Are the benefits of high-octane gasoline worth the price?

[Kizarvexius]

When it comes to cars and driving, I prefer practicality over style any day. I drive a Saturn wagon, which is not remotely likely to turn any admiring heads, and the manner in which I conduct my vehicle as I wend my way down the avenue is slow (read: at the speed limit) and careful (read: boring).

As I wish my vehicle to last for as long as possible, I try to maintain it to the best of my ability (which is, admittedly, not saying much). Along with regular fluid and filter changes, I am in the habit of selecting high-octane gasoline during the fortnightly fueling ritual.

My question is this: are the benefits I gain by filling my tank with supreme unleaded worth the extra money I am paying? Again, I am not a performance driver, and my car is a 6-cylindar station wagon. Am I doing something good for my car, or wasting money?

[barbitu8]

http://www.cartalk.com/content/colum...ctober/11.html

High-octane gasoline is of absolutely no benefit to the vast majority of cars on the road. You should only use high-octane fuel if your owner's manual specifically recommends it.

[Early Out]

We've been down this road before (at a stately 55 mph, of course!): http://boards.straightdope.com/sdmb/...d.php?t=260826

[NurseCarmen]

The car talk guys even said that it's actually kinda bad to use higher octane on some engines because it burns hotter, which could cause damage over time.

[Telemark]

Originally Posted by NurseCarmen

The car talk guys even said that it's actually kinda bad to use higher octane on some engines because it burns hotter, which could cause damage over time.

IIRC, it isn't that it burns hotter, but that higher octane is more resistant to burning than lower octane gas. Thus, the combustion timing is off, and burning gasses may be expelled out of the cylinders and there will be flames in the exhaust manifold, where there isn't supposed to be flames.

[Kizarvexius]

Thanks for the responses so far. Looks like I'll be saving some money from now on.

So if high-octane gas is doing my car little good, and even potentially bad for it, is it more beneficial to go with the mid-grade or the regular unleaded? Does it make a difference to drivers like me, other than in terms of price?

[Chefguy]

Originally Posted by Kizarvexius

Thanks for the responses so far. Looks like I'll be saving some money from now on.

So if high-octane gas is doing my car little good, and even potentially bad for it, is it more beneficial to go with the mid-grade or the regular unleaded? Does it make a difference to drivers like me, other than in terms of price?

Read the manual. It probably recommends regular (87 octane) unleaded. As long as your engine isn't knocking, it's fine.

[mangeorge]

My car, and many others, sense the octane of your fuel and tweak the engine (timimg, etc) to match. Result: higher octane = more power. There aren't many cars, afaik, which require high octane. As mentioned, check your owners manual.
And I take the "car talk guys" with a grain of salt. They tend to be bombastic, and lean toward saying that which gets you to nod your head.
Peace,
mangeorge

[Balthisar]

This really goes for all aspects of your car. Manufacturers spend a lot of money researching this stuff. You can't even say "planned obsolence," because there's more value in your car being regarded as long-lasting than forcing people to buy new ones every three years (there are better ways to do that!).

So, brand of oil, natural or synthetic, oil change frequencies, tune-ups, and all of that stuff can be found in your owners' manual or maintenance manual (if the latter comes separately, like mine).

As a further benefit of getting to know your owners' manual, you can't be convinced to do stupid, unecessary services at dealers or shops or even quick-lube places. You know, you go for a $30 oil change, and get talked into a $125 transmission flush with only 60,000 miles on your car? Or rotate the tires every 5,000 miles?

My point is, trust your owners' manual.

[Bag of Mostly Water]

Another Saturn ower here.

When my car was a few months old, the check engine light came on. The dealer said the diagnostic code was "sluggish O2 response." They said this is generally caused by using gas with too high octane. Most likely, I hit the 89 or 91 octane button on the pump by mistake when filling up. They recommended immediately filling up again with 87 to dilute any remaining high octane fuel. The car ran fine and there seemed to be no damage.

[flight]

Originally Posted by mangeorge

There aren't many cars, afaik, which require high octane. As mentioned, check your owners manual.

I have only seen two types of cars that require it:
1) High performance luxury cars (my friend's BMW Z4 fro example)
2) My Ford Focus SVT. It is a small, relativelt inexpensive car that has a good bit of power for its size and has been heavily modified from the standard Focus for performance. I highly reccomend it for enjoyable driving on a smaller budget (though it has what I consider a less than attractive look).

[Telemark]

The general rule is to use the lowest octane gas where your car won't knock and ping. For cars that are in tune, it will be whatever the manufacturer recommends. For all Saturns it's 87.

If your car is out of tune you might need 89 or 93 to prevent pinging. If that is the case, use the higher octane gas until you can fix your car.

[Xema]

Originally Posted by Kizarvexius

As I wish my vehicle to last for as long as possible, I try to maintain it to the best of my ability ... I am in the habit of selecting high-octane gasoline during the fortnightly fueling ritual.

My informal research suggests this is rather common - a sort of "If it costs more it must surely be better" approach. As the responses thus far indicate, this rarely holds any water.

[Dog80]

Do they measure octanes differently in US than in Europe? Because in Europe the smallest octane number you can find is 95 and the highest 100.

[Gary T]

Originally Posted by Balthisar

You know, you go for a $30 oil change, and get talked into a $125 transmission flush with only 60,000 miles on your car? Or rotate the tires every 5,000 miles?

Your general point is well taken, but these are poor examples. Many cars on the road today have a recommended transmission service interval of 30,000 miles. For some front-wheel drive cars tire rotation at 5,000 miles may be appropriate.

[Telemark]

Yes, they do measure octanes differently in the US vs Europe. Europe uses RON and US uses MON, which produce different numbers. I may have gotten that backwards.

Here's a good FAQ about octane

[Gary T]

Originally Posted by Dog80

Do they measure octanes differently in US than in Europe? Because in Europe the smallest octane number you can find is 95 and the highest 100.

Yes, a different measurement is used. From here: http://www.stretcher.com/stories/01/010226m.cfm
"In the United States, pump octane is an average of 2 ratings, research octane (RON) and motor octane (MON)....Research Octane number is always higher than Motor Octane number....In Europe, they only report the RON.

[Viscera]

Related question...in this area of the country, 89 octane has 10% ethanol, and so it is normally 2-5 cents cheaper per gallon than the 87 octane stuff. I have been using that for years, but is there any disadvantage to doing so?

Vis

[Balthisar]

Originally Posted by Gary T

Your general point is well taken, but these are poor examples. Many cars on the road today have a recommended transmission service interval of 30,000 miles. For some front-wheel drive cars tire rotation at 5,000 miles may be appropriate.

You're right -- I hope eveyone follows my advice and reads their service instructions, and don't look at my examples and say, "hey, Balthisar said I don't need no stinkin' transmission service!"

(Examples from my personal experiences with my own service frequencies, although I usually fall for the tire rotation thing, since it's "only" $3.00 extra at the dealer).

[BiblioCat]

Originally Posted by Telemark

The general rule is to use the lowest octane gas where your car won't knock and ping. For cars that are in tune, it will be whatever the manufacturer recommends. For all Saturns it's 87.

I have a Saturn wagon, too (a '97), and I had always been using the mid-grade stuff, 89 octane, because that's what the owner's manual says to use. Since gas prices have been skyrocketing last spring, I started been using regular, and it's been fine. My husband commented that he had no idea I'd been using the mid-grade all these years, and that I should have been using regular.

[Absolute]

Most newer cars that require premium gas will actually run decently on regular. The engine computer can detect the change in octane level and adjust the timing and ignition settings to compensate. However, since these engines weren't designed to run regular gas, their efficiency and performance suffers. In most cases, the few bucks that you save by skimping on premium is more than made up for by the fact that your gas mileage drops in half.

The feature is there basically for emergency situations: i.e. you're stuck out in the middle of nowhere, and the only gas station within 100 miles is out of everything but 87.

For cars that don't require premium, it is a complete waste of money. For a while now, Congress has been talking about passing laws that make it illegal for gas companies to market premium gas as somehow "better" than regular. The only reason it is more expensive is that the refining process for premium involves more steps.

[Telemark]

Originally Posted by BiblioCat

I have a Saturn wagon, too (a '97), and I had always been using the mid-grade stuff, 89 octane, because that's what the owner's manual says to use. Since gas prices have been skyrocketing last spring, I started been using regular, and it's been fine. My husband commented that he had no idea I'd been using the mid-grade all these years, and that I should have been using regular.

That's very odd, since I had (just sold) an 97 SW2 and my owners manual said 87 octane. Which engine do you have? I've never heard of a Saturn recommending anything but 87 octane.

[BiblioCat]

Originally Posted by Telemark

That's very odd, since I had (just sold) an 97 SW2 and my owners manual said 87 octane. Which engine do you have? I've never heard of a Saturn recommending anything but 87 octane.

I'll have to check - it's in the car, and I'm going out in a while. I'm pretty sure it said 89. I could be wrong.

[badmana]

Originally Posted by flight

I have only seen two types of cars that require it:
1) High performance luxury cars (my friend's BMW Z4 fro example)
2) My Ford Focus SVT. It is a small, relativelt inexpensive car that has a good bit of power for its size and has been heavily modified from the standard Focus for performance. I highly reccomend it for enjoyable driving on a smaller budget (though it has what I consider a less than attractive look).

There are many cars that require 91 octane. The SVT is a turbo car and thus has a high compression ratio. My Matrix and the Toyota Celica (XRS/GTS) both also require 91 as they are high compression engines. AFAIK all Turbo cars require premium.

[trupa]

Originally Posted by flight

I have only seen two types of cars that require it:
1) High performance luxury cars (my friend's BMW Z4 fro example)
2) My Ford Focus SVT.

Add to that the Volvo V70 wagon, which requires 91 octane and the VW Passat GLX (V6, not even the W8!)

Based on our recent car shopping experience. We bought the Passat, so now we have to pay a $0.10 CDN premium per liter!

In case you're wondering why we bought it despite this, there are a number of reasons, but in short it was the 4 WD Wagon we disliked the least from those we tried...

[BiblioCat]

Originally Posted by Telemark

That's very odd, since I had (just sold) an 97 SW2 and my owners manual said 87 octane. Which engine do you have? I've never heard of a Saturn recommending anything but 87 octane.

Okay, I'm obviously a moron. The owner's manual does say 87 octane. I don't know why I spent nearly eight years thinking I was supposed to use 89.
Feel free to ignore me from now on.

[Metacom]

Originally Posted by trupa

Based on our recent car shopping experience. We bought the Passat, so now we have to pay a $0.10 CDN premium per liter! [/i]

AFAIK, all Passats require 91. I have the GLS with the 1.8T, and it requires it. Any VW car with the 1.8T engine needs it, and they use that engine in many of their models...

[Shoeless]

Another former Saturn owner checking in here. Well, actually it was my wife's car, a 92 Saturn SL2. She noticed in the summer when she had the AC running that the car seemed more sluggish, and swears that putting mid-grade gasoline in the tank made the engine run better when the AC was on. In non-AC-intensive weather she used regular unleaded.

Also, round these parts it seems like the mid-grade gasoline is usually the 10% ethanol blend. Seems like I remember hearing somewhere (Car Talk?) that the ethanol has a tendency to dry out rubber parts like hoses and gaskets and stuff.

[mangeorge]

Some have advised listening for pinging (and knocking) as a guide for which octane you need. Hmmm, a little caution here might be a good idea. You might not be able to hear these sounds, especially in a higher end car and especially if your ears are muffled by the desire to save money.
Pinging is Bad For Your Engine, period. Pinging is pre-ignition, which blows holes in pistons if not corrected. The sound is an explosion that occurs on the upstroke of the piston. If your engine pings during normal driving, or at all in most newer cars, and you are using the reccommended octane, there's something wrong.
I doubt that car manufacturers get a kickback from oil companies, so there's little incentive for them to fool you into using a higher octane than your car needs.
Bottom line; know what the cost is before you buy and buy a car you can afford to drive.
Yeah, right.