csj0952

Besides Sunoco, there is no gas vendor up here in the north east that offers 91 octane. Can I mix some 93 and 89 together? Will this be a problem for the computer if somehow I ended up not getting it 50/50 exact and the actual mixture ended up being 90 octane or 92?

Sorry if this is a stupid question. Just making sure....

Also, is there any disadvantage to putting in straight 93 besides the price?

Thanks,
Chris

cmschmie

Don't worry about it. 93 is just fine, if not better than, 91

I also don't think that mixing the two will get you 91

csj0952

so there's an advantage to putting in 93 over 91? Gas milage improves and engine performance? Or is it negligable?

Based on previous threads regarding putting in 89, I've heard it isn't recommended and small solids could be building up in your tank.

cmschmie

Sorry, edited it after you posted. I would have to guess, that there is a negligible difference, but would say that the negligible difference would be in favor of the 93

jlukja

I was under the impression that it would.

<-- not an expert

jwood_06TSX

I'm kinda with you jlukja, why wouldn't it mix? It may not mix compeltely even throughout due to possible viscosity differences, but i think it would prob be good enough. However, you would pay once for 89, and then again seperately for 93?.....does't sound all that efficient! If you wanted to do that i would just go with the straight 93 because if you would figure out the cost savings, it wouldn't be all that much for the year if you are planning on splitting the tanks of gas.

TheDukeZip

I would think if you did half and half at the same time this would work out to about 91.

The problem would be if you did what my dealer suggested which is fill it up when you have half a tank, and every other time do 89 or 93. Although at first this seems like it would work, it won't.

Say you start with a full tank of 93. When you're half empty, you now have half a tank of 93. So you fill the other half with 89. Assuming it fully mixes, you now have a full tank of 91. Wait until that is half empty, and fill up with 93. Assuming this fully mixes, now you have a full tank of 92. Next time you do a half fill up, you put in 89 again. Only this time, you are combining half 92 with half 89, giving you 90.5 And this is still assuming everything mixes together completely. Next time you'll have 91.75, followed by 90.375. So basically every half tank, your octane is changing, which probably isn't going to help out the ECU with fuel computations. Not to mention that you're not always above 91 octane.

csj0952

So the moral of the story is to put 91 in, if you can't put in 93.

TSX2345

Be happy that you get 93, some of us do not

n1ke5h

the other way around...

jwhite4

I used to do this with my old '85 Supra. Had a knocking problem on straight 87 octane. It was usually 10c/gal more for 89, and 20c/gal for 93, so I figured a 50/50 mix would cost me about 10c/gal more, but yield ~91 vs 89 octane.

At self-serve pumps, it's pretty easy (especially w/ a credit card - swipe one, do 87, swipe again, due 93). I work in NJ, I think at some point I might have said, "Give me $7 of premium (when that might have gotten me 5gal!), and then fill the rest with regular). For those of us (like me back then) that have more time than money, it was a way to save money compared to a full tank of 93. That was also when 10c/gal difference was a lot when gas was $1.20-$1.50 gal. Now at $2.25, and last summer (post-Katrina) at almost $3.50/gal, it's not a big deal.

Someone mentioned it maybe not mixing because of being a different viscosity. I have no sure knowledge of this, but I'd be very surprised if there was much difference. There's too much commonness in gas (distribution lines, gas pump, fuel pump and lines in car, etc). I'd think to have any significant differences.

Jeff

JayRoam

As far as I know, most gas stations have 2 tanks. Premium (91-93) and regular (87-88). The mid-grade (89-90) pump actually draws from both tanks, effectively mixing premium and regular into mid-grade.

rx280

Like jwhite4, I actually mixed 89 and 93, figuring that I was creating 91, pretty religiously for more than a year (with the TSX). My technique was the one TheDukeZip described. I'd let the tank get down to about half-full and fill up with 93, then, the next time the tank got down to about half-full, I'd fill up with 89, and so on. I’m pretty sure the gas in the tank was always between 90 and 92 octane. TheDukeZip is right: it couldn't have always been at precisely 91, but I doubt that was a problem for the ECU.
I’m no petroleum engineer, but I’m reasonably confident that the blending concept is valid. It doesn’t seem all that many years ago – though maybe it actually is – that you could get at least a half-dozen grades of gas at Sunoco stations, which had pumps with a dial: you’d turn the pointer to the desired octane number before fueling. I very much doubt that each station had a half-dozen tanks in the ground; the pump must have been blending gas from a couple of tanks to produce the desired octane. (I think Sunoco actually may have touted its “custom-blend pumps.”) And as JayRoam said, 89 is almost certainly an at-the-station mixing of 87 and 93.
Here’s why I stopped using my own blending technique. Because I was always driving with at least a half a tank of gas in the car, I was paying a weight penalty that probably negated the minor savings I achieved by buying 89 every other fill-up. My MPG calculations pretty much confirmed that. Another big plus was only having to buy gas half as often. My local Sunoco station – and Sunoco IS the only gas company offering 91 in these parts – helped out by lowering its prices by 6 cents a gallon one or two days a week, so I try to fill up on those discount days. (The thing is, you’re thinking: “Hey, great, I’m getting 6 cents off per gallon,” then, after putting 14 gallons in the car, you realize that you just saved a whopping 84 cents.)

iforyou

iTrader: (1)

It really depends on what the manual recommends you. If I remember correctly, 91 is the recommended one. If you put in 93, it won't damage or increase the performance of your engine, it will only hurt your wallet.

The reason that you need premium fuel is because of the high compression ratio (CR) in your engine. A high CR means that the pressure inside each cylinder chamber is higher and thus the temperature is higher too. The high temperature might cause premmature explosions to happen. These explosions are what we call knocking. With higher octane fuel, knocking will less likely to happen because the octane increases the temperature at which explosions would occur. And that's the only thing about premium fuel, all you are paying for is to prevent the knocking from happening. In reality, occasionally knocking is ok, it won't really hurt your engine. But if it happens often, then your engine will not last very long.

So if the octane is high enough to prevent knocking, then you are fine, you don't need to get anything higher. Cars nowadays are equipped with advanced knock systems that can determine the octane of the fuel. They can lower the CR automatically so that knocking won't occur even if you put in regular grade fuel. Of course, lowering the CR means decreasing your engine performance (not sure about fuel economy though, I want to know about that too), but I'm certain that it won't hurt your engine. And usually, that loss of power is around 5-10%, so you won't really notice it unless you are driving hard or going uphill.

Recently, I read an article (someone here posted the link to the site) about octane. And it shows that many auto makers (including BMW, Mercedes, Audi, Nissan, Honda, etc) agree that most of the time, premium gas is not necessary in their cars even if they recommend it.

I drive a 2nd gen TL-S and I put in 91 octane gas for my car. Even though I know regular grade won't hurt, I just want to put something better into the gas tank. But sometimes (a few times in a year) I do put in 89 because the price is way too high. In the end, it's really up to you, whether you want that extra performance or not.

DuckDodgers

Octane has no "direct" impact on gas mileage or performance, octane is simply a measure of the resistance of the fuel to pre-detenation/knocking. Now, given that fact, the use of a lower than recommended octane will impact performance because the engine's sensors will retart the ignition (and thereby reduce the power production) to try to keep the pistons and rods from punching out the side of the block or having their tops destroyed. So the engine computer is doing the dirty work, not the octane.

Having said that, some cars will actually run worse on higher than recommended octane fuel (example; in Car and Driver a few years ago, an Accord (recommended 87 octane) was run on a dyno with 87 and 91 octane fuel and made less power with the higher octane/price fuel...in the same test a V-6 Mustang (recommended 87 octane too) actually made a little bit more power on the 91 octane fuel).

fsttyms1

Just use 93

tlbkcal

how do you think they make 89? the tankers pump in 87 and 91. i use to work for the air quality district and permitted diesel engines so i had some training in gasolines and such

dolparism

91 and 93 won't make any difference.... but i won't go below 91.... but here we've got only 93...so i put 93....

ChrismanTSX

the ECU does not lower the CR but retards the ignition in order to prevent the engine from running as hot as it normally would. Running the engine as hot as it normally does causes low octane gas to detonate on compression/heat, before the piston reaches the highest point of its run, causing extra pressure on the crank, conn rods and valvetrain. this is why the ECU retards the ignition in order to protect the engine internals.

The dealership and my mechanic both told me that the ECU will protect the engine, so you could really run in on 87 octane. However, your fuel economy will not be as good, and you will get the full power rating, as the engine requires optimal ignition timing to generate its full power. It can't do that on 87 because of the knocking...

Trackruner228

iTrader: (1)

Here all we have is 87, 89, and 93. I have never seen 91 in NC so I always put in 93 just because they dont offer 91.

jwood_06TSX

So my buddy works for Sunoco (he is a Petroleum Distribution Engineer...aka he pumps gas....lol) and he told me that they only have 2 main tanks of 87 and 91 and they just mix the others for the 89 and then a different tank for the Ultra 93. They claim that their 93 is a much better mix but he said it is a little bit better but not going to make that much of a difference.

So i think the bottom line is, if you can 93 and its not much more in $$ than the 91, you may as well use the 93. If you want to mix the 93 and the 87, he said he does get requests to mix them occasionally (even though they have 91). Some people are weird....lol

Brandon24pdx

No, just run the 93.

CJams

Thats what i'm saying. Whats the difference in price? Like a dollar? It's worth a buck to not have to stop half way and start the other pump. And it's better for your car.

studville

Kinda offtopic, but I thought I'd post it here.

At my local gas station, they charge the same price for 87 & 89. The manager told me they did this because it cost them the exact same price to obtain. It didn't help me though -- 91 was still 20 cents more.

cmschmie

I had no clue that they mixed them to get a certain octane at the pump. Seems weird.

iforyou

iTrader: (1)

Thanks for correcting my mistake. I must've been thinking about the Saab's variable compression ratio system which is still in development.

So my fuel economy will worsen if I use lower octane for my car, but it will still get the full power rating? Or do you mean NOT get the full power rating? Cause with lower octane, the igition timing is changed (not optimal), and like you've said, you need optimal timing to make its full power.

Michael05

Gasoline is a commodity...it's all going through the same network of pipelines across the country, so there's really no difference in the gas itself between BP's 87 octane and Shell's 87 octane. BP might put 10,000 barrels of 87 octane into the start of the pipeline at the Gulf of Mexico and then they take out 10,000 barrels in New York or wherever...but it's not the same exact gas they put in (since it takes several days at least for the gas to travel through the system). They just take out an amount equal to the amount they put in. It's all mixed together.

The only difference between BP's gas and Shell's gas (or anyone else's) is the small % of additives they put into the gas at the end of the process, before they distribute it to stations. There might be some additives that might improve performance by a tiny fraction of a percent, or keep your engine a tiny fraction of a percent cleaner. I'm no petroleum expert though...so I can't tell you if the additives really do a whole lot.

But I'm guessing most of it is marketing hype. Price is the last refuge of a marketer...they need a way to differentiate their product other than price.

ChrismanTSX

yup, my bad. Meant to say that "you will not get the full power rating". For me, getting cheaper gas normally means worse fuel economy and less power, so I always put 91 or better, unless it's not available!

frescagod

you guys bought a $28,000 car and you're pinching pennies when it comes to the gasoline that you're feeding it. don't you find this to be a bit perplexing? your question stems from an action that would save you like $2 on a fill up ($0.10/gal for 17 gallons, so i rounded up). honestly, just put in 93 or 91, whatever. saving a few pennies and wasting your time by putting in 8 gallons of 93 and 8 gallons of 89 just to get a supposed "mix" of 91 octane is COMPLETELY INSANE. STOP BEING RETARDED.

sorry, i'm done.

iforyou

iTrader: (1)

Yea, me too. So even if something goes wrong in the engine, I know that it's not the fuel problem, and so I won't regret for anything

subdued

Chris (OP), I asked a related question a while back

https://acurazine.com/forums/showthread.php?t=33105

math formula included--if you care.

Ellas9

89 is in theory a mixture of 91 and 87 - they only bring trucks with 2 tanks to fuel stations. Assuming they mix it properly (i.e when they put in the station's tank or if the machine does it prior to it entering your car) then many have said, and I agree, that 89 will deliver better fuel economy because of the only moderately high compression ratio with the more energy rich fuel. Performance and efficiency levels will be optimized at the same fuel octane level - no loss will occur. The higher the octane, I think, you will lose efficiency and since your engine is not running at full efficiency, you will lose performance. The car asks for 91 so, just give it 91 - how cares if you miss the 91 on a given tank. Its one tank - and I don't trust the gas stations anyways...half the time, they probably don't give us what we pay for.

tits legendary

So if the only difference is the additives...Who has the best additives? I have heard that Chevron is supposed to have the best gas but is that true?

Michael05

Again, just an amateur opinion here...but I don't think 99.99% of the car owners out there could ever notice a difference. And if you could, it'd be a small, small difference.

There will always be people who swear by one brand of gasoline...just like there are people who swear by any other kind of product. And you'll occasionally hear the horror stories: "I filled up at [insert station name here] and got a bad tank of gas, so their gas must be lower quality...so I'm not going back." Nonsense. You can get a bad tank of gas at any brand station.

Personally, I choose my gas stations by convenience. Who doesn't have long lines or crowded stations? Which ones are easiest to get in and out of? Who doesn't have their credit card readers down frequently? If a station has a reasonable price and good access, then I'll go there.


I love making fun of people who talk about how they saved $.05 per gallon by driving across town.

Do the math. The cost to operate a TSX according to Edmund's is somewhere around $.50 per mile. Subtract gas from that equation (roughly 15% in year 1 of ownership...slightly less in later years) and you have a cost to operate of about $.43 per mile. Drive 5 miles out of your way and you've just spent $2.15. Assuming you put 15 gallons into your car, you have to be able to save about $.15 per gallon just to break even. And that isn't even taking into account the cost of your time. Personally, I know I have better things to do!

It's almost never worth the drive. And it isn't worth agonizing over. You can better use your time doing something else that'll save a whole lot more money (clipping coupons from your Sunday newspaper, etc.).

I'm not saying if there's a gas station down the road a mile and their price is $.20 a gallon cheaper, I wouln't go there. I might, assuming it isn't a big hassle (see above). But most of the time, trying to save a few cents per gallon is a losing proposition.

DuckDodgers

Chevron's "Techron" is the additive of choice if you are slopping something into the tank every 500 or so miles to clean up the injectors. (Consumer Reports from some years ago...but I've seen more recent stories indicating the situation remains the same)

I'll note that all major companies use more additives in their 91 or 93 octane gas than in their 87 and 89 octane. I've never added a fuel system cleaner to a car I've owned that uses premium octane...those that 've owned that use regular or mid-grade, I slap a dose of Techron into the tank every 5000 miles. In both cases, I've never had injector problems ...no proof, just my experience .

ChrismanTSX

So many threads on gas...

check out www.toptiergas.com to find out who has the best gas in the country.... won't save you from the odd tankful with some water in it, but will ensure that you minimze the odds of deposits, or clogged injectors.

Michael05

Sounds like an interesting concept.

But I'm trying to figure out why I haven't heard about this before. I don't remember seeing anything like this in my manual, but I have an '04 so it might be too new for that. Anyone else see this in their manual? Or in any other official communication from Honda/Acura?

I'd think if it was that important, that they'd put it into the manual as a recommendation. (Or maybe they've already started?)

synthetic

They've already started.

If you go to Acura's website they have a section about it.

What they have done is, they've gathered with top auto brands like Toyota, BMW, and some others to make sure they don't experience what Mercedes Benz had to go through.

Some rich dude in China kept putting very low-quality gas in his Benz and the car kept breaking down. He eventually got sick of it and destroyed the car in front of a camera using a big hammer. Then he sued Diamler(Mercedes) for time-lost and stress. He didn't get anything out of it, but launched a campaign against Mercedes and apparently hurt their sales in Hong-Kong big time.

Top-tier is an extra inspection step that some petrol companies have agreed to implement in order to make sure their mixers are less fault-tolerant and their delivery methods are more strict.

How effective this whole deal is, I don't know, but since I read about it, I have put nothing but SHELL gas in my car. Shell is the only company offering Top-Tier gas in Canada.

There are more in the US.

ChrismanTSX

...actually, Petro-Canada and Chevron also comply to the Top Tier gas requirements in

synthetic

That must be new. Up until a couple of months ago, Shell was the only one.

I don't like Petro-Canada as they are one of the major reasons behind gas-price fluctuations in Canada(ask their workers) and I have never seen a Chevron in Canada.