I fill up with Sunoco 94 octane. What I notice though, is that there's a distinctive smell coming from the exhaust. Don't know how to describe it--it's gassy smell? Or maybe sulfuric? I hope some of you know what I'm referring to, I don't have the adequate word for it. Anyway: should I continue with a gas that smells like this? Does it mean the gas is leaving deposits in my fuel system? I thought the higher the octane, the more "clean-burning" and deposit-free it's supposed to be. Someone enlighten me? I faintly recall in the owner's manual some mention of gasoline that smells funny, forgot if there was a recommendation about it.

From your Owner's Manual:Your vehicle was certified to California’s low emission
vehicle (LEV) standards as indicated on the
underhood tune-up label. It is designed to optimize
engine and emission performance with gasoline that
meets the clean burning low-sulfur California gasoline
specifications. If you live in any other state than
California, your vehicle will operate on gasoline
meeting Federal specifications. Gasoline sold outside
California is permitted to have higher sulfur levels,
which may affect the performance of your vehicle’s
catalytic converter and may produce a sulfur
exhaust odor or smell. SUBARU recommends that
you try a different brand of unleaded gasoline having
lower sulfur to determine if the problem is fuel
related before returning your vehicle to an authorized
dealer for service.

It's a common smell associated with most gasolines higher than 93 octane. That smell is even more pronounced in the higher octane race gasolines.

Yeah.. Some high octane gas smells so sweet...Like Cotton Candy...Go to a drag race and hang out at the staging lanes...Your'e bound to smell it...along with burnt rubber...

Zee:cool:

Sulfur is definitely in fuel, and depending on what part of the country and what type of fuel it comes in varying amounts. Do a little research on BMW e34 v8 motors, they had to extend the engine warranty to 100,000 miles due to the high sulfur concentration in US gasoline eating away at the cylinder walls and killing compression. And I will tell you this much, that 4 ltr v8 really sucked with compression leaks :(

We don't have to worry about the engine though, it was eating at a nickel additive in the engine block.

Originally posted by paulnose
We don't have to worry about the engine though, it was eating at a nickel additive in the engine block. [/B]

Paul are you referring to the Subaru engine here? So Subaru engines should be able to take high sulfur concentrated gas? Any recommendations for a lower sulfur-content gas? Is Sunoco the only gas brand in New England area that makes octane higher than 93? I'm from CA, so I don't really know about the gas brands here.

I wouldn't recommend using gases really high in sulfur on any engine, but the subie engine should be fine, the problem was really with the bmw engine alloy for that model. As far as fuels over 93, Sunoco's 94 is the only one that I know of. For sulfur content Dated EPA results (http://www.epa.gov/orcdizux/regs/ld-hwy/tier-2/colucci.pdf) They may have more recent results, just look around the EPA's site. California does have the lowest sulfur content fuel however due to requirements, and premium has a lower content than regular. Sulfur is bad for the emission control system regardless of the car. I'd basically stick to major brands, like mobil, exxon, sunoco, shell, texaco. I never use Getty, Citgo, or any of the others in this area, but that may just be personal preference, but search on the boards and you'll hear of a turbo horror story with some mom and pop getty gas.

Hey Paul thanks for the info! Yeah, my first gas-up here was at a Citgo, didn't know better.

When you said the premium gas has lower sulfur content than regular, were you speaking about all gases across the States in general, or only specifically about CA premium and regular?

If it's true for all states, Sunoco 94 should contain less sulfur then Sunoco 93 or any of the other 93 brands?

It's acrosss the states in general except california. You probably won't see much of a difference between the 93 and 94 though. Also to do a little testing I put mobil 93 in my tank today, as opposed to my usual mobil 87, for the first few miles it lagged a little in low-mid second gear accelleration. Then it was fine. Also when really reving the engine into the 6k+ range I smelled some sulfur, which was odd cause hardly ever smelled it with the 87, only a few times up really steep grades under full accelleration. This was flat out. So may just be the car adjsuting, I'll see on my driving later tonight how it adjusts. Also the california sulfur levels are <30ppm whereas premium elsewhere only need to be below 350ppm or something ridiculous like that. As for the octane rating, it's only a rating of the fuel's resistance to knocking nothing more. It just so happens that an octane booster such as MTBE that is added to many gasolines also has oxygenating properties that clean up emmissions as well.

The State of Maine seems to conduct ongoing sampling of incoming gasoline for sulfur and MTBE levels. Here's a link for 2000 data: http://www.state.me.us/dep/air/mobile/fuelspage.htm .

The sulfur levels seem lower for 93 octane compared with 87. But there's amazing variation even within a particular octane from a particular terminal. So it seems to me easily possible that the sulfur level at any given gas station pump will vary substantially over time.

350ppm?? dang that's why I noticed the difference. There's actually some campaigning against using MTBE, because that's supposed to be harmful to the environment. So at some of the Unocal 76s in CA, they have MTBE-free stations.

If sulfur is bad for the emissions system, should I do some maintenance for it (e.g. cleaning it?) over the years? Does sulfur affect car performance or car reliability? This is different from fuel deposits in the fuel system right? I believe most gasolines have some kind of detergent additives nowadays to help reduce deposit buildup.

MTBE is on some phase out in CA, The EPA is constantly doing studies and finding various results on the impact of MTBE's in the ground water. Check the EPA site, there should be lots of informatino on the Groundwater contamination with MTBE, but the effects are still somewhat up in the air. Interesting though, it doesn't have as high a BTU rating, but burns more of the gas due to it's oxygenating qualities, you should find out how much MTBE is in each grade of fuel. I know mobil in my area has MTBE in all grades, so the high octane is probably just loaded with MTBE, Maybe so much so that it reisists knock more as the octane rating suggest, but performance increase may not be there due to the lower BTU rating.