Iridium plugs

The car should run on regular 87 octane fuel. It should not be necessary to use medium or high octane fuel.

If the engine doesn't ping, the octane is high enough.

A Corolla should barely ping, if at all, on 87 octane. Either the gas stations in your area are cheating, or something is wrong with the car, such as a vacuum leak.

The Corolla, or even the Camrys should be able to run on 87 gas without pinging. If the engine pings it usually means it's not as healthy as it should be (e.g., lean mixture condition, excessive carbon buildup in the combustion chamber, plugged fuel filter etc).

You already found the advantage of iridium plugs that it's thin center iridium alloy electrode allows for a lower firing voltage and the ability to ignite leaner mixtures (normal is about 14.7:1, the iridiums can ignite IIRC 17-18:1 lean mixtures). I know, these are great stuff.

The prices have come down a lot for these excellent plugs (~$12 -> ~ $6). For those who still have to save a couple of bucks over NGK Laser Iridiums or Iridium-IX, try Autolite Iridium XP with 5 years unlimited miles warranty. $4.99 after rebate at Schuck's or Kragen. However, it's said to have less Ir than NGK.

Select plugs only by using the application catalogs and not "cross reference charts":

NGK:

Autolite Iridium:

I was told by the dealer when we bought it, to use high octane and that we could alternate between that and medium octane.

Is there a reference for that?

I haven't read the manual in years but believe it said high octane.

But I can't change the mixture to lean it out anyway, can I?

Thanks. :)

See my response to your other post. Unfortunately, most dealer sales personnel are not very knowledgeable about the technical aspects of the products they sell. If you ask the service department, they are more likely to give the correct answer, which is 87.

You cannot change the mixture to lean it out, and there is no advantage to doing so because an engine that is leaner than it is designed to run will produce higher emissions, less power, and lower fuel economy.

No, the purpose is not for the owner to lean out the mixture. But that the plug is capable of operating lean of stoichiometric mixture.

As I mentioned, if the engine can't operate at stoichiometric, it's got a problem.

I wonder why it always got rougher running on medium test then?

If we went back to 91 octane it got better again.

Have you tried the old standby remedy for rough-running engines, a bottle of Techron to clean the combustion chambers, intake valves, and fuel injectors?

I've never heard of a Corolla being designed to require more than 87 pump octane, and even V-6 Camrys are specified for just medium 89.

Up here in Canada, my 99 Camry V6 runs just fine on REGULAR grade gas. The computer adjusts everything to compensate. A couple of tankfuls of Premium make NO perceivable difference in performance. Perhaps minor fuel economy improvements. Not worth the extra cost.

If it was running poorly on 87 octane, then something else was wrong, either something with the ignition system like spark plugs, coil, ignition wires, base ignition timing, or something else.

I don't know about that, but I use a can of BG44k after each oil change.

Jeez.

The dealership told us that when we bought it, and the manual said 91 too, we had no idea about this, all these years!

You shouldn't need fuel injector cleaner that often, and over-use of fuel injector cleaner can sometimes degrade flexible fuel lines. I have never used fuel injector cleaner in any of our vehicles and have never experienced a fuel injector problem. If you feel better about using fuel injector cleaner, once every 30,000 miles or so should be plenty.

I can attest to this. Overuse of fuel injector cleaner can turn around and clog/crack an injector and if you're in 'Lithia Dealership' territory, they'll spend 10-15 hours diagnosing it and then attempting to pass on $90/hr x 10-15 hours and $150+ for the injector....

I would strongly suggest NOT using injector cleaner often.

I would strongly suggest NOT using injector cleaner often.

But BG44K isn't "injector cleaner", is it?

Here's what they say about it. I'm not sure it's termed as "injector cleaner", per se.

BG 44K® Power Enhancer® BG 44K® Power Enhancer® safely, rapidly and thoroughly removes engine deposits in combustion chambers, intake manifolds, ports and on valves. It restores flow in fuel injectors and cleans the entire fuel system. BG 44K® Power Enhancer® improves fuel economy and reduces exhaust emissions. It restores that ?like new? driveability to an engine?s performance and keeps it running better, longer and more efficiently. Add one can or bottle to fuel tank at fill up. Catalytic converter and oxygen sensor safe. NOTE: After cleanup with BG 44K® Power Enhancer,® regular use of BG Supercharge®II, Part No. 202, in gasoline engines or BG Diesel Fuel Conditioner with DPL, Part No. 2276, in diesel engines will prevent deposits from forming in the fuel system and upper engine for maximum driveability and fuel economy. Part No. 208 Part No. 208A 11 oz. (325 mL) can