Regular Unleaded vs Premium

[matrixxrsman]

My apologies if this question has been asked a million times before but I have gotten conflicted information about my XRS that I purchased last week.

When I picked up my XRS my salesman told me that I only need to fill up with Premium gasoline once every couple of tanks but yet on the fuel door it clearly states "Premium Fuel Only"...Obviously Toyota knows what they are talking about when the placed that sticker there...but why would the salesman tell me something that goes against what Toyota recommends...should I stick with the Premium?

Thanks again for your help and opinions!

[silver04rollas]

Use premium only (atleast 91). It would be foolish to run regular gas on an 11:5:1 compression ratio car. Granted it will work for daily driving in city traffic, but it would cause excessive knocking and sluggishness. It will be dangerous getting into high revs due to premature detonation of lower octane gas in the cylinder.

[acrylucs]

You wont really hear or feel any knocking because the ECU will adjust itself. thats a bad thing. It will limit the engine to avoid knocking and i've heard the way to correct it is to put back only premium and reset the ECU by unplugging the battery.

[ksbrace]

I agree with the other responses. Higher compression engines like the 2ZZ require higher octane to prevent pre-ignition. On regular fuel, the engine will automatically make adjustments to prevent knocking, and those adjustments (retard timing, richer mixture) will decrease fuel economy, perhaps to the point that you might not even save any money by buying regular! As a single data point, a friend with a high compression Volvo (and a long commute) did experiments and determined that his fuel costs were nearly identical on regular and premium.
Of course, none of this is true for the 1ZZ engine. It is designed for regular, and higher octane fuel is a waste of money for that engine.

[XRS yo]

Premium -- especially if you plan to make use of the Lift you paid extra for in your 2ZZ.

On the other hand, my gf's mom has an 05 (corolla) XRS and has used regular since day one -- but that car has barely been over 5k, so it hasnt had any problems.

But -- it costs like a 2 bucks extra to fill up with prem instead of regular. whoopie doo.

[D Rock]

Dealers often don't know what they are talking about. When I bought my Matrix, I found that I had learned more about it by researching it beforehand than the dealer knew. I tested him on a couple of things and he didn't do well. One of my checks what the fuel type on the XRS -- he told me it took regular.

Listen to Toyota, not the dealer.

D Rock

2005 Toyota Matrix XRS

[trdbryan]

Yeah if it says "premium only" you only put premium unless u want to take a big risk of damaging your engine. The cars that can run on both would say "premium recomended" that means that you will get the best performance with premium but it is not a must, "premium only" means "Premium only"

[nmehes]

use any kind of gas...as long as it is PREMIUM.

[matrixxrsman]

Thanks for all your help everyone...so because it accidently got one tank of regular...I should disconnect the battery to reset it?

[ksbrace]

It certainly won't cause any harm to let it adjust itself over time. If you were planning a day at the race track tomorrow you would want to reset it. Otherwise I wouldn't bother.