You’re standing at the pump, shivering a little because the wind chill is no joke today, staring at those three yellow buttons. Regular. Plus. Premium. The price gap between them feels like a personal insult some mornings. You might be wondering, is unleaded plus the same as premium, or are you just paying for a middle-ground placebo? Honestly, most people just mash the 87-octane button and go about their lives, but if your car manual "recommends" something higher, the confusion sets in.
It’s not just a marketing gimmick. But it’s also not the "super-fuel" people think it is.
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Let’s get the big answer out of the way immediately: No. They aren't the same. Unleaded plus is essentially the compromise candidate of the fuel world. It usually sits at an 89-octane rating, while premium typically hits 91 or 93. If you put plus in a car that explicitly requires premium, you aren't giving it the same thing. You're giving it a "close enough" that might actually cause issues depending on how modern your engine's computer is.
The Chemistry of Why They Aren't Identical
Octane isn't about power. It’s about stability.
Inside your engine, pistons are flying up and down. They compress a mix of air and fuel. If that fuel is too "unstable," it explodes too early from the heat of compression alone, before the spark plug even fires. That’s called pre-ignition. You’ve probably heard it referred to as "engine knock." It sounds like a metallic rattling or pinging. It's bad. Really bad. Over time, knocking can literally punch holes in your pistons or shatter spark plugs.
Premium fuel is designed to be harder to ignite. That sounds counterintuitive, right? You’d think better gas would burn faster. Nope. It’s formulated to resist pressure so it only burns when the spark plug says so.
Unleaded plus, being the middle child, has more of those stable hydrocarbons than regular, but fewer than premium. In most U.S. states, gas stations don't even have a dedicated tank for 89 octane. They literally have a blender pump that pulls 60% or 70% from the regular tank and mixes it with 30% or 40% from the premium tank right as it flows into your car. It’s a cocktail.
When "Plus" Is Just Throwing Money Away
If your car's manual says "87 Octane Recommended," then buying plus or premium is basically like giving a tip to a multi-billion dollar oil company. They don't need your charity. Your engine isn't designed to take advantage of the higher stability. It won't run cleaner. It won't go faster. It definitely won't get better gas mileage.
The Federal Trade Commission (FTC) has actually been pretty vocal about this for years. They've noted that for most vehicles, higher octane provides absolutely no benefit. Yet, people still fall for the "Plus" button because the word sounds better than "Regular."
Marketing works. "Regular" sounds cheap and basic. "Plus" sounds like you care about your car. "Premium" sounds like a luxury. But your engine doesn't have feelings; it has compression ratios. If the compression isn't high enough to require 89 or 91, the extra additives are just being blown out the exhaust.
The High-Performance Headache
Now, let’s talk about the people who should care.
If you drive something with a turbocharger—think a Volkswagen GTI, a BMW, or even some of the newer Ford EcoBoost engines—the stakes change. These engines use turbos to cram more air into the cylinders. More air means more pressure. More pressure means you need that stability we talked about.
If the manual says Premium Required, do not think is unleaded plus the same as premium because your engine sensor will know the difference. Modern cars have "knock sensors." If you put 89 in a car built for 93, the sensor detects that tiny pinging you can't even hear yet. The car’s brain (the ECU) then retards the ignition timing to protect the engine.
The result? You lose horsepower. Your gas mileage actually drops. So, by trying to save $4.00 at the pump by choosing plus over premium, you might end up spending $6.00 more in lost efficiency over the course of the tank. It’s a losing game.
Real World Examples: The 89 Octane Mystery
Who is 89 octane actually for?
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There are a few specific engines, mostly older Chrysler/Stellantis HEMI V8s (like in the older Ram 1500 or Jeep Grand Cherokee), where the engineers specifically "mid-grade" was recommended. They found that 87 caused a tiny bit of pull-back in timing, but 91 was overkill.
Then you have altitude. In Denver, gas is often sold as 85, 87, and 89. Why? Because the air is thinner. Less air in the cylinder means less pressure, so you can get away with lower octane. In the mountains, that 89 "Plus" actually acts a lot like 91 "Premium" does at sea level. Physics is weird like that.
Breaking Down the Additives
Some people swear by premium because of "detergents." Brands like Shell or Chevron talk about their "V-Power" or "Techron" blends. While it’s true that some premium fuels have a slightly higher concentration of cleaning agents, the law requires all gas to have a minimum level of detergents.
Furthermore, many brands now meet the "Top Tier" detergent standard across all grades. This means the 87 you buy at a Top Tier station has the same high-quality cleaning gunk as the 93. Check for the Top Tier logo on the pump. If you see it, the "plus" isn't giving you a cleaner engine than the regular.
Making the Final Call at the Pump
Still unsure? Look at your gas cap.
If it says "Premium Recommended," you can use plus or regular in a pinch, but the car won't be happy. It'll survive, but it'll be sluggish. If it says "Premium Required," you are playing Russian Roulette with your engine's internals by going lower.
The "Plus" button is the most ignored button in the industry for a reason. It’s rarely the "right" choice. It’s usually either too much for a basic car or not enough for a fast one.
Actionable Steps for Your Next Fill-Up
- Check the manual once. Don't guess. If it says 87, stop looking at the other buttons. You're wasting money.
- Listen for the "marbles." If you accelerate uphill and hear something that sounds like marbles rattling in a tin can, your octane is too low. Move up one grade next time.
- Avoid the "plus" trap. If your car requires premium (91+), don't settle for 89 thinking it's "close enough." It isn't. The engine will still pull timing and kill your performance.
- Trust the Top Tier. Instead of buying higher octane for "cleaning," just make sure you’re buying from a station that meets Top Tier standards. It’s better for your fuel injectors than a random "plus" grade at a shady station.
- Ignore the "Super" hype. Unless you've modified your car with a custom tune or a massive turbo, 93 octane won't make your Toyota Corolla a race car. It just won't.
Stick to what the engineers who built the engine told you to use. They spent thousands of hours in a lab testing these tolerances so you don't have to guess at the pump. If the manual says 87, buy 87. If it says 91, buy 91. The 89 in the middle is a ghost that only a very specific group of car owners actually needs.