Ok, so I am asking this question in regards to my '00 celica GTS, but since the celica boards are useless, I figured someone here might be able to answer my questions.

The owner's manual recommends premium level gas. How necessary is that? Would it hurt the car to run on the middle grade? Would it be better to alternate middle grade and premium? Should I just run on premium and not worry about it?

I'm asking because I am getting rid of an explorer and was really looking forward to having my gas costs drop. I didn't think about the fact that the celica might run on higher grade gas, which will basically make the celica cost the same to gas as the explorer regardless of the better gas mileage.

I don't plan on running the car hard or tracking it or anything of that sort; I just bought a fun to drive daily car. I don't want to do anything that will hurt the car at all, but I also wouldn't mind saving a little extra money from gas purchases if possible. Can anyone shed some light on the subject? Thanks!

 

Since the GTS isn't Forced Induction I would say you can run it on a lower octane level, but you will suffer in terms of performance.

 

Munckee,

I won't get into the whole technical discussion, but here are some guidelines.

Basically, the higher octane level makes the fuel are bit harder to burn, aka stable. In engines of higher compression ratios, lower octane gas can ignite due to pressure or hotspots in the cylinders. That is what causes the 'knocking' or 'pinging' sounds. It's really something you want to avoid. Think of the pressures on the engine having a cylinder fire off timing.

So, all modern car manufacturers put sensors in the engine that 'listen' for early ignitions. If the sense them, they will retard the spark or take other measures to reduce it. That results in reduced performance.

To make a long story short, the idea is to use the octane rating closest to what the manual says. Most high-performance cars want 91 or better. In my area (DC), all I can get is 93 <insert myriad consipiracy theories here>. 93 is fine, and probably gives a bit more stability as the hot summer rolls in.

One of the car mags recently did a study and found what most people would have expected:

Higher grade gas in engines that didn't need it were not affected.

Lower grade gas in engines that wanted higher octane suffered from reduced performance.

So, it's best for your car to put in what the manual says. If you want to adjust higher or lower, listen for the knocking noise.

 

Is there any damage done to the engine other than lower performance? Is the knocking or pinging permanent, or if I wanted to use a lower octane (and hence lower performance) fuel for around town, would that be ok? Thanks for the help!!!

 

[QUOTE]Originally posted by munckee
[B]Is there any damage done to the engine other than lower performance?

 

No, its not THAT big of a deal at all. I'm just trying to understand the limits of the vehicle. If gas costs a little extra because I need to use premium, so be it. If, however, I had been told here that the recommendation was overboard, then I would have gone with a lower grade. As I said, I'm just trying to understand, not trying to cheap out.