Cheap Vs. Expensive Oil Change: Should You Spend Less Or More?

If there's one aspect of automotive culture known to almost anyone, it's expense. Car payments, maintenance costs, auto loans, and so on all contribute to one of the largest money sinks in the average household. Consequently, it's only natural for us to want to cut costs as much as possible. If your car doesn't need overly expensive fuel, high-performance perishables like specialized brake pads and fluids and such, then why bother? I myself am guilty of this, having serviced all my own cars since I was first able to drive. I've owned numerous classic cars in various stages of working order, ranging from barely roadworthy to a 15-year and counting daily-driver. But one thing common to all these cars, as well as every car I've serviced while working as a mechanic, is that they all need oil.

When you go into an auto parts store to purchase oil, you're greeted with a literal wall full of different brands, weights, and price points. After understanding the fundamentals of motor oil and selecting which weight is correct for your car, next comes the question of how much you're willing to pay. Is there even a difference between the cheapest and most expensive oil? Do some cars prefer a cheap oil change versus an expensive one, by extension?

The short answer is that what's most important is following the oil change interval. Lower-quality conventional, otherwise-known as mineral oil, is less durable; the base formula it uses is inherently less long-lived than synthetic and so needs to be changed more often, sometimes as quickly as every 1,000 miles depending on your driving habits. Will it harm your engine to run cheap oil? Likely not — most cars today will run either perfectly fine. But let's dive into the specifics and discuss it in-depth.

First and foremost, even cheap new oil is likely going to be preferable over old, well-worn expensive oil. However, putting cheap oil in your engine will drastically decrease your oil change interval by as much as half or more. Typically, depending on what car you own and what the manual says, you should expect anywhere between 5,000-10,000 miles for a typical oil change. But with the cheapest oil you can find, this number drops down significantly because the oil breaks down faster than more expensive synthetic counterparts. It's one of the hallmark determining factors when selecting mineral versus synthetic motor oil. And while some mechanics recommend mineral oil for specialist applications such as classic cars and Wankel engines, the general rule-of-thumb is that you get what you pay for.

All this relates to what actually comprises cheap oil. Mineral oil is essentially just crude oil pulled from the ground, refined several times to remove impurities, and bottled as-is. It contains several basic compounds, mainly natural hydrocarbons, and various additives to help improve its performance. Contrary to the popular belief that conventional is just straight-up oil, mineral oils still feature these additives. Like synthetic, they enhance the oil's anti-wear and anti-oxidation properties. The only major difference between a synthetic and conventional is the base used to create it. The actual processes used to extract and refine conventional oil remain cheaper than formulating synthetic, hence the price gap. But that also makes the oil less-optimized for certain applications.

There are numerous factors influencing why synthetic oil works better than conventional, the most obvious being that it's designed that way. Much like how humans cultivated certain plants for millennia, we can't reasonably do that with mineral oil, but we can with synthetic. Because the oil is developed under lab conditions, it'll always yield more optimized results than a naturally occurring equivalent. Of course, this only applies to the base formula; much like mineral oil, synthetic also features various detergents, anti-oxidants, and anti-friction agents, composing about 10-20 percent of the oil formula.

The main reason why this oil performs so well is its chemical stability. Synthetic oil features highly stable and uniform molecular bonds, which perform well under a wider temperature variation than conventional oil. This means that synthetics feature a narrower viscosity index; they hold their consistency better through differing temperatures. And, more pertinent here, synthetic oil lasts far longer than conventional. If I were to put six quarts of synthetic in my classic Jeep with several hundred thousand miles, I'd expect an oil change interval of about 5,000 miles with a good filter, as opposed to half that with conventional.

Over the long term, this actually saves me money because it means that my engine has less deleterious problems like sludge buildup, and I pay about the same for fewer changes as I would for many conventional changes. Can I attribute my engine's longevity to the quality of oil I use? Not directly. But it certainly doesn't harm my engine either, and if it's about preserving the life of the engine in as cost-effective a manner as possible, I'll always favor the more expensive option in my own cars, and it's what I'd recommend if you're changing your own oil.