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Gas Quality and similiar Myths
Lucky Cynic
Registered User regular
Registered User regular
Okay guys, I have been wondering this for quite some time. I have asked quite a lot of people and have gotten a rainbow of answers. Just what is the difference between Premium gasoline(Higher Octane) and regular? I have heard that regular can cause problems down the road where as premium gas cleans out the tank and other stupid shit. I drive a 2002 Mitsubishi Diamante which has a bigger V6 engine compared to the other cars some of the other guys are driving but I do not have a manual and nowhere in the gas tank cap area does it say "Premium only". I do not push my car to any extremes but it still is a bigger more powerful engine, so would the use of the 92 Octane gas do anything or is it all just a conspiracy to make some more money?
According to these guys, I ought to put in Premium.
http://www.fueleconomy.gov/feg/noframes/17731.shtml
But what do you guys say? I mean, it's been paid off (thanks Dad) and it really is a nice car. I just want to hold onto it for a good while and have made sure to change air filters, oil etc. all that stuff all on time. EDIT: Oh! I should probably note, a good amount of my miles or so are on the highway going 40-60mph.
According to these guys, I ought to put in Premium.
http://www.fueleconomy.gov/feg/noframes/17731.shtml
But what do you guys say? I mean, it's been paid off (thanks Dad) and it really is a nice car. I just want to hold onto it for a good while and have made sure to change air filters, oil etc. all that stuff all on time. EDIT: Oh! I should probably note, a good amount of my miles or so are on the highway going 40-60mph.
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Otherwise it's pretty much useless. Most V6 should take the mid grade and v8's usually premium.
I remember my blazer started idling funny. We took it in and the guy asked if I had been using regular from Wawa. I had, and apperantly it was right after summer and something about differant mixes I dunno. But the guy told me to drop some supreme or whatever in it with some fuel injector cleaner. I floored it down route 1 for about two minuts and it was fine after that.
In general higher octane gas in a "standard" car does nothing but waste money, since the engines were tuned to perform with a particular range of gas.
The only "up side" of some of the higher octane fuels is they "may" have less gunk in them. This is pretty much up for debate on how much would be in any particular brand/grade of gas, and what impact it might have on your cars engine over time.
If you really want higher quality gas, get Chevron. Apparently, the Techron additive really does make a difference as far as keeping your engine clean and such. Shell uses the same additive. Or, at least, this is what my friend's uncle who drives a gas truck tells me.
Yep, a perusal of the manual while waiting for a friend of mine to show up to a movie revealed that, "premium fuels do not enhance performance but increase the cost of operating your vehicle." I drive a Honda. So, just look at your manual; just like oils are designed for particular engines, gasoline is also designed for particular engines.
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I suppose in the long run, whether it's Citgo or Chevron or Bob's Gasmart supplying the gas there's still probably only a few places it was likely to have come from prior to that, though, which may be what you meant by "all the same gas".
This is correct, the base "gas" only comes from a few places. Additives and exact mixes do vary a fair deal however.
The biggest issue is the actual station itself and how legit they are. Most of the big name places won't be a problem, but every now and again you get some owners who are real cheap bastards and literally water down their gas. Now, water (or other similar cheap filler) in the gas in small amounts is not a big deal, as it's impossible to ensure none gets in, but in large amounts it really fucks with your car. I don't hear of this too often anymore, but I have known a few stations where people try and pull this crap. They usually only do it in the low grade gas because that's what they sell the most of.
That's like most anything else dealing with cars. Some places are up front and honest about what they do, others try and bend you over the moment they think they can get away with it.
other way around. engines are designed for particular grades of gas. if your manual says you need it, you need it.
most normally aspirated engines use 87. high performance and forced induction engines use higher grades. using lower grade gas in these engines produces knock, and degrades your performance.
If you drive almost any kind of high-performance car, or most luxury cars nowadays, you most likely need premium. These cars always list this in the manual, and almost always list it on the fuel filler door. (Sometimes in the gauge cluster as well)
If your car doesn't say this anywhere, and you haven't done anything special to it, 99% of the time you are wasting your money.
Yes, this is correct.
Exactly. It all comes down the octane rating, that's it.
And as an aside, if your car is fairly newish, and calls for a higher-octane rating, in many cases you can get away with putting lower octane gas in. The computer will automatically detect the detonation, and retard the timing to compensate. Obviously you'll have a drop in horsepower, but it can be done.
Whether or not it should be done is another story. Long periods of heavy knocking can kill an engine pretty quickly, so if your computer doesn't adjust the timing properly, or it turns out your particular vehicle doesn't have that feature, you're doing damage. Stick with what your manual says, and you won't run into any problems (or alternatively, you'll have someone to blame and sue when something does go wonky).
Read this:
http://en.wikipedia.org/wiki/Octane_rating
and this:
http://en.wikipedia.org/wiki/Engine_knocking
Honestly, read your owners manual and put in what they recommend. I drive a 00 Jeep Wrangler, and 87 (US octane rating) is recommended; I use 89 though, because my engine seems to perform better. If I went to 93, my engine would perform worse (I get a check engine light after a couple of tanks).
And if they recommend the minimum, you can always try one step higher to compare gas mileage - if it goes up (assuming you are driving in the same manner), then stick with it. If it goes down, you can always go back to the previous rating.
This site is wrong: http://www.fueleconomy.gov/
For my vehicle, I regularly get 20+ MPG in a mountainous area (no AC running). I drive about 60 miles a day, and my vehicle has been very well maintained, so maybe that is skewing the results.
Not to have this derailed from the topic or anything; but I think Thinatos meant that the gas you pull out of the pipeline and put into your delivery trucks is all the same. Citgo puts gas into the pipeline at point B and pulls an equal amount of gas out at point A. Once you pull it out you throw in your additives to make it 'your' gas and you are all set to truck it to a station. Much cheaper to ship the gas through pipelines across the US than to have trailers move it all over the place.
Seriously, you guys.
OTOH, I called up the Dealership who said that yeah it does need premium but the guy said he has the exact same car and year and told me that the medium 87 octane fuels works just as well.
Thanks for the links though. Any thoughts on what that dude said, though? He seemed pretty convincing and told me to worry about other maintenance and to "just be sure to change the oil on time."
ok, so do you trust "some dude" (who may or may not actually have the car in question, and may or may not actually fill it with 87), or the engineers that designed your engine?
Well, he was the dude who did show me the car the first time I rolled onto the lot. He did seem to know his car stuff pretty damn well and I will be honest, some of the stuff he was talking about the engine size/etc was going over my head but he knew a lot about this car and not just the salesman shpeel. The second time I did, I got some other guy and bought it then like a few weeks later. The thing that makes me believe he owns this car is that he brought up me checking it out for some wiring recall.
I don't know that more explosive is quite the right terminology so much as more volatile. The explosive force will be roughly the same, it just takes less to encouragement to explode. As mentioned, octane isn't a measure of quality of gas, but there are higher quality gasolines. Those with too much/too few/too shitty of detergents added will muck up the insides of your engine's naughty-bits. Vehicle manufacturers have put together a list of approved gasolines based on this and similar factors, and most major gas-stations (BP, Exxon, Mobil, Shell, etc) are on the list of good-gas places. I'll see if I still have the issue of Car and Driver where I found that when I get home.
In most modern cars (within the last 5 or 6 years at least), your computer will adjust settings in air/fuel ratios and timing, so putting in better or worse gas will be counteracted. As an example, my Civic says to use 87. Using 91 won't get me anywhere because the timing will be adjusted and any boost in performance will be negated. On the other hand, when I had my Z, I could put 87 in it, but the ECU would de-tune the car and I wouldn't get all of the horsepower the engine could offer.
There would be no boost in performance to negate. In fact running a higher octane than recommended will have no effect at all except to cost you more money at the pump. The ECU won't do jack-shit because the timing-adjustments are triggered by detection of engine-knocking, and running higher octane gas than required will not cause your engine to knock. Higher octane gas does not contain more energy, it simply doesn't ignite as easily allowing you to run higher compression (because compression and a bit of heat alone can detonate fuel, see: diesel engines which use glow-plugs rather than spark-plugs). Running higher compression does allow you to generate power more efficiently (allowing you to generate more power from the same amount of fuel). And just because the ECU adjusts doesn't mean you should switch back and forth all the time, because that fucks shit up on its own, you should pick one and stick with it, ideally the octane-rating recommended by the manufacturer (for maximum power-output and fuel-economy). Simply running higher octane gas does not generate more power even on a carbuerated engine unless the engine is tuned for higher compression, in which case running too low octane causes premature-detonation (knocking) which fucks up your engine because everything is supposed to happen at exactly the right instant so that forces are nicely balanced across the crank.
Just do what you're told and everything will be better in the end.