I10O0I1

iTrader: (1)

i always use 91.. and sometimes 89 but never 87

dzuy

93. shell.

VeniceBeachTSX

Actually, your engine makes better power (and needs the octane more) when the weather is cold and the air is denser. In hot weather or high altitudes, you lose power and octane becomes less relevant.

JTso

iTrader: (2)

This might be true for NA application due to the OBD2 ECU's IAT circuit to add fuel and timing when air temp is cold. It reduces fuel and timing when air temp is hot. However, when the engine is running FI application, you will need the highest octane available regardless of outside temp due to the increased cylinder pressure and air temp from the compressed air.

VeniceBeachTSX

This is sort of true, but very simplistic. The thing that causes the fuel to combust is not the compression ratio, but the actual pressure in the cylinder. This depends on two things:

1) What is the pressure of the air in the intake?
2) What is the compression ratio?

Multiply these two factors together and you'll get (roughly) the maximum pressure in the cylinder prior to combustion.

(Actually, I'm simplifying here as well, because other factors such as temperature and humidity impact the liklihood of detonation, however these are all secondary factors.)

Air pressure in the intake depends on two factors:

a) Air pressure outside. If the pressure outside is low (as it would be in a mountainous area) then the maximum pressure in the intake, and thus in the cylinder is reduced. This is one of the reasons that octane ratings are typically lower in the mountain states than on the coasts. You just don't need it at altitude.
b) Throttle position. If the throttle is not wide open, the air pressure in the intake is reduced. At idle it could be as little as 1/3 of outside atmospheric pressure, at "normal" operating speeds it's still much lower than outside ambient air pressure. The peak pressure in the cylinder is similarly reduced (this, after all, is how we control power).

When car manufacturers certify engines, they do so assuming the "worst case" scenario. They consider a very cold day, at sea level pressure with the throttle wide open. They determine the minimum octane necessary to avoid detonation in those conditions and in truth, also add a bit of a fudge factor. If you're a guy like me who is never even close to WOT, then the issue becomes academic. You're never going to build up the pressures in the cylinders that would be necessary to create detonation conditions. As I said elsewhere, this really only happens at the very top of the power curve.

Incidentally, those of you using a SRAM or CAI type setup might want to consider higher octanes if available. By installing one of those in place of the normal air filter, you're reducing the constriction in the induction system, and allowing higher induction air pressures to get to the engine. This gives you a bit more power, but you are quite likely going to exceed the peak cylinder pressures considered by Honda when they tested a stock setup. Probably isn't going to make a huge difference, as they build in a lot of leeway, but the extra octane wouldn't be a bad idea.

In airplanes we usually think of 3000' at a fairly critical level. Below that, outside air pressure is sufficiently high that an engine run at WOT with an insufficiently rich mixuture is likely to detonate. Above that, a non-turboed engine can operate fine at pretty much any throttle and mixture setting because pressure is sufficiently reduced so as to make detonation impossible. At lower altitudes, just closing the throttle a bit achieves the same goal (but is generally not a good thing to do on climbout).

You learn a lot flying airplanes, where all the engine controls are purely manual and there's no ECU to save your ass if you screw up...

VeniceBeachTSX

Sorry, I have no idea what NA and FI are.

edit: Normally Aspirated vs. Forced Induction??? That would make sense in context of your comment, though the latter is not really relevant to the TSX.

kurt_bradley

Good enough for Ferrari, good enough for me. V-Power has been the only thing in my tank since it has been out. That's an endorsement from me I guess.

VeniceBeachTSX

The site says that the GT100 is the highest octane street legal stuff, and they list a few dealers in a few states. Not available everywhere, probably because of emissions stuff. The leaded stuff isn't street legal and seems to have very limited dealers.

Given what I know about the controls on leaded aviation fuel, I have to suspect that it's tough to get your hands on this stuff. And it's expensive as hell because only a handful of refineries in the US make any kind of leaded fuel anymore and it has to be completely segregated from all unleaded fuel. Can't go in any pipelines, has to be transported on a seperate fleet of tankers, etc. Basically anything that touches lead has to be completely purified before it can be used for normal fuels again.

In aviation, we're all bracing for the day when good old 100LL (low lead) fuel goes away and we all have to either replace or seriously modify our engines to work with the best available unleaded alternative. In all liklihood that's in the next 5-10 years. At this point there's only one company in the whole world that actualy manufactures TetraEthyl Lead, and only 3 ancient ships that transport it around the world. The only reason those still exist is that the environmental cleanup if you took them out of service would be more expensive than keeping them running...

teranfon

Hi

Excuse me for asking, but which dealership did you purchase your car from. I'm an Edmonton resident as well and I'm ordering a TSX within a few weeks. Any complaints with servicing or warranty issues?

Thanks

Terry

gavinn58

they have 92 out here in the 808

tsxhondatuner

ya i noticed the gas station next to the car lots have credit cards hanging on the wall "Prestige Acura" "Manly Honda" "Hansel Ford" bla bla bla and of course its at the cheapo gas station with shell right across the street, but they don't care where its from as long as its cheap for them.

VeniceBeachTSX

Just found an interesting website for people who really want technical details about gasoline, octanes, power and how it all impacts your engine. I also finally figured out why aviation gasoline ratings are different from anything else on the planet:

http://www.repairfaq.org/filipg/AUTO/F_Gasoline.html

Interesting point regarding this conversation is in section 7.1 (emphasis mine):

gpsiir

I use 89 octane. I've tried both 89 octane and 91 octane in my TSX, (can't get over 91 in Colorado Springs), and I know this next comment will generate some snorts, but I tried 10 tanks of 91, then 10 tanks of 89, and the 89 averaged about 1 mpg better (.92 if you want to be picky ). I have a theory; I know that the higher octane numbers have combustion retardants in them, to prevent premature combustion in the higher compression engines. Lower octane gas actually has more power than higher octane numbers, but can’t be used in high compression engines ‘cause it will cause an almost “dieseling” effect, and pinging. Well, I spend most of my time driving between 6700 and 7400 feet above sea level, which naturally retards combustion, so the 89 octane gas at my altitude gives about the same power as a 91 octane at lower elevations.

Flame away.

VeniceBeachTSX

At 6000' you've lost about 20% of your power (compared to sea level) due to altitude. Max pressure in a non-turbo engine is already down by about 20%. You don't need anywhere near the same octane at those altitudes as you do lower down.

The site I linked yesterday has some information about this: http://www.repairfaq.org/filipg/AUTO...l#GASOLINE_017 It seems that recent studies show that you need between .2 and .5 less octane points for every 300m of altitude (approximately 1000'). Even using the most conservative numbers you'd need about 1.5 less octane points at 6000', compared to sea level. Using less conservative test results, you might be OK even with 87 or less at those altitudes.

I suspect the real difference is in the formulation of the gas. The formulation will be adjusted at different times of the year, and might vary from one manufacturer to another. At some point during those 20 tanks, you probably went through some formulation change that you weren't aware of.

gfxdave99

ive been getting my gas at costco, its like 30-40 cents cheaper then surrounding stations for premium.. i get 93 for 2.10 this week.

TdotSSTSX

I use 94 from Sunoco. It ranges from 88- 94 cents CDN/litre. ($3.34 - $3.57 CDN/gallon).

gpsiir

"I suspect the real difference is in the formulation of the gas. The formulation will be adjusted at different times of the year, and might vary from one manufacturer to another. At some point during those 20 tanks, you probably went through some formulation change that you weren't aware of."

Thought of that, so I alternated tanks, e.g. first tank 91, next tank 89, next tank 91 (hey software engineer, so of course I'm anal retentive ). No, I really think the test conditions I used would have shown up a reformulation.... BTW, this test was done in the summer. In the winter, by law, all of the stations switch to this MTBE added gasoline that sucks in the worst way, I've already noticed my gas mileage drop about 1.5 mpg. It's worse in my toyota 4Runner.

VeniceBeachTSX

Interesting. All things being equal, 91 octane fuel shouldn't have much different energy than 89 octane. But I suspect things aren't equal. The two grades could be coming out of different refineries, have different forumulations, additives, etc.

As I've noted many times before here, alcohol is pretty high octane stuff, but has relatively low energy per volume. Kerosene (jet fuel) and diesel are very low octane -- actually aren't even measured on the octane scale -- but have pretty high energy per volume. And then there's the whole engine thing. The engine may develop optimal power with one octane level, while simultaneously being most efficient with a different octane. Read the fuel faq I posted and you'll see that this stuff gets pretty complex.

Wtbs2k

#94 from chevron

gpsiir

It's definitely odd. BTW, I feel pretty safe using the 89 octane, over at vtec.net, one of the engineers that worked on the TSX stated that the engine and oxygen sensor that the TSX uses will easily compensate for using 89 octane fuel, 'bout the only thing you would do is lose about 10-15 hp. There would be no damage to the engine. It would be very interesting for someone to dyno a TSX with the different grades of fuel..... I suppose that since so many things affect horsepower (altitude, air temperature, number of miles on the engine, etc.), it would have to be the same TSX on the same day..... Ah well, probably too much trouble.

JTso

iTrader: (2)

You can probably use 89 octance without any problems (just some power lost) if you stay within closed-loop mode and never run the engine pass approx. 5k rpm.

The oxegen sensor doesn't compensate for lower octance use. All it does is to monitor the air/fuel ratio (not octane grade) and feeds the info to the ECU. The ECU in turn uses it's internal programs (Short Term Fuel Trim & Long Term Fuel Trim) along with other sensors inputs to add or subtract fuel to the injectors by modifying the injector pulse width.

It is true that a richer A/F mixture can reduce the knocking problem from the quenching effect. However, the ECU is programmed to stay within 14.7:1 A/F ratio in closed-loop mode. This is where the knock sensor comes in. The knock sensor sends knock signals (if detected) to the ECU and the ECU retards ignition timing to compensate the knock condition. However, the stock knock sensor is only effective under certain rpm and only can retard a certain degrees of timing. Therefore, if you use low octane fuel and drive the car in WOT, don't count on the knock sensor or the O2 sensor to save your engine. Btw, if you hear the knocking, that means the ECU has reached the max degrees of timing it can retard, and it's where engine damage begins.

VeniceBeachTSX

At his altitude, he can most certainly use 89 octane quite safely at any setting. Peak cylinder pressure at 6000' is going to be 20% lower than at sea level to begin with and max power even at WOT is probably going to peak somewhere between 175 and 180hp in the best case.

High altitude, in effect, turns our engine into something with similar performance to a stock accord. The benefits of high compression are negated by the problem of low ambient air pressure.

As I said, a decade ago you couldn't even get 91 in many of the mountain states, and some gas stations out there still sell 90 as premium. At those levels, it's all you need.

JTso

iTrader: (2)

Good point.

kaikai114

do you really feel the difference in V power compared to other brands with same octane lvl??? I tried V power the other day, and felt a slight difference in smoothness when I went WOT

sauceman

I can't say I honestly did.

I don't really know why it should either. Maybe just a placebo effect. (Not meaning to offend you by any means)

kurt_bradley

The power gain is all in your head. Although, my fuel economy is definately higher (30 more miles per tank) on a regular basis. Not only that, but there is a lot of info out there that shows that the gas actually helps your car run cleaner than other premium fuels.

CraZydudE

is it ok if you fill half of the tank with 93 and the other half with 89??

MrChad

Yes assuming your are good enough to get an exact ratio 50/50 correct every time you manually make 91 octane....I've used the same methond to cut down 100oct race gas since it cost so much and I didn't need the full rating.

But really, does the 10cents make a difference, it's a $27k car, is the extra price for premium that big a deal?

I'd rather put premium in the fuel sipper TSX then pay to put regular in a 'Schlade or something.

But if you always put 93 in the tank and you are adding a half tank or less to top it off before a trip you should be fine adding 89, I don't think the TSX can make full use beyond 91 in any case.

ImportsRhot

I always use 93.....i thought we were supposed to use premium in our car. We only have 89, 91, and 93 here in florida.

MrChad

No, the TSX needs 91 or above but I think C&D did a test once and Honda's make optimum power at the minimum rec. octane rating. If we had 91 at the pump in my area I'd only run 91. We only have 87, 89, 93 in my area.

novatsx

Exactly, the rule of thought is no-pinging its fine. The only time you will get damages is from pinging (pre-ignition) Hell I ran 87 in my Z06 with no issues. Still ran 12'50s stock

LB-TSX

i've used 87 for over a year now. been getting great gas mileage, no knocking, everything seems to work just fine.

tehCOW

if you have enough money to purchase the tsx, then you should have enough money to purchase the premium fuel associated with this vehicle

MrChad

Amen! -- Why you wouldn't want the full 200hp per fill up is beyond me.

Besides the difference between 87 and 93 in my area; per avg. fill up....
...is about 3 bucks per fill up. It's a 3 dollar difference per fill up, that's insanely cheap.

All this from a 4cyl car that gets 26-ish MPG...imagine paying 50 bucks per tank to fill up an SUV that gets 12-15mpg.

Jeeture

I have new TSX. Dealer tells all their customers to use mid-grade which is 89 octane in California. Anybody try this octane for long time with good or bad results?

ariawoman

I've only had my TSX for a little over a month, however I have 3000 miles on it already. I've used 89 the entire time, and have been averaging 30mpg. (mostly highway driving I can get up to 31-32, mostly city i get about 28-29). I've not noticed any problems as of yet, but I am also not a "performance" driver. I don't think i've even had cause for the car to go above 3500rpm yet...

True, what people say, the difference is cost is pretty neglegable, however, since I'm filling up 2 cars, and do drive a lot, I decided to go with the middle, for now. The civic still only gets 87. I think it's jealous of the TSX....

Jennifer

Fibonacci

I still suffer from occasional pinging when I use BP/Amoco ultimate 93 octane. Very strange.

nbagadio

I've been using 87 octane in my 95 Integra GSR for awhile with no ill effects. I once say an article in the Acura magazine with some asking if it was ok to run 87 in an Acura premium gas car. Acura Magazine's respone: It's ok. You'll miss anywhere from 10 to 17% hp. That's what I remember...

MSZ

...Why buy an Acura if you can't even afford permium gas?

nitehawktsx67

i use 93 then add octane booster and i can honestly say the booster acually helps power some and gas milage