What kind of gas used?

[Neonspinnazz]

What kind of gas do you use?

When I get mine I will stick to the specs and go premium!

[John_H]

I've been paranoid about using premium ever since I resolved the problem with my perfrformance raodster: the BMW Z4. I went in to the dealership to have them deal with the hesitation I got when the engine was cold: at my first busy intersection of my drive I hit the gas to burst into traffic to find hesitation!

The dealership told me that premium gas in the Pacific Northwest does not meet BMW combustibility standards and I should use a lower grade of gas. Confused and doubtful, I went back to "plus" grade and found the hesitation went away.

I don't like finding myself in a situation where my car's letting me down so I haven't gone premium here in the northwest. If I move to another part of the country, I'll go premium.

[louis bolieu]

9500 miles on 08 passion and the next drop of premium will be its first (even the dealer pumped regular). avg 45 mpg, smooth running engine. I based my decision on previous cars I owned:
1. '88 5.0 Mustang, driven 145,000 miles, 26 mpg @ 80 mph hwy, still running strong when sold
2. '95 Camaro Z28, driven 137,000 miles, 26 mpg@ 80 mph hwy, still running strong when sold
Both these cars were prescribed to use only premium, never got a drop.

[BigWarpGuy]

At first I used regular unleaded. The last two fillups were premium. I seemed to have higher mpg with the regular than the premium. I will continue using premium to see if the mpg goes up or stays the same. The last couple of fillups were at Shell. Perhaps it is adjusting to the premium?

[theguywiththelongestname]

I use Chevron Supreme 91 (with Techron), the smartmobile runs great.

[JD10367]

I know this argument comes up only, oh, every six hours here, but...

If the car manufacturer tells you to use 91 octane (or 90 octane, but that's another argument for another thread), why would you use 87 or 89?

Do you think they said, "Hey, let's tell our customers to use higher octane, because we want to give people a reason not to buy our car, and we want to see them pay more for gas"?

Numerous threads here have summed up the facts, which are supposedly that: a) if you use a higher octane it's okay (albeit a waste of your money) because the car's computer will adjust for it, but b) if you use a lower octane you will probably decrease your mileage, and who knows what you're doing to the engine which was not designed for it.

Your lower-octane gas is detonating too easily and too early. It will reduce your power and strain your engine parts.

If you drive a car for 15,000 miles a year, and the car averages 30 MPG, that's 500 gallons of gas yearly. The difference between 87 and 91 used to be around .20, but now it's usually around .25 or .30 even. Assuming a .30 difference, for 500 gallons you're paying about $150 a year more for premium (and that's assuming you drive 15k miles, and only get 30MPG). And that doesn't take into account the lost MPG you might be incurring by using 87.

You pay around $15-20k for a smart with options. Is it really worth $150 a year to use cheap gas? That's three dinners out. Or 7 or 8 DVDs. Or a night out at your local casino. Big deal.

I walked into my local kitchen store just now and blew $40 on stuff I really didn't need. Then I went to a gourmet supermarket and blew another $40. That was about six months' worth of "buying premium vs. buying regular", and I didn't even bat an eye. Why is it that seeing those extra dimes on the pump's price sign makes so many people go insane, LOL?

[jediknight36]

There was a link or a picture posted just a few days ago that showed the ethanol uses across the country. Anyone know where that is?

[Westfield 11]

I would suspect that there is a greater difference between cheap generic gas and brand-name fuels regardless of the octane rating than between regular and premium. I get better economy using Chevron and Shell premium than I do using the cheap premium at Circle K and Valero. I am going to experiment with Chevron regular and see if there is any change in mileage from their premium.

[Pops900]

Originally Posted by John_H

I've been paranoid about using premium ever since I resolved the problem with my perfrformance raodster: the BMW Z4. I went in to the dealership to have them deal with the hesitation I got when the engine was cold: at my first busy intersection of my drive I hit the gas to burst into traffic to find hesitation!

The dealership told me that premium gas in the Pacific Northwest does not meet BMW combustibility standards and I should use a lower grade of gas. Confused and doubtful, I went back to "plus" grade and found the hesitation went away.

I don't like finding myself in a situation where my car's letting me down so I haven't gone premium here in the northwest. If I move to another part of the country, I'll go premium.

It's not because the premium gas is no good. It is likely because your BMW engine is designed to run on regular grade gas (87~). Most stock engines are set up for the lower octane. Smart has a high compression to help compensate for the small size so it is recommended to burn high octane.
[CORRECTION: John has given me a quick education that this BMW engine requires 91 octane and the premium gas in that area is no good. See his post on next page. Thanks John]
Octane content helps create the length of fuel burn. 93 octane burns longer in the cylinder than 87 thus creating a bit more time of explosion force for higher compression or longer stroke engines. 87 octane creates more of a 'pop' type of burn to quickly force the piston down. Nowadays computer chips control the fuel burn / air mix and will be programmed matching the octane requirement. These systems can adjust for small differences in fuel content (mix differences within the brand, different brands, different qualities), air flow (clean vs. dirty air filters), oxygen content (low vs. high altitude) , etc. Depending on the program, they will only adjust so far, so it is possible they will not handle the differences covering the span of all octanes.
A few Smart owners report feeling no differernce, while most say they notice something whether in physical performance or mpg. I can't explain why other than differences in location and / or driving habits.
I am also a firm believer that big name brand fuels are better overall than generic.
Disclaimer:
I work in the industry but not in gasoline refining so these comments are by my general knowledge and not expertise. Maybe someone that works in a refinery could expand on this.
Thanks for your time and let's be careful out there,
Pops & Car-lito (eventually)

[kitttie]

So far all of my gas purchases have been at Costco, using Premium. The guidelines are for Premium, I will only pump Premium. I would never put Regular in a car that calls for Premium. I have done 10 fill-ups so far with an average of 37.7 mpg with a mixture of both city and highway driving. I am perfectly happy with the results.