sbasaria

Interesting questions, i just bought a second hand 2002 TL S type and have only put premium. I am also curious as someone told me that a check engine light may come on with use of 89 Octane. Havent tried it as yet but dont want to take a chance. Any words of wisdom?

MichaelkTSX

CEL doesn't come on in a 2nd gen TL if you use <91. That someone is an idiot.

hawaiiantsx

it also says it may be dangerous to operate vehicle while intoxicated or under the influence of alcohol

crfortin

let me join in again ...

The fuel recomendation up till now is 91 for optimum performance. That means heavy reving without fear of knock.

93 Octane will not make your car go faster. You will get lower mileage.

89 will not damage your 04-05 TSX. Canadians are told they can use it with lowered horsepower. You might get the same mileage or better.

I baby my baby with 91 octane(where sold), Mobil 1 Synthetic, and Stealer Service.

that doesn't mean that doing otherwise is bad. The premium chaged for premium in canada is outragous ~20%. When gas prices were high this was amounting to real money.

If you are feeling cheap and plan to be puttering around town without heavy VTECing for the time being you can go 89 IMO. It's a valid economy measure.

It is vaugely plausable that the 06 with the new higher cuttoff point and a higher airflow could be more susceptible to knocking if you have a lead foot. But I think a LOT/Most of premium gas is burned under conditions where there is not even a remote possibility of actual knock.

- Chris

PS. Oil company conspiracy was a nice touch.

R J Poseidon 6

U should've asked if he wanted 2 run!!!

Accurate

I wanted to point my gas nozzle towards him and set him on fire.



(i would eventually put it out)

Actuary

If you aren't racing and no heavy load in vehicle, 89 and 87 are all good.

Now if you are going on a mountain with 3 people on board.. you better put 91 because your car might get ass kicked by a diesel pickup truck. Those things are beast coming out of curve accelerating where I am long way to go to hit VTEC.

Ellas9

My two sense:

10.5 is not necessarily a 'high compression' ratio which requires premium....V6 Accord Hybrid has a 10.5:1 ratio but recommends regular octane- 87.

I bought the car a few months ago and during the winter I will keep using the recommendation but I will experiment with 87/89 in the Spring.

Also, higher octane gas is not necessarily cleaner (Canadians: Shell and Petro put more detergent in higher octane fuel but Esso and Sunoco do not).

Some guy did an amazing fuel test (search forums) and found better efficiency with higher octane fuel on highway.

The 05 manual or quick reference guide (can't remember) also says that lower octane can damage the engine. Overall, I think premium is a marketing ploy (i.e premium brand = premium fuel; Accord V6 Hybrid is to lower fuel costs hence regular recommended) but I buy what someone said in this thread whereby the knock sensor may be overworked with lower octane fuel and fail early.

sauceman

I wouldn't be surprised to lear that Honda has corrected their aim, given that the K24A2 can be a serious oil consumer as the engine ages on, and the consequences of oil burning can be amongst other things carbon buildup that would favor pre-ignition, even with a retarded timing.

There is no change in the CR, but the increased airflow may well alter the dynamics of the engine to the point that it could be more prone to knock.

ilitig8

FYI, the US website still has the "will lowered performance" phrase for lower octane fuel for the 06 TSX, there is a mistake somewhere, my guess is that the true octane requirement has not changed, but who knows.

Bucketboy

Did a quick check of the 2005 sales brochure I picked up while car shopping. Page 26 lists the recommended fuel as "premium unleaded 91 octane", with a reference to footnote #8. At the bottom of the page in the fine print, footnote 8 states "Gasoline with an octane number lower than 91 may be used, with reduced performance". However I still use premium.

Brandon24pdx

I'll vouch for this. For the first 75-100 miles or so of my "dealership tank", the engine felt nice and strong, but after that I could tell that the ECU had seriously reduced the timing advance. (The acceleration felt soggy and weak).

This happened of course because the knock sensor had detected enough "counts" of knock on the cheap gas to scare the ECU into switching to more conservative timing maps, thus not damaging the engine.

Little known fact is that the ECU in most any modern high compression/turbo/supercharged engine will very frequently be detecting small amounts of knock here and there, even while using premium gas. If you saw how much more knock was being picked up by the ECU when using cheap gas, you probably wouldnt use cheap gas anymore. (You could see, but you would have to have some sort of datalogger or a standalone ECU.)

Does cheap gas hurt a TSX engine tho? Theoretically no, because the ECU can compensate fairly quickly based on how much knock it hears through the sensor, but the knock has to be there in the first place for the ECU to react to it. Over the long haul (like 150k miles) using cheap gas, or switching from premium to cheap often would cause the engine to see more knock in its lifetime compared to an engine that only burned 91+ octane. More knock will slowly but surely nibble away at the head gasket and piston rings faster than the engine that saw very little knock. I can only assume this is what Honda is alluding to when they say that "engine damage could result if you use lower octane fuel." I highly doubt you could get a factory honda engine to "blow up" if you accidentially put cheap gas in and drove it hard...they designed them on purpose not to do that. Still, you could cause longer term wear, and thats my long-winded explanation as to why you should listen to the manual and use the kind of gas it tells you to use. (some wont care if they cause long term wear if its a lease or whatever...thats not my personal philosophy, but do what you want.)

Knock sensors do wear out over a long period of time, yes, but as far as I know, not because they've "heard enough" They're just an electronic device, a microphone, usually dampened by a goo or jelly. Over time the goo/tar can leak or seep out of place and cause the sensor to be overly sensitive. I suppose its possible the electronic components could lose accuracy. (I replaced the original 10 year old sensor on my old Eagle Talon when I had it.)

peter_bigblock

I'll bet this: if your TSX has engine problems that a dealer can relate to use of lower-than-91 octane gasoline, they won't honor a warranty claim if the manual makes any claim on any page that doing so will harm your engine. My guess, that's the impetus for the change from 04/05 to 06. And telling them that the salesman said it was okay three years ago is going to get you bupkus.

I'd never rely on the knock sensor (a protective measure) to keep my engine running properly. If you need to save a few hundred bucks/year, skip lunch one day/week. You'll save about $500 and you'll lose a little weight.

I understand saving money (hell, I built my own CAI out of spare drain pipe parts to save a few bucks!). It isn't a conspiracy. The Acura engineers don't hate you. Put the proper gasoline in your car.

biker

But that's thing - Sauceman has shown that you DON'T save any money putting regular instead of premium. The lower gas milage with the cheaper gas offsets any gains by using the cheaper gas.

sauceman

True. From what I've seen during my tests, you will consume 6% more gas using 87 than 91.

https://acurazine.com/forums/showthread.php?t=23721

peter_bigblock

If 6% less is what one might expect, then the savings (assuming a price spread of $.25/gal) at 15k mi/yr is about $75, or $.20/day. Peanuts for someone who's driving a $28k car.

crfortin

Sauceman,

don't mean to impune your testing skills which are formidable but I just don't belive the 6% decrease in fuel economy with 87 figure. Not if the car is driven moderately anyways. There's more energy in the 87 fuel and thermodynamically MORE of it should burn at the same temp, unless you were WOT knocking the whole trip or the ECU is really freaking out and chokeing off the air.

Glancing at your results the thing that stands out to me most is the temperature. 13C vs 20C. That alone could cause a 6% reduction in fuel efficency. Cold or hot weather murders fuel economy. There are simply too many other factors to account for air pressure, humidity, & avg opposing wind speed is difficult to judge inside a car.

Was fuel weight taken into account for all times and cases ? Full tank adds 3% to car weight.

Respectfully,

- Christopher

sauceman

What can I say? I tried to conduct this test the most accurately I could, and these are the numbers I came down to.

As I mentionned in the thread, those factors you point out to me, I've taken them into account, and I would venture to say my estimations were pretty precise:

themayor

Is this really true? Lower mileage? Why would a slightly higher octane produce worse gas mileage?

So far the only choices I've seen here in Columbia, SC is 87, 89 or 93. That was after checking 4 stations, I've only had the car a week so I don't know if anyone around here carries 91.

Tim

gsclifton

iTrader: (2)

Chevron Premium (93) = $2.17 over the weekend. I see no issues with using Premium over Regular (87) in the first place.

rb1

This is quite possible. The higher octane causes the gas to resist detonation, and the timing in in cars designed for 87 octane gas is delayed compared to those that are designed for octane 93. This may result in the fuel combustion peaking at the "wrong" (well, less than optimal) time.

The moral of the story is that that you should use gas of the mininum recommended octane level for your car, at least while it is new. (The rules change somewhat once you get 150K+ or so miles on the engine, then sometimes you need a wee bit more octane to avoid engine knock).

themayor

So I'm SOL? I assume using 93 (although not optimal) is better than using 89?

Kighter

We don't get 91 here in the south themayor. What you need to use is AT LEAST the octane recommended, so 93 is fine. If you see 91 somewhere that would be fine to use.

rb1

Exactly.

I was just pointing out that it's silly for someone with a new car that is timed for 87 octane to put 93 in it, and it is quite possible that they might even get worse gas mileage on 93.

themayor

that all makes sense. thanks for the input guys.

just looking to baby my new baby.

Ellas9

I was talking to an engineer at General Motors in Oshawa, Ontario and he shed some serious input into this discussion.
I'll get to the point first. He said, and I agree, that all GM production engines (event the Vette high output variants) and to his knowledge most all Honda engines could run on 87 without much knock or other damage. He believes based on the specs of the 2.4 in the TSX that a "proper" 89 octane would likely be the most efficient fuel. He doesn't believe that fuel stations actually mix the 87 and 91 properly to achieve 89 octane so that's what he meant by proper.

He said, and I agree, that 87 burns with much less compression required. As such, the exposion could be fully accomplished BEFORE TDC-top dead centre (compression/power stroke). This means that the momentum of the piston (and crankshaft and other pistons moving in time) which was still moving up on the compression stroke will suddenly shift from up to down (before TDC). That's against the momentum of the engine. That's worse then you running into a wall. In this case, your running into the wall and the wall is also moving toward you! Therefore, the pressure on the crankshaft is immense. A knock sensor simply changes the timing to try to allow TDC (I believe through the crank position sensor) to agree with the explosion as closely as possible. On very high compression (usually the Euro makers) the above story is very possible if revving high and over some mileage. He thinks the TSX is not so aggressive with timing and compression to allow this to happen. He said that 91 (I'm talking Canadian measurment) would likely be too much octane because our compression is not high enough to faciliate a 100% 91 octane burn. On this, I think a test needs to be done to see if indeed the 89 is best for efficiency. Overall, I won't go with 87 based on this discussion and I will test 89 in the Spring. This is an important discussion to us in the GTA because 91 octane is almost 11 cents per litre more than 87.

crfortin

if only 93 and 89 were available I guess the best option would be to mix. You could throw some 89 in every second tank.

I can post this all day and I'm sure that there are some people won't belive it. Higher Octane fuel contains LESS energy by volume. Octane is merely a measure of knock/predetonation resistance.

There are two ways to raise the ocate by my understanding. Refine the fuel for the the lighter shorter hydrocabon chains, the more "octane -8 carbon chains" or lengths close to that. The shorter chains contain less total energy than the diesel like chains ~avg 20+ length. The other tactic is to use a nice engine coating Mg+ based cancer causing additive. Most mid-high fuels use a combination of these tactics. The additive doesn't burn(if fact it's job is to reduce early burn), but still takes up space/mass in solution (2-3%?).

We associate just octane with speed because it's used in high-rev, high compression engines.

The think the highest octane fuel ever was the Jet Fuel used for the SR-71 Scramjet engine. Where the fuel/engine/storage area would heat to hundreds of degrees due to air friction. I think the additive was some rubber-like compound or something. It cost more than scotch/whiskey by volume and You could reportedly drop a lit match in a tub of it without it ignition taking place.

The really exciting research going on with Honda is the direct injection + compression ignition for gasoline engines. A 40% increase in total efficency for the 100 year-old technology of ICombustion may in fact be possible.

gomez_regina

Having to use Premium shouldn't really come as a surprise...Premium was required in the 2004 TSX as well; that's actually one of the things that led me to trade in my TSX. When Premium gas is all of the sudden costing $1.25/Litre and it's costing $65.00 to fill the tank, it's time to move on!

Brandon24pdx

You cant hurt the engine with octane thats "too high," if the choice was either 89 or 93 and the car is recommended to run on 91...use the the 93. (Actually 92 is premium in the pacific northwest, so it kind of depends on what region of the country you're in).

Hell, if you wanted to you could burn Sunoco GT 104 or Unocal Comp 100 and it wouldnt hurt the engine...theyre still just unleaded gasolines. (Leaded gasolines for racing would be a no-no for O2 sensors and catalytic converters...)

The only side effects of running super high octane would be a slight decrease in fuel economy, and the car would be more hesitant to start on a cold morning. However, it would be a waste of money spending $5/gal to burn Comp 100 in a stock TSX engine...just trying to make a point that "too much octane" is a rediculous idea for all intents and purposes. I suppose if you could make a fuel that had an octane rating of 200, that would be "too much," since the car probably wouldnt even start. (thats why you cant burn diesel in a gas engine...to difficult to ignite.)

If youve got a built turbo engine like a supra or an EVO VIII, octane is everything in regards to making horsepower.

vidgamer

Here, premium never (?) seems to be more than $.20 more than regular a gallon. So, the higher gas prices are, percentage-wise, the better deal high octane seems to be!

So, what is that at current prices, like 9% more only to have (according to the aforementioned tests) 6% less? No, I'm not going to worry about 3%. The percentage was less than that when prices were goign crazy not long ago.

I recently was riding in someone's Pontiac -- a nice sporty 4 door with leather seats, etc. The computer said that the MPG was about 16. 16! My TSX is getting 40% better milage in town! Wow.

Plus if you're modding to use more power, it seems counterproductive to worry about saving a few percent... Which do you want? Our cars already get good milage if driven moderately, yet give good performance when you rev it. The best of both worlds!

This would be my main concern, thus I'll continue to use premium.

bradykp

that goes against what i've been taught. 93 octane in my 91 nissan sentra which doesnt need higher than 87 would hurt that car. would it be large damage? no, but overtime, it is bad for the car in this case. 93 vs 91, i don't think is as drastic. but yes, you can have too much octane for a car.

majorbike

I'm new to this forum. I'm looking at a new car and the current favorites are the TSX 6 speed or the new Accord V6 6 speed sedan. One of the things is that the Accord uses regular gas and pumps out 244hp. My gut feeling is the Honda will accerate faster, but won't have the handling.

One sales coordinator at our local Acura dealer said that no one at the dealership that she is aware of uses premimum. They all use plain old 87. Most places here in Missouri don't have 91, just 87, 89 & 91.

Brandon24pdx

The new 6MT Accords are nice...I have no idea if they require premium gas or not. 244HP out of a V6 is starting to get up there though. The more power a manufacturer wrings out of an engine, the higher the octane you would need. (buddy's G35C is a ~290 hp V6 and does require premium.)

excited

87, 91, 92 and 94 octane fuels are available here.

Here are some sites with some info on octane and engine performance:

To summarize what they say is:

Using a higher than necessary octane level adds no benefit.

Using a lower than required octane level will affect fuel economy.

The detergents in the fuel maybe more important. Honda recommends using a "Top Tier" fuel supplier.

http://auto.howstuffworks.com/question90.htm

http://www.toptiergas.com/

http://www.canadiandriver.com/articles/jk/040728.htm



Excited

majorbike

This is a foollow up post on the V6 Accord with a 6 speed. This afternoon I got to drive one. Lots of go and basically the same nice transmission as the TSX. The brochure says the compression is 10:1 and it takes regular gas.