So I just realized the type of gas does matter

[Ronstang]

I once did a test on this very subject with my 93 Taurus SHO. It is supposed to run premium but will run perfectly fine on regular as the computer simply used feedback from the knock sensors to adjust the timing curve when you run regular.

Not only is there an increase in performance when running premium there is also an increase in gas mileage. When I did this test I calculated my gas mileage with several tanks of regular and then with several tanks of premium. The increase in gas mileage meant that it only cost about 5 cents more per gallon to run the premium, which is less than a dollar a tankful for better performance.

Now every car is going to be different but I would bet the results would be similar and thus there really is not reason not to run the premium fuel.

 

[Throckmorton]

it's also about the ethanol content. 87 will probably have a higher percentage of ethanol than 91/93

I've heard that but I don't really get it. Ethanol itself has higher octane than gasoline.

BTW I've also heard that higher octane tends to have more detergents, so you can benefit from using it every once a while as a cleaner.

 

[BurnItDwn]

Compression doesn't change, ignition timing does. Normally the spark happens some time before the piston reaches the top of its stroke. If you put in lower octane than you need, the ECU makes the spark happen even sooner to preempt detonation. That wastes energy because the piston is fighting the burning fuel for longer

Thanks for the correct info.

 

[Fenixgoon]

This is why I'll never buy a used lux performance car.

Duuhurrrhurrrr i'll pay 50k for a 335i but fuck if I spend the extra buck per tank to put premium in it.

Its more common than you would think.

i will never understand this.

lets suppose you do the average of 15,000 mi/year @ 20mpg. thats 750 gallons of gas. the differential between regular and premium is usually $0.40 in my area. So, $300 difference over the course of a year between regular and premium. If you're buying a car, you should damn well be able to afford that.

 

[lupi]

my first time driving cross country while in the midwest i didn't realize that their "low grade" was actually a couple octane less than the normal regular I was used to. when I went for the next stop I noticed the difference on the pumps after wondering why the car had started to feel odd while driving.

 

[futuristicmonkey]

it's also about the ethanol content. 87 will probably have a higher percentage of ethanol than 91/93

Bingo. Whomever says there is no benefit to running premium in a car for which 87 is recommended hasn't looked closely at any pump lately. Around here, regular and mid-grade both state that they may contain up to 5/10% ethanol whereas premium is 100% gasoline. Gasoline has more energy per unit mass than ethanol.

 

[zerocool84]

They dont even sell 93 in my area. Goes from 87-89-91. I put in Costco gas anyways so its either 87 or 91.

Yep here in Cali there's only like 5 places in the whole state you can get 93.

 

[HarryLui]

I used to throw in a tank of premium every once in a while because it has detergents for injector cleaning and such

That's just wrong. Octane rating has to do with detergents, despite what stickers at the gas station says.

http://en.wikipedia.org/wiki/Octane_rating

 

[Throckmorton]

Anyone have a link to proof that 93 octane has less ethanol? And why would that be when the ethanol is used as an octane booster?

 

[Tristicus]

So does putting in higher gas in a car that requires only regular do nothing?

 

[sdifox]

So does putting in higher gas in a car that requires only regular do nothing?

It empties your pocket faster.

 

[MJinZ]

So does putting in higher gas in a car that requires only regular do nothing?

No... did you read this thread?

It may give you a slight horsepower boost (2-5 perhaps) and fuel economy boost, but cost wise may be less mileage/dollar spent.

 

[Throckmorton]

So does putting in higher gas in a car that requires only regular do nothing?

Read your manual. If it only mentions 87 octane, use 87 octane.

If it says it requires 87 but 91 or 93 is "recommended", use the higher octane.

 

[Tristicus]

Read your manual. If it only mentions 87 octane, use 87 octane.

If it says it requires 87 but 91 or 93 is "recommended", use the higher octane.

I'm not putting anything in my car higher than the cheapest. I'm asking if it makes a difference, IE, engine runs better/worse or the same.

 

[IcePickFreak]

Read your manual. If it only mentions 87 octane, use 87 octane.

If it says it requires 87 but 91 or 93 is "recommended", use the higher octane.

This.

 

[MagnusTheBrewer]

My Mitsubishi Eclipse says it needs premium only and my dad had always put in 91 for the past 10 years using this car. So I was short money the past 2 weeks and had to put in 87. At first I was thinking that it shouldnt be that much diff. Well in accelerating the car felt sluggish and it was working harder. So today I put in 91, to see if it was the fuel or just in my head. Now its feeling speedy like it used to before and I am barely even tapping the gas.

We're talking 20 cents a gallon x (~ 15 gallons) = $3.00
So, you were so tight that one gallon would have stranded you?

 

[Bignate603]

Where are people getting the idea that high octane pump gas has less ethanol? Every place that I've lived that uses ethanol in the gas requires it by law during parts of the year to fight smog. You don't get out of that by buying more expensive gas.

 

[sdifox]

Where are people getting the idea that high octane pump gas has less ethanol? Every place that I've lived that uses ethanol in the gas requires it by law during parts of the year to fight smog. You don't get out of that by buying more expensive gas.

Shell stations up here have a sticker that tells you % of ethanol that could be in your gas. V-Power (the premium 91 octane Shell gas) is listed as ethanol free, but it also mentions where available.

 

[Bignate603]

Shell stations up here have a sticker that tells you % of ethanol that could be in your gas. V-Power (the premium 91 octane Shell gas) is listed as ethanol free, but it also mentions where available.

I live in the Phoenix area and every place is required to use ethanol in their gas during the smog heavy parts of the year, no exceptions.

 

[coxmaster]

I live in the Phoenix area and every place is required to use ethanol in their gas during the smog heavy parts of the year, no exceptions.

It varies by state/city. Most places (that ive seen) have 10% in all grades

 

[SparkyJJO]

So does putting in higher gas in a car that requires only regular do nothing?

It can actually have a negative impact. My car calls for 87. I put 89 in it when the station was out of 87, and while it seemed to run ok it did seem a little less peppy and the gas mileage suffered a little. Higher octane gas resists burning more, so it makes sense.

 

[angry hampster]

OP: Is the Eclipse a turbo model?



Also, I'm so happy to be able to buy regular gas again. Having to use premium in my VW sucked.

 

[exdeath]

One of my pet peeves with cars overseas making more power than the US version, in places with 100+ octane pump fuel nationwide. RON/MON aside, most places in the world get much better fuel than we do in the states, yet they just love to slap us with more regulations and emissions rules to further dilute our gasoline.

 

[exdeath]

OP: Is the Eclipse a turbo model?



Also, I'm so happy to be able to buy regular gas again. Having to use premium in my VW sucked.

Is an extra $2 a fill up for a $40 tank really a deal breaker?

 

[Throckmorton]

I'm not putting anything in my car higher than the cheapest. I'm asking if it makes a difference, IE, engine runs better/worse or the same.

Yes, the engine runs worse and there is more wear on the engine if you use a lower octane than "required" or "recommended".