W-40. It is best to avoid this unless it is an emergency.
4. If I switch brands, do I need an engine flush?
In most cases, no. When you drain your oil, a small amount (about 5-10%) remains in the engine. This tiny amount won’t cause issues when you fill up with a new brand. A flush is only necessary if the engine has a history of severe neglect or sludge buildup.
5. How do I know which oil is right for my car in Lahore?
Always refer to your owner’s manual first. For the local climate, many modern cars do well with 5W-30 or 10W-40, but the specific “API” rating is just as important as the viscosity.
6. Can I mix oil from two different manufacturers if the viscosity is the same?
Yes, but it’s still not ideal. Even if both are 5W-30, they use different additive packages that may not work as effectively together as they would individually.
