MaineMDX

I'm new to this site and in the market to purchase a TSX to replace my aging Accord. I've heard so many say that 91 octane is required. But, while browsing the Acura website under the heading of "Features", and I print out the features for any item it will also print out a few extra pages with 25 explanations.

19. Octane - RL, TL, RDX, MDX
Using gasoline with an octane lower than 91 octane may cause damage to the engine. Please consult owner's manual for details.

20. Octane - TSX
Gasoline with an octane rating lower than 91 may be used, with reduced performance. Use of a gasoline with a pump octane number less than 87 can lead to engine damage.

So from reading this I would assume that using 87 would cause no harm to the engine. I have been using 87 octane in my '01 MDX for the last 7 years with no ill effects. Highway mileage during the summer at 65 mph yields 25-27 mpg. I was told by Acura Corporate that 91 was only required while towing or driving with heavy loads and flooring it. I have plenty of normal power and never knocks.

This info is not normally viewable on the website, only if I print it out. Has anyone done a comparison as to if there is any mileage loss?

nj2pa2nc

I also use regular gas on my tsx-I am a conservative mostly highway driver. Get between 32-36MPG with no loss of performance or power after 70,000+miles. I say-use what works for you.

LukeaTron

The TSX has quite a bit of adjustability in the engine parameters (valve timing and lift on the intake and lift on the exhaust, ignition timing, injector mapping) so it has a wider margin of safety than most other cars with regards to the octane requirements. It will certainly take advantage of the extra octane rating if it's available (more power and a more snappy throttle response) but by the same token, if the ECU detects that the engine is knocking it can scale back how aggressively it attempts to run to point of actually reducing the compression ratio. You should be fine in terms of damage unless you're really beating on the car with 87 octane.

Over the long term however, any engine will benefit from the detergents added to premium gas. Even if you only run premium every so often, it does help clean out the top of the cylinder and the valves of carbon gunk.

march30th1988

Did not know that! I drive back and forth from UC Davis like every week filled up on 91! Maybe now I can use 87 and cruise control instead of using 91 and cruise control! =)

ESHBG

Hey I am as money conscious as they come but I have never understood buying a higher class vehicle yet running junky 87 in it. I want my engine to be in tip-top shape for years to come and I want to get the most out of it, so why not run what the manufacturer suggests?

I can personally attest to having a loaner that someone had put 87 in and getting worse MPG than when I refilled it with Premium. So...any savings you get when you fill w/ 87 could easily be lost during the course of the tank; it just doesn't seem worth it to me.

nj2pa2nc

depends on your driving habits-
Previously owned two cars-a 91 Mazda Mx-6 Gt and a 98 Eagle talon tsi-awd, both bought new. When we sold them the mazda had 250,000+ miles and the talon had 125,000+ miles. They both had the original turbo's, engines, transmission, clutches and ran excellent using regular gas. My tsx gets excellent gas mileage, has more than enough power using regular. I also have all the service done by the dealer. I tried using premium gas for two months. no improvement IMO. Oh yes premium gas was recommended for the previous cars. How did you actually know the loaner had regular gas-did you watch it getting it.

ESHBG

I watched the person return it as they said, "I was on E so I filled it, but with 87." [it was last summer and during the very high gas prices]. A few minutes later and after the cleaning, etc., voila, lo and behold that was our loaner then too. We ended up having the car for a week+ because the dealership ordered the wrong parts for warranty work.