Regular gas in premium gas car

I leased a car and realized few weeks ago that it needed premium fuel. My wife was using regular fuel for months and then we switched to premium.
I understand we made a mistake a very dumb mistake and should have followed it properly from the start. Do you think changing to premium was a good choice now even after we drove the car in regular fuel for some 8-9 months. Can I get into trouble for not using premium Fuel.

Was is required or recommended?

Most modern engine’s have knocking sensors which identify engine cylinder knocking issues which usually are the most common issues related to using wrong octane fuel.

So i would not worry too much.


In theory not using the correct octane could cause engine knock, but most cars that “require” premium fuel have knock sensors in their engines that slow the timing to accommodate for lower octane fuel. As a result you may lose a slight amount of power when using a lower octane fuel (which you will regain once you start using premium again).

But nowadays using the wrong fuel does not permanently damage engines so you’re almost definitely fine. I would personally use premium fuel if that’s what your car recommends, but you haven’t caused any engine damage.

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Not to hijack but supplement OP… what’s the point putting premium in lease, if it does not cause

  • noticeable damage
  • wear n tear or
  • noticeable performance improvement?

Performance. Car and driver did an article with dyno and drag runs, as well as multiple cars.


Ive used only premium in my Bmw, believe me makes a difference in performance! Plus if you lease a car that requires premium, you know at the end, if you do a lease buy out, you’ve done the engine good.

87 won’t cause any damage, but it makes turbos, supers, and high compression engines :unamused::confused::expressionless:

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Our Volvo I4s certainly benefit from premium. No doubt in my mind.

Depends on required or recommended.

If recommended is purely for performance.

If required, there could be number of reasons why it’s required & you just don’t want to be dealing with issues.

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What Car you leased ?
Once I leased a 2017Lexus RX350 and it says Regular Gas on it and one of its selling point as per sales person. I used Regular for a week or so and see it start missing if try to push the gas pedal hard or pickup not good. I took in to get it check . They ran all tests and found nothing. Then the Tech told me to use Premium instead of Regular . Once on Premium issue was gone. As per Tech Premium always gives you better performance but Regular won’t hurt your engine and still good to drive. In my state difference between Regular and Premium is ~ 0.65 cents.

On some engines that ask for premium, you will also get better MPG (and performance) if you are running it. So the savings of using regular may be canceled out. While there is no harm in any modern engine to use 87, you might as well go with what the manufacturer recommends.

Question is if I am leasing a car and sure will return at the end of lease should I care for engine or performance or save $15 on each fillup.

You’re call, but I also think there is a safety consideration: sometimes evasive maneuvers require hitting hard on the pedal to clear/pass something, and you want that pedal to respond and behave properly. Even a moments (milliseconds) hesitation makes a world of difference.

Agree. I always use Premium + in my cars either they are leased or I own them. I can’t stand that hesitation once I pushed the Gas and on freeway you get better mileage too . But on Rental I am sure they put regular once you pick the car and you put regular when returning the car.

Might as well enjoy the full engine performance you’re paying for. The difference is not that substantial over the course of most lease mileage allowances. And if it really matters to save money, you probably shouldn’t be leasing a car that takes premium in the first place!

Between lease, insurance., upkeep, washes most cars requiring premium will cost close to 10k annually driving 12k miles a year.

Trying to save a few hundred bucks seems pennywise/pound foolish.

But it’s your money!

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Says ‘recommended’. So it’s not as bad as I thought.

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Which car is it?

It’s YMMV from my experience

Lexus and Infiniti’s with Toyota and Nissan sibling engines. Have never seen much of a difference

German cars - Premium is usually required and the way to go whenever possible

Because a manufacturer can deny your warranty claim if you put regular gas in when premium is required. Now you are stuck footing a bill that will cost more than the $15 per fill up savings.

From BMW’s warranty for those wondering:

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