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I'm a sucker for pain at the pump.
(lemmy.nz)
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this post was submitted on 13 Jul 2026
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Is it worth it?
I get a bump in mpg and power when using premium so I pay up.
It's required to prevent detonation (fuel igniting in the cylinder before its supposed to due to pressure) which will damage your engine.
Maybe some cars can adjust their tune based on the octane level, but for those that can't it's definitely worth it.
mine specifically says not to use anything but 87. and also to stay away from ethanol-free fuels. so, yes, they can and do tune the engines for a specific fuel mixture.
My turbo K4 specifically says to use nothing but 87. I thought, how odd. Nope, they tuned the Smartstream 1.6T to run very conservatively stock to use 87, any other fuel is wasted.
It doesn't have another map for a higher octane, unlike Mazda which has some sort of black magic to push timing until it micro-knocks and then pulls back timing. Kinda cool.
Shame on Hyundai / Kia. JB4 time soon!
A knock sensor, if equipped, can help adjust timing. My car says premium recommended while my wife's says required. What sucks for us is premium has gone up faster than regular. It used to be about $.60-.80/gallon more, but anymore, it's $1-1.20 extra, making it not very worth the few mpgs and HP gains I get. My wife's turbo car and tune requires it. '_(ツ)_/'
Isn't it more about long term engine health than any immediate mpg gains?
No. Octane isn’t better or worse for your engine. It’s about compatibility.
Octane rating is just a measure of how fast petrol burns. Most gasoline is hexane, 6 carbons, octane is 8 carbons, burns slower. But modern fuel doesn't actually add octane, they use ethanol to slow the burn rate.
No idea why it costs more or is called "premium", it does not cost more to make, nor does it produce more energy.
I avoid cars that require expensive petrol.
With a sticker like that, probably. I have a car that requires premium or else it can ping (predetonate) with the right conditions and risk "ring land" damage. My other car says "91+ recommended". It gets better fuel economy on premium, but the cost of premium is higher than the mpg benefit, even before post-covid premium price gouging that never let up.
What kind of car?
My old Murano*could benefit from premium. But I’d get maybe 1 more mpg and maybe 5-10 more torques. Butt dyno couldn’t even notice it.
Horrified at the thought of a butt dyno
Ford Bronco with the 2.7 and a ford performance ecu flash.
Right? My previous car was designed to be flexible premium cost roughly the same with mpg boost and the car was more powerful. It's really not that different I was a poor college kid at the time too.
Now if your car is premium only and you are putting regular in you are just looking to break something.
My understanding was the premium was just more stable, reducing predetonation with higher compression. Unless you are losing mpg or power to predetonation wouldn't switching make no difference? I ask out of curiosity, I'll admit I know very little on fuel specifics.
Cars with electronicaly adjustable timing will detect if there is knock caused by pre-detonation/pre-ignition and advance or retard the timing to compensate. So cars that can do both octanes will have the timing more advanced when premium gas is present allowing for more power and efficiency. More timing with lower octane gas will explode earlier than expected causing pre-detonation/pre-ignition.
Engines that have premium requirements usually have higher compression, forced induction (turbo super, charger, ect) or even a more aggressive cam setup that advances timing where variable timing can't compensate or it doesn't have variable timing. So they need higher octane in order to ensure the engine isn't igniting at the wrong time, which over time damages pistons, rings and other components.
Also if your car is not designed for both, you are just throwing money away getting premium if it requires regular. Best case no difference or in the case of my wife's car would actually cause a check engine light.
VVT isn't really needed for that though, advancing spark can be enough to avoid knock. Although I'm not sure if an engine like that would receive benefits from premium.
Yes I may be confusing the two here I'll adjust
VVT does achieve the goal too, if you close the valves later you'll def. have a reduced compression ratio. That helps avoid premature ignition through compression. (Well, duh..)
But igniting the mixture earlier also helps, probably won't work for engines that are to high in compression.
And forced induction engines with electronic boost control could lower boost pressure, that would also help avoid knock.
At least that's my understanding...
Ahhh got it, that makes sense. thanks!
Premium often has a better additive package.
I used to regularly swap between the two, and swap computers when I did so, so I'd regularly be burning a mix or the rest of the premium on the stock tune, no difference to mpg. (Untuned)
Depends a lot on the engine or even just the timing.
My 2023 can ramp up and down power by analysing various signals.
I had an old sports car that could detect knock and pull timing but that was about it. Waiting until it knocks isn’t super healthy.
I have an old truck that I could set timing using high octane and get some better efficiency out of it, but I’d rather it be able to run on a mix of sewer runoff and coyote piss so it’s timing is pretty forgiving.
My wife's car specifically says to use regular when available. That made our wallets happy, but I'm considering putting in premium to see what happens.
It doesn’t help. Higher octane resists combustion more. You must tune the engine for it for there to be any advantage.