Do You Avoid Buying Gas When...

[Ronald Blue]

The biggest problem with deposits and fouled plugs was from the lead in the gas and carburetors being poor at ideal fuel mixtures especially for rare highway driving. Back in my youth, drag-racing friends used to buy high premium gas across the border in the US because a certain station on the way to the strip had higher octane gas. Idea was to be able to fudge the timing a bit more without pre-detonation and presumably get more power.
Nowadays, I hear some people talking about better gas mileage and maybe power if they use premium gas. Personally, I take the more power part with a grain of salt and a typical care has more power than it needs no matter what it's running on. A Google search says premium is generally 20-25% more expensive than regular and I doubt anybody is getting that big of a mileage increase to justify the cost.
IMO, just look in the little book they gave you, you know, the one you used to setup the radio presets, and find the headlight switch, and see what the manufacturer tells you to use.

While premium is recommended in my torch red mid life crisis two seater it does just fine on an 87 octane 10% ethanol blend. What I find most impressive is that if I drive it without having to feel those 460 HP it will average 30 MPG. It's hard to go for a cruise and not at least tickle the throttle though a few times. I tried premium and saw no improvement either in mileage or performance. It might be something you would have to go to a track to see though.

[Bill George]

Your engine has Knock sensors, when you use a cheaper gas your on board engine computer module ECM adjusts the timing to get rid of the low octane knock before you even hear it. You lose performance of course that you would have with the higher octane fuel. Continued use of low octane may or may not damage your engine.

[Jim Becker]

Your engine has Knock sensors, when you use a cheaper gas your on board engine computer module ECM adjusts the timing to get rid of the low octane knock before you even hear it. You lose performance of course that you would have with the higher octane fuel. Continued use of low octane may or may not damage your engine.

Characterizing 87 octane fuel as "cheaper gas", despite the fact that the cost is lower than higher octane fuels, just promotes the myth that so-called "premium", higher octane fuel is better or provides more power (it does not), etc. The fuel vendors don't help with this in their marketing, either. The higher octane fuel is only better if the tune of the engine can take advantage of it. One should generally use the fuel that provides for the octane requirement that the vehicle manufacturer, but as you note, modern vehicle electronics do adjust timing for fuel characteristics. I believe that in most cases, any risk of damage is minimal unless it's a super high performance engine with very high compression ratios.

For the Grand Cherokee I owned previous to my current Subaru Ascent (and the previous Subaru Ascent), the manufacturer stated in the manual that 89 octane was recommended for best performance with the 5.7L HEMI V8 but that 87 octane fuel was just fine. My current vehicle has a 2.4L Turbo four and run on 87 octane fuel. COBB has done significant testing on the vehicle/engine and determined that there is zero benefit to running higher octane fuel without a custom tune. The additional detergents that are often in "premium" fuel might offer some benefit, especially for someone running hard, but otherwise...the only benefit to buying the "premium" fuel is to the vendor's profits.

This thread really has gotten off the original question and dialog...

[Jim Koepke]

This thread really has gotten off the original question and dialog...

Though it may have stumbled on something less obvious.

There was a comment about high volume stations needing to receive refueling more often than low volume stations.

My thoughts are a station likely doesn't sell as much of the premium grade fuel as regular grade, thus needing fewer visits from the refueling truck. This would then be a factor in the premium grade being stirred up less often.

jtk

[Pat Germain]

The additional detergents that are often in "premium" fuel might offer some benefit, especially for someone running hard, but otherwise...the only benefit to buying the "premium" fuel is to the vendor's profits.

Premium fuel doesn't have any more detergents than regular or midgrade. Decades ago oil companies attempted to cash in on premium gasoline by putting better detergents into it compared to regular and midgrade. The EPA soon intervened and banned that practice. While additives packages, which include detergents, do vary between gasoline brands, there is a minimum required by law to maintain engines.

[Bill George]

Of course higher octane gives you more power in the engines designed to use it, otherwise there would not be different grades of gas. When you use a lower octane fuel in a high performance high compression engine the ECM has to retard the spark to prevent knocking at times and you do not get the rated HP. You may not feel it in the seat of your pants but a dyno will show it. Air craft engines use 100 octane for a reason. Using premium gas in a low compression engine designed to run on 87 octane will not give you more power. Yes 87 is cheaper gas than premium grade and is for a reason. Try pricing aviation gas. There are three grades of gas according to the EPA.

For fun look up Top Tier gas, it goes over and above the Minimum EPA requirements for detergents and other additive's.

[Jay Bryant]

I probably wouldn't give it a second thought if I needed fuel and a tanker was filling the station's tanks. I suppose it's the cautious thing to do, but then if I was worried about stirred up contaminants I should ask them when the last time their tanks were filled. How long does it take the fuel to settle. However, I now refuse to buy gas from a station with a reader board showing a cash price, because around here their unposted credit card price is 10-15 cents/gallon higher.

[Jim Becker]

Of course higher octane gives you more power in the engines designed to use it, otherwise there would not be different grades of gas.

Sorry, but the higher octane simply burns slower to help control pre-ignition. It, in itself, doesn't provide any more "power". But yes, a high compression engine that is designed to have a lot of power can only do what it does when the higher octane fuel is used so that the gas doesn't "explode" too early in the piston cycle for each cylinder. How things get said matter because there truly are a LOT of people that think buying "premium" high octane fuel is going to make their VW Beetle perform like a Lambo. Really. They do.

[Tom M King]

We have a local dirt race track and several stations that sell race gas. I saw some guys putting it into their stock Harleys one day. I knew the guys so asked them why they were buying race gas for those bikes. They said to get more power. I told them the only difference they would see was that it would turn their pipes blue.

[Edward Weber]

These folks do this for a living
https://www.caranddriver.com/feature...dodge-charger/
"Premium" fuel can make a difference, it's not a black & white issue.
You need to decide for yourself, with your engines and not believe everything you hear.

[Jim Koepke]

How things get said matter because there truly are a LOT of people that think buying "premium" high octane fuel is going to make their VW Beetle perform like a Lambo. Really. They do.

People will believe what they believe and trying to get them to see it a different way is so often a waste of time.

You can lead them to reality, but you can't make them believe it.

jtk

[Bill George]

These folks do this for a living
https://www.caranddriver.com/feature...dodge-charger/
"Premium" fuel can make a difference, it's not a black & white issue.
You need to decide for yourself, with your engines and not believe everything you hear.

So the new cars adapt to different octane gas by means of the ECM changing the ignition timing and perhaps even the variable valve timing and do create more effective HP on higher octane fuel.

[Ronald Blue]

The article shows if you have a BMW M5 then some form of premium is probably required. But it's basically a street legal race car at $130,000. Funny the F150 showed significant differences when fuel was changed to premium. Because they absolutely recommend straight regular for them. So obviously they aren't concerned about knocking. In fact the senior leader for engines from Ford said that in the paragraph at the end.

https://media.ford.com/content/dam/f...-TechSpecs.pdf

Actually when I double checked it says premium recommended but not required for my Corvette. So no issues. If I was going to the race track I'd definitely make sure I was using premium fuel.

[Tom M King]

I thought it was most interesting that the performance of the Honda went down with premium, but got a hair better fuel mileage from it. I guess the computer makes no adjustment to take care of the difference.

[Jim Koepke]

My truck runs on diesel, only one grade of that at most stations.

I have found different varieties and claims at different stations.

Have found stations that carry 100% biodiesel, some with pure fossil diesel and most contain 5-15% biodiesel.

jtk