I have the 2010 i4. Since it only recomends 91 octane, what is the "danger" of putting in 89 octane?

I drive 100 miles roundtrip daily so the difference in costs adds up.

Why is 91 recommended? I assume it's to maximize the horsepower and not specifically for durability or longevity of the engine. Since I'll be driving this car till at least 150K miles, I don't want to do anything that would reduce the longevity of the engine and other parts.

89 octane is usually the mid grade gas in NJ. The next level up is 93 octane.

Personally, I don't see why any manufacturer builds an engine that requires anything more than regular gas. I think it's all for psychological purposes...a car can't be a premium car if it takes regular gas.

 

I use 87 and the car runs perfectly fine.

When i first bought the car i was religiously using 91 but then i read on these forums that ppl are using 89 or 87 and they havent noticed any performance difference. Also, the Euro Accord does not require Premium and it has the same engine

 

I agree... even in the manual, it says the engine *may* knock if you use a lower octane gas. As long as it doesn't and you're happy with the car's performance, why spend more at the pump?

 

interesting discussion. Depending on how this thread goes I may try 87 out a few times too...my car IS a lease car anyways

 

I know you are talking about the 2nd generation of tsx. I am the proud owner of a 06. I tried using premium gas when I first bought it and then switched to 87 octane. Never went back to premium. My car now has almost 96,000 problem free miles and runs excellent

 

You only need 91 octane if you want your car to perform to its max potential.

I use 91 octane because I travel to around AZ, UT, CO, TX & NM with a lot of mountains, high altitudes, high heat, and long interstate runs at +85 mph. The last time I was in Colorado on I-70, I had the TSX in 3rd gear, with my wife and two kids and 200 lbs of luggage, going about 90mph, at about +10,500 feet above sea level and I was able to keep up with traffic (People haul some serious ass in Colorado!).

I don't think I could have done that on just 87 octane.

87 Octane is fine for normal commuter or flat interstate driving. The only purpose of high octane fuel is to prevent pre-detonation of the fuel in the cylinder because of the higher compression/heat of our 2.4L engines. Higher the octane level, the greater resistance to pre-detonation.

The euro 2.4L has a lower compression ratio and lower octane is needed (and it has less power also).

 

To clarify, I won't use regular (87 oct). I plan on using 89. I do understand the difference in "explosiveness" in the different octane ratings. As I said, my concern is longevity. My 94 Civic was sold with 176K and my 98 Accord (replaced with the TSX) was sold with 196k miles. I plan on having the TSX for at least 10 years ( single income but a 2 car family). 150K to 175K will be a min requirement for the TSX.

I'll give the 89 octane a try. Because I travel so far everyday, I don't gun the car (to preserve MPG's).

Thanks all.

 

My salesperson told me that regular was fine. I only had the car a month and have been using 93 untill now and have 1200 miles. I think I am gonna do the switch to 87 my next fill up since everyone here is using it and my salesperson told me its fine. My car is also a Lease so why not switch over to 87 to save a few bucks.. My CL would mis-fire everytime I used anything under 93 octane toward the end but it also had 170K miles..

 

my husband was stopped for speeding in Colorado-received a warning-Imagine if he were using a higher octane gas-car had a trunk full of luggage and other goodies with my husband and I. In Colorado and surrounding states they sell 85 octane gas and quite a few the highest octane was 89.
Used 87 and I think in one of the Dakota's regular gas cost more than premium-still bought regular

 

I have read somewhere on AZ that using lower octane fuel than recommended will result in a decrease in fuel mileage. Lower octane fuel will combust easier which means its more prone to pre-detonation (pinging). The ECU will sense this through the knock sensor and adjust fuel injector duty to add more fuel to prevent pinging. This will result in more fuel consumption and lower performance since the fuel mixture will on the fairly rich side.

Lower octane fuels will work and the sales people will recommend it since they don't want to scare away customers that prefer not to use premium fuel.

 

My gas mileage went down when I switched tiresnot because of the octane gas I was using-Was averaging 32-36 MPG. Went down to 29-34 with the new tires.

 

This past summer, Acura of Boston had a orientation for new and recent Acura owners. The Service Manager did a presentation, and one thing he mentioned was the Acura dropped the Premium fuel requirement for the 09 TSX, and said that it runs fine on Regular. There was about 50% of us who had 09 TSX and we asked several follow up questions about that.

Since then I've been running regular (87 oct) w/o issues or performance drop off.

 

Have you seen a drop off in gas milage with the 87?
I dont really mind a small decreese in performance (this is no race car) but would be bothered if I got worste gas milage cuz it would defeat the purpose!

 

That's 1 of my 2 concerns too. I also don't want to reduce the life of the engine or other engine related parts by making it work harder due to the lower octane.

A friend of mine has a 2nd gen TL and she said that she gets worse mpg's with non-premium gas.

 

I just don't see the purpose of buying a car of this caliber and running crappy gas in it. I'm all for being thrifty and not throwing money away but if one is too cheap and/or too concerned with putting in Premium, I would suggest looking at something down a rung or two (Accord, Altima, etc.). I bought this car for smoothness, performance, etc., etc., and I just can't believe that one will experience the exact same performance, MPG, etc., on 87 as they do with 91+ (and most times 92-93 is in my car).

I'm not going to play Russian Roulette with my engine and its sensors so I'll keep putting the Premium in 'er. I really think if you do the math on your MPG on 91+ vs. 87, you'd barely be coming out ahead...if at all.

 

guys just for curious, are US octane specs the same as in EU?
Here in EU we have at least 95 octane, to 98 octane as a "premium" petrol and even 100 octane as a "exclusive" petrol.

To be absolutely calm, our TSXs are pinging too

 

I don't own the car I am borrowing it for 30 months!

 

It's not about being cheap...it's about being sensible with your hard earned money. The question is a legitimate one. Acura only recommends using 91 octane. It doesn't require it. If I had bought the V6 which requires it, I would not even question the need to put in premium.

Also, I can't find a single gas station in NW New Jersey that sells 91 octane. They have 87, 89, and 93 (Sunoco has 94 too). So, does putting in 93 give you better performance than 91? If no, would 89 give you worse performance than 91?

 

Octane ratings in the US are calculated differently. For the same fuel, they are 4-5 pts lower than EU ratings:
http://en.wikipedia.org/wiki/Octane_rating

 

I understand your point, I really do, but they recommend it for a reason. And the fact that putting in anything less than 91 can create a knock in your engine (which is harmful) speaks volumes to me. This is not a normal 4 cyl as we all know, and it is tuned and tested for 91+. Why mess w/ the formula?!?

But I know where you are going with this, as 89 is higher than 87 of course and could be a good compromise; not as bad on the engine and may reduce your chance of knocking somewhat.

You are going to get the best, most accurate results if you try it and monitor it yourself. I say put 91-93 in for a full tank, run it as close to E as possible and record your calculations. Then put a full tank of 89 in, run as close to E as possible, calculate. The put ANOTHER tank of 89 in, run to E, calculate. I say put two tanks of 89 in because even a gallon or two of 91+ can skew the results somewhat, and you need a full, clean tank of 89.

This is the best time of year to do it too, because stations are now running the winter blends and that + the colder air = far lower MPGs. If your MPGs drop and your performance suffers, you will definitely feel it more now vs. in the warmer months.

 

I never noticed any change in mpg or performance when i switched over from 91 to 87

 

We have Mohawk/Husky gas stations in Metro Vancouver, their Regular Plus w/10% ethanol has 90 octane but sell at the same price as 87 from other regular gas stations. Their premium grade is rated at 94. I used both and have no issues with pinging in the past 18 months.

 

91+ because your car has 11.1 compression ratio. It will cause predetonation, but the car should be able to figure out that you are running lower grade gas and it will retard your timing like hell. You will lose performance and probably end up using a lot more gas. But you do it if you want to. Its not "Required" only "Recommended"

 

Neither did I-Then again it also depends on the way you drive-I did try using premium gas for over two month (not just one tankful) and then switched to 89 than 87 (no loss in power and actually nor MPG) My car now has almost 96,000 problem free miles. as other posted-use what works for you.

 

Where did you live in NJ? I live in NJ and work in PA (Center Valley). I almost bought my TSX at Lehigh Valley Acura (but they didn't have the one I wanted in stock).

NC must be nice this time of year.

 

So it sounds like knocking and lower mpg's may be the biggest concern. If the engine has to adjust for the lower grade gas by using more gas, would that lower the longevity of the engine and other related parts?

 

<---- I live in Bergan County NJ (Wallington) currently am going through a short sale on a townhouse in riverdale NJ at the grande on the corner of route 287 and route 23 by the walmart. I bought my Acura a Park Ave Acura , but used to always service at Wayne Acura cuz I used to work by there.

My next fill up will be 89 and will use that for a few fill ups before going to 87.. I am gonna let her down gently..

 

I grew up in Bergen County (New Milford and Demarest) moved to Sussex County (Montague) after I was married, then to Ocean County (Toms River) on to Warren County (Blairstown) then over to the Pa side-monroe county (East Stroudsburg) and now on the coast of NC between Wilmington and Jacksonville) I still try to get my car serviced at Lehigh Valley Acura (my brother lives in Allentown) My mom lives in Toms River so I am in the north often.

 

My in-laws are in Fair Lawn, Rutherford, and Paterson. I grew up in Keyport (Monmouth County) but now live in Hackettstown. I've been to Tom's River many times.

I've only had my car for ~4 weeks. I'll run premium for another 2 months (to let the car break in thoroughly and get a true mpg reading). I'll then switch to 89 and see how that goes. I won't switch to 87. I'll need to find the gas stations around that give the "x cents off on Y day" and fill up there once a week.

 

This is a very interesting information exchange.

Considering TSX 6M to replace HAV-6 6M after expiration of HCEW.

Appreciate hearing what sort of highway MPG y'all are calculating..........

 

Well my gas cap says premium required :-P So that's what goes in it 91 92 93 whatever the pumps got.

Just like the guy said up earlier, (i'll look for the thread ) this was discussed about 6 months ago, and a few guys did the math or pulled the math from a ratio website, and the gas mileage is not significantly different but over a span of 50,000 miles using 87 octane you actually end up spending a few hundred dollars more on gas then continuing to use 91 +. I mean 91 + is only 10 or 13 cents more expensive per gallon. Of course this was done at the gas prices at the time, etc.

I remember reading that post because thats what drove me to continue to use premium. Not to mention I'm a very aggressive driver, so the cleaning agents and the procurement of power from the 91 + octane will preserve and maintain the life of my engine rather then not having the cleaning agents and losing a few hp and that few hundred bucks after 50k miles :-P

 

In my area, there is a $.12 difference b/n 89 & 93 octane (we do not have 91) & that $1.68 difference seems worth it to me. I know there have been reports that you lose HP & MPG w/ a lower grade but I cannot confirm/deny those.

I will say, however, that in my old Accord I would occasionally put the 93 octane in & I could tell a difference in how smooth & responsive the engine was & that made me a believer that there was @ least a difference in the types of gas. Plus, I had always planned on keeping my 2004 TSX for a while so I wanted to use the Premium fuel just to ensure its reliability -- so far ~54,000 trouble free miles *knock on wood*

 

As the user of regular gas I can confirm it has more than enough power. As far as MPG's they did go down but not due to the octane of gas but switching the OEM michelin tires at 74,000 miles to Yoko's. I have all the service done by acura/honda dealers. I get complimented on how well maintained my car is. Not bad after 96,000+ trouble free miles (also knock-on-wood) I see you are from NC. I live on the coast between Wilmington and Jacksonville.

 

This is not a PERFORMANCE car so i don't understand what caliber you are talking about. I also don't understand when u say down a rung and mention Accord cuz I hate to break it to you but you are driving a Accord, and a 4 cylinder one at that!

 

What is more relevant is that the V6 Accord requires only regular unleaded while the V6 TSX (even though I have an i4) requires premium.

I have not read one single technical article that states why an engine can't be built and tuned to achieve X hp/torque rating and require only regular gas. Take that with a grain of salt because I am far, far, far from being knowledgeable about how engines work.

 

So you are saying this is not a performance-oriented car? You are saying that the same exact engine/specs in the 4 cyl Accord is also in my car?

You sound like exactly the type of person I was referring to and if you think they are the same car, than you should probably save your money and stick w/ an Accord.

 

I do not get good MPG when I use regular. I never get more then 27 MPG on the hwy (even when I use 93) and I don't have a very heavy foot.
High Octane has higher BTU's and gives you top performance and MPG but regular will not hurt the engine.

 

My mom owns a 08 Honda Accord V-6 which I drive when I visit her. She only drives it very short distances. Not good for a car. The accord 4-door does not offer 6MT which I want. The tsx has more goodies than even the v-6 accord. I prefer my tsx.

 

It's not the same engine BUT...if Honda can tune an engine to create similar performance with regular gas, then why does any manufacturer build an engine that requires premium? (keep in mind I'm not debating whether we should put regular, plus, or premium in the Acura)

Also, I did look at V6 Accord EX-L's. Would've been cheaper fully loaded with vs the TSX. I chose the TSX because:

1. Way nicer and more comfortable seats...my favorite part of the car
2. IPOD/USB flash drive integration
3. Longer base warranty
4. i4 at 200hp was more than enough power for me.
5. Car looked nicer

Also, here are the specs of both cars:
Accord i4 - 190hp at 7000 rpm's, 162lb ft @ 4400 rpm's
TSX i4 - 201hp @ 7000, 170 lb ft @4300

Performance is very similar as mentioned. My feeling is that manufacturers tune the engines to require premium when they don't have to. IMO, it's all about image...most people equate premium cars with premium gas.

For now, I'm going to stick with premium for a few months so the car is fully/properly broken in. I'll then switch to 89 octane to see if it makes a difference.

To be honest, I think going 10K (like the brochures suggest) before an oil change would be more damaging. The oil might be able to take it but can the filter? Same thing with transmission fluid changes (I have an Ody - notorious for trans issues - I change it every 15K).

 

In Europe, the TSX is the Accord so I agree with the above statement.

A performance car to me would be in the class of the Audi S line, BMW 335i/M's, and the V6 TSX/TL engines. I would not consider the i4 TSX (no matter how much I love it) a performance engine in today's terms.

With that said, just 10 years ago, V6's were only putting out 200hp so it's all relative to the current standards.