Everyone is an expert
Back on April 1st, Matt posted an entry about an e-mail I had sent him about the danger of using high octane fuel on his car. The story went something like this:
- He updated his status on Twitter saying that it was his car's birthday and he was giving it premium gas as a "present."
- I read this update and wrote him an e-mail about why this is a bad idea.
- He asked if he could blog about my e-mail and I approved.
- He posted the blog entry on April 1st and got a ton of feedback, most of it disagreeing with my advice.
I just got around to reading all of the comments today, and I have to say one thing is for certain: there is a ton of misinformation out there about octane ratings in gasoline. The Internet doesn't help this one bit.
Now in the U.S., putting premium in an average car usually means putting 93 octane gas in an engine that is rated for 87 octane. "Octane" doesn't mean exactly the same thing in Europe, but the relative comparison between the two numbers is the same. I told Matt that this "premium" gas would only burn hotter in the engine and actually wear it out sooner, while providing no performance improvement at all, and advised him not to use it. I was obviously putting myself on the chopping block because I was claiming to be an expert, but this was what I was taught and I believed it.
Still do.
If you actually sit and read all the comments, you will find that
- Most people agree that using a higher octane is a waste of money. A few people claim they notice a performance improvement, but not even the gas companies could produce studies that prove this. Just read the FTC page on octane ratings:
… in most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner.
And about the gas companies not being able to prove this, you can check out the FTC vs. Exxon agreeement from 1997, where Exxon failed to produce any proof that high octane = better performance, and were forced to stop advertising their "premium" gas as better performing. - Hardly anyone agrees that high octane gas can hurt your engine. Aside from a lone commenter, John, who said:
I read several studies on this. Depending on the quality of your engine, and your driving habits, if you give your car higher octane fuel than it is rated for even once every other month, you can reduce its life by as much as 10%.
… everyone else claimed that I was completely wrong about the dangers of high-octane gas, and some even encouraged Matt to continue his gas-gifting practice. There was also some talk about on-board computers coming with modern cars that can detect higher octane gas and adjust to it, but I think people put way too much trust in computers nowadays. You can't just assume that because the manufacturer claims they are giving you an embedded system that will tailor to any octane rating you pump, that it will actually do what they say, and you definitely can't assume that "adjusting to a different octane" is the same as "preventing any harm caused." - I was probably wrong about the idea that high octane fuel burns hotter… it's more likely that it burns "cooler," and clearly octane is about compression and not heat.
- Most importantly, no one, not one person, claims any sources to backup their arguments other than Wikipedia or Howstuffworks.com.
Now, what I was taught about octane ratings as a kid was proof enough for me, considering that it came from a former mechanical and aerospace engineer who spent most of his life working on cars, but I decided to do a little investigation of my own and research the topic with Google. Unfortunately, the underlying problem to my approach was apparent right away… the results I got from Google were all made up of Wikipedia and a bunch of social answers sites like Yahoo! Answers; basically, anyone and everyone on the Internet telling everyone else their "facts" about octane ratings, without any proof or credible sources to back them up. Just as I failed to show any level of credibility when I e-mailed Matt, everything I was finding on the Internet amounted to hearsay and speculation. For a subject like octane ratings where there has been a ton of misinformation and argument in the past, this is no good.
I found a good, short discussion at everything2.com on octane rating, this snippet being in agreement with what I know about high octane fuel in a low octane engine:
The key difference between different fuels is that higher octane fuels are harder to ignite, and they generally burn cooler. That, in turn, lowers cylinder temperature and decreases the likelihood of preignition. If you're talking about a high compression sports car engine, that's the reason for higher octane ratings. But if the engine in question is a typical sedan or van (or whatever else) engine, chances are it has relatively low compression. And if you're using high octane fuel in a low compression engine, not only will it be harder to ignite, but the chances are good that it won't burn as fully. Incomplete combustion will leave nasty carbon deposits in your engine. The thing about carbon deposits is that they retain heat much better than metal does and they decrease the combustion chamber area, thus gradually increasing the compression ratio. That means you've got a higher compression, higher temperature cylinder. And this, of course, will require higher octane fuel in order to prevent detonation.
Unfortunately, this explanation is devoid of any links to actual articles or test results, so it wasn't the end of my search. It also isn't exactly like the simple explanation I gave to Matt, but it follows the explanation behind why high octane fuels cause low octane engines to burn hotter, and eventually wear out. Engines are designed for a certain octane rating and their combustion processes are designed to expect a certain burn time; modern engines with computers might modify the length of their cycles to adjust to a different octane, but that's gambling on someone else's code. If an engine doesn't burn all the fuel because it isn't designed for that fuel, you get deposits in the engine that contribute more heat and cause the engine to burn hotter and wear out faster. There aren't many studies that corroborate this, probably because oil companies wouldn't like them, but I did find this abstract from An experimental study of the effect of octane number higher than engine requirement on the engine performance and emissions which states that "results [on engines with carburetors] show that using octane ratings higher than the requirement of an engine not only decreases engine performance but also increases exhaust emissions."
Sports cars might perform better with higher octane fuel, but the engine in a sports car isn't designed to last a long time. A race car gets a new engine rather often; you can't treat the car you depend on like those.
As for premium gas having "special additives" that are healthy for an engine now and then, all gasoline is required to have cleaning additives that prevent deposits left in the engine. See the Chevron Techron page for proof that all gasolines have the same additive; just because the sign at the station implies that only premium gasoline gets additives, this is not the case. High octane gas doesn't clean an engine any better, despite what the marketing may say. If someone wants to really clean their engine, their are other ways of doing it.
And something I hadn't even thought of is that high octane fuel is more harmful to the environment, because it requires more oil to produce. This is from the National Safety Council on Energy Efficient Driving:
Do not use a higher-octane gasoline than your vehicle's engine needs! Higher-octane fuels are more harmful to the environment because they require more crude oil to produce than lower-octane fuels. Many people don’t know that most vehicles today do not require high-octane fuel (which costs more).
But I'm still on the lookout for more articles and test results that actually support what I'm saying here, because the crux of the matter is not about who was right in this back-and-forth at Matt's site. The real issue is something we have all been guilty of as web users; the tendency to act like an expert on everything and make claims without sharing any evidence. I'm trying to make up for that here by giving articles that actually support my claims, articles that have a lot more credibility than just a page of Wikipedia. After all, I think I've made it apparent that you can't trust everything you read on Wikipedia, and not everyone is an expert, not even me.
And if you don't care about any of that, just promise not to use a higher octane than you need to. One way or another, it's a bad idea.
Unless you have an engine that is rated for it… likely if your engine has a turbo injector you will require high octane according to the manual. But ya the science is missing. I would like to know why that low octane gas in my 2.3L Turbo engine lowers the mileage so drastically but I didn't notice any different in the 2.0L engine I had before that.
The documentation for my VW GTI states that premium gas is recommended, but regular unleaded can be used as well.
From everything I've been told — and this includes the NPR show "Car Talk" — modern cars will adjust to any-octane gas. But cars made to run at higher tolerances (turbos, supercharged, etc) will get better performance with a higher octane gas.
I should also add that my car is a 2.0L turbo.
When i used to work at a service station and asked my manager what the difference was and if it was good for a car, she said that the high octane fuel was also cleaner and if you occasionally put it through your car, it would make the fuel filter etc. remain cleaner and last longer.
But then again, im not the best source cause i wasn't exactly there to learn about fuel as much as i was for a quick buck
Just my 2c
Patrick, Jesse: It's true that modern cars will adjust to any octane, but this doesn't mean that you should put just any octane in there. The adjusting is intended for situations when you can't get the octane gas your engine is intended for. In daily situations when you do have a choice, you should stick to the octane the manufacturer recommends.
Sounds correct to me…
It's the truth, man - everyone's an expert, everyone's a critic. Why people don't take everything they read with a grain of salt in a many-to-many environment like the web is mind-boggling.
That said - how are we supposed to identify real experts online? Technorati rank and page specificity? It's a tough deal.
This was the subject of the first article I ever did on my website. Not really an article, but just a couple paragraphs poking fun at this phenomenon.
Sounds similar to another vehicle-related urban-legend I've often heard: change your oil every 3K miles. I truly believe that this is no longer relevant with todays highly efficient vehicles.
Of course, don't take my word for it, and while YMMV, the bottom line is, it's your money (either at the fuel station, mechanics shop, or dealership), so it behooves everyone to know what their doing with their vehicles.
And all along, i was just going for the cheapest gas (at big-name gas stations).
I also read all of the comments over at Matt's blog… Impressive! It almost looks like Matt is running a website dedicated to cars and engines and not anything related to the Web technologies or WordPress ;-)))
In my comment on the topic I also agreed that there is no point in putting high-octane fuel into an engine designed for lower octane, and that probably using for a long time higher than recommended octane can maybe wear the engine a bit sooner.
There's only one point with which I disagree, and this is the question of power.
According to my personal experience with an old car of mine (see my long comment at the Matt's blog), higher octane fuel gives a little bit more power! Yes, it's just a little bit, but there is a difference. 5% or 7%, this is not much, but still it's something.
In my case, it was that the car was able to reach 150 km/h instead of 140 km/h (it's rated maximum speed), on the same road, in the same condition. You can calculate the percent for yourself:)
Apart from that, I agree that it is not very wise to use higher-than-recommended octane number fuel every day.
Cheers, Michel
PS Proud owner of a bicycle, but a car driver some time ago:)