Cylanth

With the 4 cylinder TSX, you have the option to use Regular or Premium fuel. According to the manual and to the gas cap, Premium is "recommended", but NOT required. A big distinction.

I always read that Premium fuel will give you better performance and mileage. I wanted to test this out for myself. I drove two weeks with both fuel types. Exact same route every day to work.

With Premium Fuel, I got 26.4 mpg. With Regular, I got 27.5 mpg.

Obviously, there may be some factors that I am not considering, but overall, I got BETTER mileage with Regular, with no real noticeable decrease in performance.

Since Premium is not required for this type of engine, I will probably just use Regular from now on.

Can anybody else validate or refute this data?

nj2pa2nc

My 06 6MT has 98,000+problem free miles using regular gas. Great gas mileage and good performance.

ESHBG

Oh no, not one of these threads again LOL

Sure! What was the air temp/weather for the full two weeks? What station did you use for the fueling? Did you manually calculate or rely on the computer? Was the tank COMPLETELY empty of Premium before you put in Regular, and then calculated? There are many factors that can come into play here...MANY. It would be very hard to do a 100% accurate test in the real world. It is definitely fun to do our own experiments, though, and I can concur w/ that.

Like I have said in many threads in the past, I will stick to 91+ and not run the risk of any knocking issues or decreased performance (no matter how little that may actually be).

HHCZ

I did this test with my other car, 2 litre 4-cyl, and I got the same results. On premium the mileage was worse, and I didn't feel any performance difference.

Many tests ended with the same results: premium fuel is doing something only in high-performance engines, like Mitsubishi EVO or Impreza STI.

ESHBG

Okay but what exactly is your "other car"? If it's an engine that is meant to run on 87, you may actually see the same or slightly worse mileage when running Premium, so nothing too shocking there.

frescagod

you can spend $30,000 on a car, but you won't spend $3 more per fillup (if you're filling up 15 gallons and 91/93 octane is $0.20 more per gallon than 87 octane)???

am i missing something here? what are the "other factors" that you're conveniently not considering here?

just curious.

princelybug

iTrader: (16)

Well, if it was me, I'd fill up with the "recommended" premium fuel.

Cylanth

Its not an economic issue. Obviously, if I only cared about gas mileage, I couldve bought a Prius. But it seems there isnt any real benefit from Premium with the 4 cylinder, and I am trying to verify this. I know with the V6 TSX, Premium is required, but its optional for the 4 cyl. With my previous car, the WRX, I definately noticed a difference in performance with premium.

I'll keep doing my own tests, but I have a feeling the 4 cylinder TSX engine is not optimized for premium, or there is such a small benefit its not even noticeable.

09TSXTech

Our engine K24Z3 has a relatively high compression ratio of 11.0:1, for that reason I feel better to use higher octane fuel to lessen the chance of engine detonation/knocking.

If there's no knocking/pinging issue with the regular gas you use, then by all means.

I know in some cars, use of premium fuel will result in a slight horsepower gain, as the engine electronic management system adjust the timing and other variables to take advantage of the higher octane, not sure if that's the case with our TSX.

katmai

I keep telling myself that all the time...why buy a 30k car and cheap out a few bucks on gas? Even though there's no discernible difference to me, I knew it took premium when I bought it! If you can't afford the premium gas, maybe you should have bought a different car! lol

It is recommended I guess, but why recommend it if there truly was no difference? Hyundai advertises their Genesis as able to take both regular and premium, and even publishes different numbers for each. I just put premium in mine. A few bucks isn't worth it when I spent 30k for the car. The engine is designed for premium. Otherwise I highly doubt they would recommend people spending the money for no reason.

Cylanth

Where in this thread did I complain about gas prices? I could have afforded a new Mercedes Benz, money is not the issue. My complaint is with the TSX 4 cylinder engine. It does not seem to be properly optimized for Premium gas, or it simply doesnt need it. And nobody has provided any data to refute this claim, only having blind faith in the manufacturer's recommendation, not requirement. By all means, keep using your premium. I know people who only drink bottled Evian water, and think its healthier for them.

Farage

quoted from acura.com:

Customers who choose to use Regular gasoline should expect reductions in power, performance and fuel economy.

those liars.

09TSXTech

This is from the 2009 TSX Owner's manual

Fuel Recommendation

Cylanth, I think that answer your question. Our car is designed to operate on premium unleaded gasoline with a pump octane number of 91 or higher. In general, it's best to follow manufacturer's recommendation. However, as I mentioned earlier, if you have no knocking/pinging issue while using regular gas, then by all means.

samwlee

To each their own - but last year at my Acura dealership, I was told by the Service manager that Acura sent out a notice that the 09 TSX no longer required Premium fuel. Just recommended... so up to you...

Farage

so why would they still post it in the manual and their website?

Farage

oh i misread your post. yes it is recommended, not required.

Cylanth

How does it answer my question? It only raises more questions.

I rather focus on this part: "Use of a gasoline with a pump octane number less than 87 can lead to engine damage." Fortunately for us, fuel with less than 87 octane is not even available. Therefore, according to the manual, Regular unleaded is perfectly okay to be used in the TSX.

It may say its "designed for optimal performance" with premium, but my own imperical data says otherwise. The TSX 4 cyl is not a sports car and not sports tuned for premium. You can beleive otherwise if you want to.

2009tsx6mt

Where do you see recomended vs. Required? I have been considering going back to Costco 87 octane. I went back and forth between 93 and 87 for several months a year ago. Got slightly better mileage with 87 by my own calculations. Probably about 7 fillups each. Performance may have been slightly better with premium. I decided to stick with 93 octane as I know my lawnmower, wave runner and ATV run much better with 93. Plus I am keeping this car to give to my 10 year old when he turns 16. I disagree with the poster about a 30k car and worrying about 3 dollars a fill up. Only paycheck-to-paycheck ie. the Working Poor think like that. I don't just waste money for needless things based off statements with no substance. Premium is generally 22-28 cents more per gallon. So it is closer to $4 a fillup or about $250 more per year.

ESHBG

Wow, a whole $250.00/yr. or $20.83/month. If you're really that worried about it, don't eat out once a month to make up for it and bingo, problem solved.

Look, I am all for not wasting money just for the sake of it but come on people, don't buy an Acura if you are going to be cheap.

Now for those who said that they actually got BETTER mileage on 87 that is interesting, and that I kind of/sort of want to try out for myself just to see. But I am certain that long-term it would do more harm than good and I want the best performance out of my car and the best care for its important parts so if that's 91+ for the long haul, so be it!

ttk5

is it just me or has this topic been covered like 5 times already

HeavyDuty

It *can* benefit from added performance with 92 or 93, or it *can* run on 87 or 89 for those who feel it's not prudent.

frescagod

well, it's a manufacturer's recommendation, so "blind faith" is a stretch. "blind faith" is belief in things like...Jesus, or things like virgin births. this is an engine, designed by engineers, and bound by the laws of physics and whatnot. it's one thing if the King James Bible says that this TSX should only run on 93 octane, but it's the manufacturer's guide that says you should use it. take that as you may.

as for the water comment, i'm pretty sure that Evian is healthier than the lead-infused, Prozac-laden tap water that we have in DC. if you disagree, come taste my water and get it analyzed. i'm sure you'll find high levels of lead, chlorine, and other chemicals that are left over even after the purification process.

as others have said, higher compression ratios = use higher octane gas, or you may have decreased engine performance and/or knocking, depending on the engine. go ahead and tell the honda engineers to kiss your ass and save yourself your $200/year. you may claim that it's not about money, but what is it about then?

katmai

I think its a fairly reasonable assumption as to why our cars recommend premium. Its certainly not blind faith! Gas mileage in itself is also not any kind of litmus test as to what kind of gas the engine was designed for. Better gas mileage has no bearing on whether you might be hurting your engine, reducing its life, or anything contrary to what the engineers had in mind.

My dealer put in regular gas when I bought the car...they also said its perfectly fine. Yeah, like I'm going to listen to the dealer...

I also put synthetic oil in my car even though Honda doesn't recommend anything other than regular oil. I even use a slightly different weight. Is that blind faith too? I also buy good quality wiper blades, window washer fluid, car wax, leather conditioners...I didn't buy the cheapest tint that was available, I had a clear bra put on to cover just about every forward facing surface...

..I have no inkling to skimp on ~$250 or more per year on my $30,000 car. I knew the costs before I got into this.

Thats just me. lol

I'm not refuting anything about gas mileage one way or another, but the motivation for the question is not exactly clear.

remudapro

I was told the compression is high enough it requires premium. With that being said. Rather be safe than sorry. I want my 20k investment to last as long as possible.

2009tsx6mt

Like I said earlier my other gas powered equipment runs MUCH better with Premium. I even had problems starting my ATV with regular. Moved to Premium and starts up immediately. At the time I was finishing up the testing on the TSX gas mielage and performance. Like I said slighlty better MPG with 87 octane. Car seems to run slightly smoother with Premium but could be in my head. Wanting to keep the car for long-time and hand to my 10 year old. Decided to use Premium just in case. Just starting to reconsider as $4 more a fillup is money tha I don't miss but then again I wouldn't take 4 dollar bills and throw out the window each week.

nj2pa2nc

as previously written by me-use what works for you-I saw no improvement when I used premium gas-yes I can afford it but why should I. I tried it for over 2 months which with my driving is 5,000+miles. How many miles do you average. I average 30,000 a year. My car is 100% stock-did not modify it- I also have no car payment and have all the service done by acura/honda dealers. I wanted a car with 6MT so the tsx was perfect for me. How long do you keep cars for. What happened to your 07 tsx?

katmai

Unless maybe you're leasing and you plan on giving the car back...then I wouldn't give a f%^@% LOL

TSteezyX

Regular is simply more prone to premature combustion in the cylinders which sends a message to the injectors to input more gas...naturally. Also, the engine has to work that much more/faster. So you use more fuel and cause unnecessary wear/tear on the engine. Might as well stick to Premium.

tsx671

This is the first nice car I've bought so I'm going to treat it right and just use the "recommended" premium.

Draconis77

I'll stick to the fuel cap label stating that the car requires premium gasoline. I plan on keeping my TSX for a very long time, so why take the risk of wearing it out faster? The car hasn't even been out for two years, so who's to say whether it makes a difference or not? Too soon to say imo.

nj2pa2nc

Proper maintenance and driving (highway vs. stop and go short distance) will help make your tsx last longer. I hope your tsx is a good as mine has been. I now have 98,000+problem free miles. I have all the service done by acura/honda dealers. I use regular gas.

Draconis77

Whatever makes you feel better about ignoring the manufacturer and saving $3.50 when you fill up.

coffeefingers

Beetlejuice rulez.

Oh...I'm sticking with premium for my TSX V6. Just to stay topical.

nj2pa2nc

It states not to use gas with lower than 87 octane but recommends 91 and higher octane. My car passed the 100,000 mile mark with no problems (knock-on-wood). I do not try to race it, drive it on high mountain roads or tow which is when premium gas should be used. When we were on one of our cross country trips one of the states had regular gas that was more expensive than premium. We still used regular so it is not about the cost. It is what works for us.

taperk600

my take on this..... our 2005 says premium is required and running lower octane may result in engine damage. The possible damage, I'm assuming, can be as minor as pinging & carbon deposits, etc...all the way to complete failure.....

Now our 2010 says 91 octane recommended.... with loss in performance possible. Well, it's my wife's car and she commutes 30 miles each way on the highway. I don't see where 91+ is going to enhance her driving experience. For those who run their cars harder...I'd say use of the premium would be best for performance results, not fuel economy.

Now, for those of you who don't understand what octane actually does for the combustion process, I would recommend some research on the subject. But basically it is the rating of the fuel to resist detonation in the combustion chamber as the engine burns the fuel. And it does that by cooling the burn...so a higher octane fuel burns cooler during the process where a lower octane fuel burns hotter. Hence, the reason why higher performance (IE higher compression) engines require higher octane to control the heat produced by the increased forces internally. Running a higher than necessary octane can actually decrease engine performance and fuel mileage as it cools the combustion chamber down too low for proper burn rates and inhibits the fuel from being totally burnt during that cycle. So, if you are running premium in your lawn mower and think it runs better or starts better..... I'd bet it's other factors such as the amount of ethanol in the fuel, etc. ..... but ethanol in our fuel is a whole other problem and discussion.

tsx_ridah10

I was reading the manual and it clearly states 91 or higher well in the Canadian manual at least. Why wouldn't you opt to at least 91 octane in your car? You just spent a ton money on the car - take care of it?

I would never put anything less than 91!!!

TSteezyX

That savings is negligible because he'll be back at the pump sooner than if he was using Premium.

Regular fuel---> Premature Combustion ---> More gas used ---> Engine working harder to compensate for premature combustion

2010RMT

Personally I use premium. The miles per dollar work out about the same and the vehicle is made for premium. Regular of course is ok in a pinch. MY 2010 TSX Tech has 1300 miles. When I tried one tank of regular the mileage dropped slightly.

I use Shell and their credit card provides a 5 percent discount credited to your next statement. No limit on monthly purchases.

nj2pa2nc

hope you enjoy your tsx as much as I do mine and you will get over 100,000 miles without problems, You can not really measure MPG on just one tank of gas. Mileage can change by the way you drive, traffic conditions, etc.

Tishkevich

iTrader: (3)

Meh like i said before, there is somewhere, on this forums the guy and a few others did the math of regular , premium and mid grade use over a year. Regular you end up spending $500 more money after 20k miles because of the lowered gas mileage and unefficiency of the engine.. and mid grade was like $200, and premium was actually the cheapest fuel to use in the long run.. Not to mention the 09's state its required so to me its required.

IMHO They put "recommended" on the gas tank in 10' because everyone was complaining that they HAD to pay for premium, and technically the car will run fine with regular in it, but you CAN and probably will cause long term damage to your vehicle.. not the engine blowing up or anything silly, but the engine working harder to compensate for the lower octane, leading to earlier worn out engine components.. maybe not 100k miles, but 200k miles? I promise.

The great thing about american's, we always want to go the cheapest route and enjoy the same things that those who spend more money do. In this situation, not many people consider the long term effect, and they do there own "self-diagnosis" of the issue at hand and feel that they're experience is more accurate then the professionals that tuned and created the equipment. Which of course is fine and dandy, but in reality if Acura had a deal with the gas stations to suck more money out of the consumer, you'd think they'd come out with a better product with a lot less issues.

Sure toyota's are an issue if you have an idiot behind the wheel driving, but acura's issue has your car in the shop for the first 6 months you own it before its up to par with the quality of the toyota in every other aspect.

Premium has a lot of added chemicals that keep your engine a cleaner then running regular as well, and for the extra 10 to 15 cents a gallon some times 20 cents a gallon if its 93 octane, How can you be so stingy for your vehicle?

You're saving a burger from mcdonalds every time you fill up at the pump, but if you counted how many times you fill up on regular and how many times you filled up on premium over the time span of a few months, you'd realize you're spending more money at the pump with regular cause the gas station attendant knows you by name, and knows exactly how much gas you need.