SilverTSXinPA

Hello All. I have observed something about fuel economy with my 5AT non-navi TSX and was wondering if any of you knowledgable folks could offer an explanation. I recently drove from PA to florida. I have always used 92 or above octaine in my TSX and have always seen between 20-21 mpg city and around 29-30 mpg on the highway. I have about 7500 mi on the odo. I ran really low on fuel and pulled into the "Last chance Texaco" to fill up. To my horror..the Premium/Mid grade pump said..out of order. I put in a few gallons of regular (87 octain)...and headed back out on the highway. After a time that i thought the needle should have dropped...i noticed that i seemedto be getting better gas milage...AND...performance seemed really fine. So...being the fool hardy person I am..I filled the entire tank with regular...figuring one tank should not cause any harm. To my amazement...almost 34 mpg (70-80 mph)!!!...next tank in the flatlands of florida (93 octane) and right back to 20-21 city and 29-30 on the highway. Next tank..87 octane..and...milage back up to 33.5mpg....what gives? Any ideas?...Oh..and by the way...i could not feel a difference in performance...none...nada..nope. Sorry for the long post...but am i nuts? Anyone else try this?...I would love to know if there is a technical explanation. Thanks.

fdl

I don't have an explanation...only a guess. If you are using the computer to measure your mileage, which I am assuming you are, it has been shown to be inaccurate. Perhaps using different gas somehow amplifies this inacuracies or somehow confuses it. Again, just a guess but maybe you should try manually calculating your mileage and see what those numbers show.


Another guess, perhaps in "low octane mode" the engine...by runnign less agressively produces better gas mileage. Which would kinda make sense since there is a decrease in power (even though you say you dont feel it, the differnce could still be there).

slats

I agree with fdl. It may have something to do with running "less aggressively". And it would be wise to try calculating your mpg yourself. Just reset the odo when you fuel up again, and then divide the numbers between your next fillup by the gallons it takes. BTW, the TSX will run fine on regular, but because it can cause carbon deposits, if you use it all the time you will have to have your 1st tune-up done sooner. Hope this helps.

Slats

tinyau01

Could anyone explain this too?
My first tank when I drove it off the dealership last 510km until the low fuel lights up. Every tank afterwards last around 420km only.

DEVO

hmmm.. could be that in PA you had winterized fuel and in FL you got the good stuff.


Also, a lot of people are confused with octane... higher octane gas doesn't mean more powerful gas. It just means that it doesn't detonate as easily under compression.


In F1 there is no maximum allowed octane level but there is a minimum allowed octane level... why because you can get more energy out of lower octane gas (simple answer but you can find more on this on the net).

SilverTSXinPA

Thanks for the replies. I do not have navi..so this is all done manually. the less agressive setting due to the lower octane is what I was thinking too, but, so many have posted of noticable performance hits to not using premium fuel. I use premium as a rule because it is recommended by acura. BTW...lower octane fuel actual burns more completely than higher octain fuel, as octane is actually a combustion retardant so i do not see how additional carbon buildup would occur. It is interesting that the "seat of the pants" does not detect the performance drop. Anyhow...just wanted to share with everyone an observation. Oh..one otherthing..i thought about the winterized fuel...and i am getting the same results now that i am back in PA. Enjoy the ride guys...I sure do.

ryanc44

Maybe the dealership gave it that first fill with 87 or 89 (better mileage according to this thread) and I'm guessing you've been putting 91 or 92 in (not as good mileage according to this thread).

I've been recording my mileage since I've had the car (1500 miles on the odo)- might have to test this theory out...

ryanc44

What computer are you referring to? Is this part of the navigation system or is this another reason I should be reading the owner's manual? He mentioned in his initial post that he doesn't have navi, so I'm guessing he's calculating the good old fashioned way...

jonredraider

Not exactly on topic but the other day my fuel light came on for the first time. It was very close to 1/4 tank! Is that what everyone else is seeing?

fdl

navigation

TeigerSX

Yes, it has been discussed that the fuel warning light comes on RIDICULOUSLY early. I think with maybe 4 gallons or so left, so your "1/4 tank" guess is about right.

TEIGER

tinyau01

Do we really need premium fuel?

DEVO

The short answer is no, the correct answer is yes. The TSX is a very high compression engine which requires fuel (for performance) with a higher octane (91+).

Can you harm your engine using lower octane gas? Over time I would say yes. You should stick with the recommended octane level.

dom

What does Honda have to gain by telling you to use 91+ Octane?
Last I checked they don't have a vested intrest in the pertroleum industry.

The engine requires a higher Octane. I don't pretend to know why but I know it needs it. So if the engine needs it Honda wants to ensure you use it so the car lasts longer and performs as it should. The only thing they get out of telling us to use 91+ is to ensure your cars lasts so they look good.

If you really need that $200 to $250 dollars PER YEAR you save by using 87 Octane, then maybe you should have bought another car.

Stevestr

How DARE you try to bring logic to this thread!

People when you purchased your vehicles you saw clearly on the filler cap that it says PREMIUM FUEL ONLY. It didn't say optional or when you feel like it. What that means is that in an emergency situation, once or twice, you can use the 87 stuff and the car won't degrade noticably. It doesn't say 87 is recommended for daily drives.

Stop being so cheap with a $30K car and fill it with the recommended fuel. Besides, Honda may one day deny your claim for fuel system maintenance if they can prove your excessive deposits were caused by "improper fueling."

I'd assume anyone who spent $30K on a car would want the most performance out of it. Why skimp on the fuel, one of the lifeblood fluids of the car? I'm not rich myself but there are certain sacrifices I'm willing to make and premium fuel (and even Chevron on occasion which is a bank robber) is one of them.

Every time someone asks about fuel on here we have to have these heated octane wars.

SilverTSXinPA

Sorry for some of the confusion here. I am in no way advocating the use of an octane rating less than recommended. I discovered this fuel economy thing quite unintentionally as my original post states. Just found it curious that by using regular grade gas..the TSX (mine anyhow) seems to get the same gas mileage as the 4cyl Accord. It is also true that while Honda recommends 91 octane, in most areas of the US only 93 or above is availale. There is a downside to using "higher than recommended" octane gas as well as there is a potential for incomplete burn occuring in the cylinder leaving excessive depsosits. I read some time back about subaru owners feeding there 87 octane reqirement GT's Premium and having an increased incident of fouled plugs. So it is kinda goofy Honda/Acura recommending a fuel octane level not readily available in the target market area. Go figure. Anyhow, for the record. I regularly use premium grades of gasoline. Sleep better knowing that i am following the guidelines.

dom

tinyau01. I see your from Canada. Have a look at this thread if you hav'nt already.

http://www.acura-tsx.com/forums/show...&threadid=4255

Interesting because I apparently have no choice but to put in Sunoco 94 here in Toronto because its the only gas in Canada that does not contain MMT which according to Honda is harmful to the car as the manual states that we should not use gas containing MMT. (Have a look at the link above for more info)

But I'm wondering whats more harmful, using gas containing MMT or running on 94 Octane. And I fill up on the 94 religiously. Maybe I should drop down to 92 or 91 periodically?

DEVO

It has nothing to gain but Honda isn't stupid and realizes that the DUMB public associates higher octane gas as being BETTER. It is true that this engine needs a higher octane gas because of the compression but I'm sure the engineers at Honda could make an engine that uses lower octane gas with same performance.

"Luxury" car means... more expensive gas.

SilverTSXinPA

Thanks for the replies. One common misconception though about octane is that higher octane burns faster and more completely. Just the opposite is true, as octane is a combution retardant used to prevent preignition in the cyldinder (knock). As so many days passed with no reply here, i had a chance to do some research and talking with local mechanics. The concensus locally is that if the engine runs with no pinging, knocking, etc. then no damage of any sort is being done at all. In fact, an independent mechanic from a local Bravarian only shop said that it is actually better to run with the lowest octane that does not cause performance problems because the burn is more complete with lower octane fuels. He told me that he has seen that running higher than recommended octane can actually cause fouling of the plugs due to incomplete burning. So I wonder, as i cannot buy 91 octane where i live (only 93 and 94) is it better to run two higher and foul the plugs or two lower with no long term damage..only, according to acura, reduced performance?

DEVO

Try telling that to the people who insist on only using 94 octane for their cars even if the car is rated at 87. I always get a kick out of the ignorant.

dom

So then answer my question if you can. Which should I be using 91 Octance full of MMT which has apparently be proven to harm my engine. Or 94 which is the only gas I can use that does'nt contain MMT. We've been over this before so I think you know why I've been using 94.

And DEVO and SilverTSXinPA, I'm not sayimg I don't believe you guys about the high octane harming cars but how about some proof to back it up. Lets see some documented studies and reports.

SilverTSXinPA

I do not have the written proof you desire. I only have the word of mechanics im my local. There is a syndicated columnist (mike or Bob Sikorsky) who has covered this topic many times. I am sure you could either find the information on the web ir how to contact him. Hes column is called the Wheel Doctor or something like that. Since MMTs are listed as known to cause damage to your vehicle...do not use a gas that has them if you can avoid it. Simple enough? It used to be also that only Premium contained added detergent additives to clean the fuel system. This is also no longer the case.

Perhaps in my older age, I have become more cynical and i doubt that the actual octane listed on the pump is exactly what ends up in your tank. I think the TSX electronics are advanced enough to alllow for a very wide margin of error in the actual octane ratings without any causing damage or harm. In fact, the only warning (and it is not even a warning) mention in the manual for gasoline is that the TSX can use lower octane but with reduced performance. Nowhere does it make a mention of "occasional use only" or that "prolonged use will cause damage." These are also simply statements made here with no hard evidence or studies done.

dom

Indeed, Ford estimated that for every 80,000 kilometres travelled, one-quarter pound of manganese was deposited in the converter. These deposits are permanent and cannot be reversed by using a fuel that does not contain MMT.

General Motors chipped in, saying the spark plugs in some of its engines have a failure rate 50 times greater in Canada than in the northeastern U.S. Surprise, surprise, the only difference in operating conditions between here and there is the use of MMT.

I think I'll take chances with my Sunoco 94.

dirk

to answer domn's question: i was talking to my friend (and tsx owner) and he said that in europe the octane in the gas is much higher.. something to the effect of their lowest grade of octane is something like 91 or 92. since these cars are basically 'european' they require a higher grade of octane to perform to their maximum potential because that's what they were engineered for. i would think that if it says 91+ it's using 91 as the lowest reccomended octane and putting in higher grade's shouldn't have any kind of negative effects. but i'm no expert...

DEVO

I would go with the lower MMT (I agree with the research, either you put up or somebody else on this site did)... I wasn't using you as an example. I have seen people put in 94 in a 87 octane rated car.

DEVO

Domn, as for the reports... I have to look back at my car mags... I have read many articles on this. Also, a search on the net will show you the same.

dom

So you would rather put in 91 Octane that contains MMT rather than 94 Octane that does not?

And like Dirk said, the manual states 91 or higher and are'nt most premiums in Japan and Europe 94 at the lowest? or at least I think they are in Japan. So that would tell me that the TSX was designed for 94 octane or at least works best on the higher Octane.

DEVO

Domn... go with the one without MMT. When I said lower... I meant if you can find gas without MMT then I would do that. Let's say you find a 97 or 107 rated octane gas... no MMT as well.. I would go with the lowest octane rated gas with no MMT. In this case it would be Sunoco 94.

BTW... I use 93 because that is what we get around here. Has to do with sea level altitude.

TriniTuner

I actually wanted to test how many gallons were in the tank after the fuel light comes on... I went about 40 miles at about 17mpg when I ran it out of gas ... yes very embarassing. It took about 16 gallons to fill up after.

My average mpg figures are in the 19-21 range during normal city driving.

gogozy

the way Europe calculate the octan is different to NA, their 91 is like our 87..

gogozy

the only pump in GTA that is guarantee contain no-mmt is Suncoc 94, another research show not all pump use MMT "all the time" and higher the octane the higher contain of MMT, that means someday the pump may not contain MMT but someday is has, but lower octane fuel has less possibility of containing MMT. tha is my assumption.