Could regular fuel be better then premium?

[FinalShift]

According to a friend of mine, he has read somewhere that it is better to use regular fuel in some cars. His reasoning is that Premium fuel can hurt the engine because some of those cars he does mention are not intended to be run on premium therefore the ending might be damaged. Also the same vehicles get better MPG on regular then premium. Is there any Truth to this?

[Clegko]

It all depends on the car. If you have, say, a Toyota Yaris, it will run better on Regular Fuel (87 Octane here) than it will on 93 Octane (Premium). However, if you have a Ferrari or some other high performance vehicle, the higher the octane rating, the better. Up to a point, anyway. Jet Fuel would be overkill.

[M_Bolc]

Your friend is right, except that running premium gas won't damage an engine. The main difference is the octane rating, the higher octane rating a fuel has, the more resistance it has towards combustion.
Premium (higher octane) fuels should be used in high compression engines or such, if you use a high octane fuel in a not so high performance engine, not all the fuel will be consumed, resulting in slightly reduced power, more polution, and less fuel economy.
On the other hand, running low octane fuel in an engine that requires a higher octane rating will cause predetonation (better known as knock), that will lead to damage if used for a long time.

[grease]

The octane rating of gasoline is representative of how much compression a given gasoline can take before it self detonates. Higher compression engines need higher octane fuel so that the gasoline doesnt explode before the spark plug ignites it.

It doesnt really matter if you run higher octane fuel in a lower compression engine. You're just wasting money. It may relieve some knocking at higher rpms but you're never going to reach those with daily driving and most high revving engines are high compression anyway and require a higher octane.

And as far as increased fuel mileage goes: the above poster is correct in that it may actually reduce mpg (although a very minute amount).

[NecroJoe]

Basically, if the owner's manual of the car recommends a certain fuel, that's the fuel it's designed to work best with. If your car requires premium fuel, then there is a chance for something more severe than simple a couple less horsepower or lower mileage. However, if it onle "recommends" premium fuel, than your engine can work fine with all of them, you just sacrifice a few horsepower (usually no more than 5-10) and a couple mpg's.

If your engine isn't designed to exploit the higher-octane fuels, it shouldn't be much (if any) worse, you'd simply be throwing money down the toilet.

It would be like putting 1 small heirloom tomato in a big pot of tomato sauce with a bunch of regular tomatoes. Unless the receipe is built to showcase the "fancier" tomato, you'd never know it was there, and are just wasting your money. However, if you're making a nice caprese salad and the recipe can support the extra complexities the heirloom tomato can offer, well then the upgrade would be worth it.

[grease]

Originally Posted by NecroJoe

It would be like putting 1 small heirloom tomato in a big pot of tomato sauce with a bunch of regular tomatoes. Unless the receipe is built to showcase the "fancier" tomato, you'd never know it was there, and are just wasting your money. However, if you're making a nice caprese salad and the recipe can support the extra complexities the heirloom tomato can offer, well then the upgrade would be worth it.

You're making me hungry.

[vette5885]

I'm happy to see so many accurate posts. I find that most people have the assumption of "oh, 91 is higher than 87, so it must be better" or "91 is more expensive than 87, so it must be better", which is unfortunate.

As it's been said, run what the car calls for.

[NecroJoe]

Originally Posted by vette5885

"oh, 91 is higher than 87, so it must be better" or "91 is more expensive than 87, so it must be better"

Oh, and don't forget...it's "Premium" and that must mean it's the best! I'll bet "Regular" has sticks in it, and I'll bet "Mid" is just spicy water.

[MadCat360]

I remember something about old Honda race bikes. They were putting 91 in them and they would run fine until high RPM when the fuel couldn't burn fast enough. They switched to 87 and everything was cool...

[NooDle]

^yeah what they said.
on a related note, don't get the "V Power" extra super performance fuel though. It does nothing except cost more monies.

[klutch]

Originally Posted by M_Bolc

On the other hand, running low octane fuel in an engine that requires a higher octane rating will cause predetonation (better known as knock), that will lead to damage if used for a long time.

If cars didn't have anti-knock sensors, at least. Putting 87 in your Benz won't 'damage' anything, but you won't be getting the performance or milage you paid for.

[SL65]

I use to run my car on Premium when it only required Regular. Simply because I could, and because I thought it would be better. But my car used more fuel on Premium in my usual city driving.

However - if I'm out on the highway/freeway doing long distances and higher speeds, its much better when I use Premium for fuel economy.

But using Premium won't damage your engine.

[Ottobon]

duh! The fuel won't completely combust and you will leave deposits all over your exhaust valves, making you run slowing and look like a smelly fool.

[edkwon]

Originally Posted by SL65

I use to run my car on Premium when it only required Regular. Simply because I could, and because I thought it would be better. But my car used more fuel on Premium in my usual city driving.

However - if I'm out on the highway/freeway doing long distances and higher speeds, its much better when I use Premium for fuel economy.

But using Premium won't damage your engine.

but your NA 2.5 engine isn't exactly some high hp high compression monster, what exactly is 'better' when you run your engine on premium? Because the notion that an engine tuned for regular fuel running on premium generates better performance, is usually placebo effect.

If youre saying your engine runs smoother, that would be odd as well unless there was something wrong w the engine or fuel injection system.

[Clegko]

Originally Posted by edkwon

but your NA 2.5 engine isn't exactly some high hp high compression monster, what exactly is 'better' when you run your engine on premium? Because the notion that an engine tuned for regular fuel running on premium generates better performance, is usually placebo effect.

If youre saying your engine runs smoother, that would be odd as well unless there was something wrong w the engine or fuel injection system.

Actually, i've noticed the similar in my little 2.2 Honda. For city driving, I use el-cheapo 87 octane gas, but if i'm taking a roadtrip (Try to take one at least once a month... love to drive), i'll fill 'er up with Premium. It seems to be more smooth and a bit more peppy up in the higher RPMs, where the engine spends most of it's time when i'm driving at or around 75 (85, 95... same thing. ). Odd, yes, but it's just an odd little quirk that my car has.

[melbournian]

I was reading the Drive lift out in the Age newspaper the weekend before last or something...they filled three identical Corollas with regular, premium and 10% ethanol adn ran a series of blind tests using multiple drivers. The e10 car was cheapest to fill but used a lot more fuel and ended up more expensive, and the regular car used a little bit more fuel than the premium, but not enough to off set the price difference between regular and premium - so the regular ended up being the cheapest to run.

[M_Bolc]

Originally Posted by klutch

If cars didn't have anti-knock sensors, at least. Putting 87 in your Benz won't 'damage' anything, but you won't be getting the performance or milage you paid for.

True, but use regular cheap fuel in a turbo Audi (like I did onece), and in some situations (low revs, high throttle opening usually) they will knock like crazy. There's only so much knock sensors can do...

[Das_Idiot]

yeah it's completely dependent on the car itself. Some will require premium, some will benefit from it but don't require it (like mine) and some just are designed for 87 octane and using higher octane fuel can cause other issues.

Use what it states to use on the inside of your fuel filler door or the owners manual. That's really where this should end.

Also, kudos for the Christmas Clarus and you're from OK too... Huh.

[LeVeL]

Use whatever the owners manual recommends. My car needs premium - people have tried filling up with regular and the engine started knocking badly and there was a noticeable drop in power. A car that's supposed to use 87 should run fine on 93 but why pay more if its fine with 87?

[Cobol74]

Originally Posted by LeVeL

Use whatever the owners manual recommends.

Seriously, do not muck about with it unless the owners manual says you can - for all the reasons stated.