I just bought an 06 TSX 5AT and I am in LOVE with it.. The original owner took great care of it, all 80k highway miles, with no mechanical problems (except for slight rotor warp/vibrations but 75% pads? hrmm)..

Only concern is that the original owner admitted he has used regular 87 octane since he originally bought the car with no problems.. My question being, should I be concerned? Can I still benefit from using premium and “help” the car at this point?

 

Congrats! I still enjoy my 06 to this day, and I'm sure you'll enjoy your car for as long as I have.

You will still be able to benefit from using premium (your car will advance its timing to normal), although you might want to consider using a fuel system cleaner to clean out the system. I just tried BG 44k fuel system cleaner at http://www.handa-accessories.com/tsx04.html on my 06, but since I have always used premium, I haven't really noticed any change. You probably would notice something. It should clean out your fuel injectors, intake valves, and combustion chambers.

Also, it might be a good idea to take a moment to replace your spark plugs.

Be sure to use as much of the regular fuel as possible (empty tank) before switching to premium, otherwise your tank will be "diluted" for a couple of tanks.

 

I know many of the others will disagree. I am a rather conservative driver doing lots of highway driving. Our 06 tsx has been on 3 cross country roadtrips. I also drive from NC to NJ and back every few weeks. I have all the service done by a acura dealer (another rarity) which I feel does excellent work and does not overcharge. When I first owned the car I used premium gas for probably 6-7Kmiles (not just one tankfull) I switched over to regular to compare. Lets just say I am still using it. Had the spark plugs replaced at about 110K miles. If your car is running good at 80K miles using regular why change. Do you know if the power steering recall was done and also when was the last time the filters were changed. If you plan to be a high-spirited driver then maybe premium may or may not be better. Go to the benefits of premium gas websites and read what they say. Good luck and safe driving. Excellent cars-

 

Using premium fuel is mostly the decision of the driver. I had an 08 TSX and used premium 99% of the time. You will notice a little higher gas mileage using the 91 octane vs. a lower one. The fuel mixture burns better. I used mid-grade on a few occassions, but that was only to fill up from 1/2 tank.

 

Interesting point. Is the knock sensor the only thing that would cause the timing to be set back? ...and isn't knock much more likely to occur as rpm increases? Maybe someone with a light foot could "get away" with regular without too much consequence...

 

If you were to drive my tsx you would not have any idea I was using regular gas unless I told you. It has more than enough power for those times it is needed. I also get excellent gas mileage as I try not to race it.

 

Octane levels are a measurement of how easy the gas can ignite. The higher the octane level, the harder it is to ignite.

Now, imagine an engine driving down the road. The cylinder walls and pistons are hot from all the air/fuel explosions. If we think about one cycle, we see the fuel entering the cylinder. Next, we see the piston compressing the fuel. Any liquid or gas that is compressed becomes warmer. Coupled with the heat from the cylinders and pistons, the gas becomes pretty hot.

Now, here is where regular versus premium comes in. If the gas becomes too hot for regular, it can pre-ignite (pre-detonate) before the gas is fully compressed and the spark plug is ignited. The gas ignites as it is being compressed, and an uneven burn occurs. The piston is being slowed from the wave heading towards it. When the spark plug finally sparks, another end of the gas is ignited, and now you have two waves. The engine knocks/pings, the car detects it, and it retards the timing. The retarded timing causes the spark plug to wait until the piston is on its way back down, resulting in lost power and unburned fuel.

So, to answer your questions, the car uses the knock sensor to decide if it should retard or advance its timing. Knocking may be more likely as the rpm increases due to more heat, but it can occur at lower speeds. I had one car that would ping at idle.

You can get away with regular, but don't expect your engine's maximum performance and fuel economy. You will also spend more on regular (lower MPG means needing more gas to go the same distance), but that is something that should be left to the typical fuel question (since your thread is not the average fuel question). ;-)

 

Thanks guys for the answers, much appreciated! I'm really excited about this car..
@SoCaliTojan.. He did have the Power Steering H. done in Oct. 2010 with operation code "75ACZWPSH"?
Not sure about the spark plugs but I'm going to look in them..
How much better of gas mileage city/highway can you expect from premium 91 vs. regular?

 

I have kept exact records of my gas mileage, gas grade, and station used (among other things like $/L, $/km, etc) for the past 5.5 years.
I've used regular and mid-grade on many occasions and notice VERY LITTLE difference in mileage - probably about 0.25mpg less with regular vs premium (so about 1% worse mileage - the spreadsheet is at home but this is based upon my decent memory of looking at this before).
However, I ALWAYS note the fact that I can feel a fairly significant degredation in performance. Most notably is lower-end torque -- from a stop, or passing in 5th or 6th on the highway. With premium, the car runs perfectly. With regular, the car needs a downshift (or more patience) to go with gusto at low RPM's. I've never heard pinging/knock, but the knock sensor must detect it because the performance is noticeably different when running regular.

My $0.02: If you are a spirited driver, run premium. If you are a conservative driver who never passes anyone: run regular. If you want all 200HP from your high performing engine: run premium. If you don't mind less HP from your car, why didn't you buy an Accord.

 

Just the answer I was looking for thanks!

 

Ditto the recommendation on a cleaner and new plugs, Wes. I should think no other long-term damage was done, but you might want to take it to a dealer for routine checks. Verify that the prior owner did the 60,000 maintenance. Tranny fluid and brake fluid replacement might be a good idea if not done within 30,000 miles (or 12 months for the brake fluid). Also check if you the Power Steering Hose recall has been performed.

When you feel you've evacuated the regular fuel from the tank, and filled up with 91 octane or better, I would disconnect the battery (red, hot) terminal for 30 mins, to flush any memory out of the ECU. Make sure you have the radio code so you can reactivate it (it's hidden in the car, or a dealer can look it up for you with your VIN). You'll also need to reset the clock, naturally.

Since you have a 2006, consider getting the Hondata reflash. It's cheap, simple, and unlocks some hidden performance from the car.

 

If I bought a car with 80K on it already, I'd do everything the manufacturer recommended, including using the correct octane fuel.

If I didn't know the maintenance history, I'd take it in for a 75K service and get the other things done the others here recommended (or I'd get the 90K service done early). Then you know where you stand on the service.