93 octain ??????

just a question. yesterday i stopped for fuel they had no regular(87) (89). so i put in a full tank of {93)didnt want to drive 50 miles to get (87) . i was on fumes. i noticed my exhaust note is much quieter and it seems sluggish is this normal for the 5.3 ? ive allready drove 350 miles sence and will fill up with (87) .

If you don't have any significant performance mods the 93 is a waste - I also suspect that your PCM had a mild coronary and tried to reset all of its tables for the frst 50 miles or so.

11H will join in shortly on this issue

Also, as TexAVfan pointed out some months ago...

TexAVfan said:

I have used both 87 and 89 octane seems either is good - do not use higher as it will cause predetenation (spark knock or clatter on acceleration) because of the higher cylinder temp. If you want to use higher octane you need a programmer and 180 degree thermostat to cool down cyl, temp.

Click to expand...

thanks guys for the info thats what i thought filled up with 87 this mornning back to normal . gas mileage was the same 18.4 again thanks for the come back

I want 18.4!!!!

I average about 16....

I seem to do a little better on the 89.... but because gas is a little higher here I stick with 87.

Hoping that mobil1 and new plugs and wires will help a little.

I'm really not too concerned about the milage... am always willing to accept a little improvement