Comments on: Why High Octane Doesn’t Matter (Unless It Does)

By: JR

JR — Fri, 06 Jan 2012 03:08:11 +0000

Does the 89% octane fuel produce less carbon after ignition than the 87% octane.. Please reply.

By: Andy @ Retire at 40

Andy @ Retire at 40 — Tue, 16 Dec 2008 19:19:47 +0000

This post has been featured on the 89th Carnival of Money Stories at Retire at 40. I too have never seen the point of putting higher octane in your car. When I first bought it, someone told me this and I've kept it with me ever since.

By: Chris

Chris — Tue, 16 Dec 2008 00:18:03 +0000

While this is accurate, it is important to consider that you can use lower octane fuels without harming your car if needed.

Modern cars utilize a computer to retard ignition timing if sensors indicate that the fuel is detonating early (aka knocking). Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency. So putting a lower octane fuel in your car will actually reduce your efficiency (and probably require you to purchase more fuel per mile driven) but will not harm your engine over the short term.

By: Patrick

Patrick — Thu, 11 Dec 2008 15:23:23 +0000

Back when I was in high school, I had a firebird that required 91 octane. It was really hard to put more expensive gas in my car considering I really didn’t have much money at the time. At least now I have a car that uses lower octane gas and is much more fuel efficient.

By: Carla

Carla — Thu, 11 Dec 2008 07:17:27 +0000

Its good to know that I’m doing the right thing by putting 91 in my car (that actually requires it). Its an ’07 Acura TL S and I know my SO would kill me if I put anything less in it! I will be glad when we move out of the area and sell it though! Its a great car, but selling it means one less expense for me and pollutant on the road.

By: peter

peter — Wed, 10 Dec 2008 21:57:30 +0000

I have a 97 ford explorer that was starting to idle terribly and almost stall. I kept pondering what repairs would need to be done on it, then i decided to try super unleaded. It now runs and idles great – doesn’t feel like it will stall. For this older car, better idling means paying a bit more at the pump and not paying a shop.

By: Miss M

Miss M — Wed, 10 Dec 2008 19:50:40 +0000

It’s another thing to consider when buying a car, whether it requires premium, since that will add to the total cost of ownership. I bought a car that requires premium (turbo), when gas neared $5/gallon for premium I was starting to wish I bought a car that ran on 87.

By: jim

jim — Wed, 10 Dec 2008 19:40:52 +0000

Hahaha good point Fred.

By: Fred

Fred — Wed, 10 Dec 2008 19:12:13 +0000

Good article. minor note–the piston moves up and down inside the cylinder. The cylinders don’t move relative to the car..

By: philip

philip — Wed, 10 Dec 2008 18:37:18 +0000

When you pay the premium for the higher octane most companies also add in some other additives with it. These additives can help keep the engine clean and to burn well. It will not make for lower performance either.

Personally I like to put in a tank of mid-grade fuel once every 8-10 tanks to take advantage of this. If this is completely useless I am not certain but it is from my understanding. Kind of like shell advertises that theirs runs cleaner and does not gunk up as much, it is all about additives that are put in basically the same time they fill the truck that brings it to the stations, otherwise the stuff is all the same.

By: MoneyGrubbingLawyer

MoneyGrubbingLawyer — Wed, 10 Dec 2008 18:26:27 +0000

I can recall arguing with a guy in my high school Geography class about the merits of high octane gas. He was *sure* that his car was faster using premium.

The only exception to not buying higher octane fuel for a car that calls for 87 is if you’ve got an engine knock, a not-uncommon problem on older cars. Upping the octane level will often fix this problem. Actually, to be more accurate, it just alleviates the symptom (the engine knock) of another problem.

By: Miranda

Miranda — Wed, 10 Dec 2008 18:25:56 +0000

I never really thought about WHY I was using 87 octane, as required by my car. I always did, but we have been considering using premium. Now, though, I know there is no point.