So, my car gets really bad MPG when I use 93 opposed to 87. I do have a cel for a bad o2 sensor(replacing when tax check gets here). But has any one else had this problem. It does run better using premium but it just dont get the MPG. 94 LS auto 154,xxx.

EDIT: for got to mention I try to stick to Mobil gas.

 

why are you running 93 in a ls? if im not mistaken, an ls will run fun on 87, and it's not marked to run premium.

 

Why not take a little bit better care of my motor. 93 burns cleaner

 

i thought an ls ran better on 87 that's why it was recomended. if you wanted to take good care of your motor why wouldn't you use the recomended fuel? you said it your self, you got less mpg.

a bad o2 sensor will make for less mpg also. If you want to run on 93 you should have a tune up done with 93 in the tank, i think you might need a different gap on the plugs and timing adjusted. as i stated it most likely is tuned to run on 87 from the factory. not that any of this is going to make a huge difference. hope some of this helped

 

Yeah dude. 87 should be fine. Stick to that and save money on gas and get better gas mileage.

I've had a bad O2 before and after replacing it I did notice better gas mileage.

 

Actually, 87 burns cleaner. Smog test the same car on both, you'll find lower HC counts with regular.

Premium frequently includes detergents not found in the lower grades of gas though. Premium is still not worth it though, since you can just dump a bottle of injector cleaner in the tank once a year.

 

your car is tuned for 87, dont use anything else. it is a waste of money.
i had a 88 civic, i used 91 and the car got worst gas mileage and ran the same.
if youre using 91 and up for cleaning purposes, run bottle of chevron fuel cleaner every 3-5k miles.

 

i really dont understand the whole "run 93 to keep things cleaner" idea. Ive never seen a difference, 93 just has more octane to resist preignition.

 

The higher the octane, the SLOWER the fuel burns. This is good for higher compression engines with 10 : 1 or higher CR (like B18C1) since the higher compression will tend to detonate lower octane fuel at the wrong time. A lower compression engine like a B18B will burn 87 octane fuel easier. Running 93 octane may very well leave more unburnt fuel, causing a MPG hit.

I can attest that a new O2 sensor should make a LARGE improvement.

 

i have noticed the same problem...my previous DA had 200k on it and still got alot better mpg on 87... my DC2 gets shitty gas mileage now with 93. I just replaced fuel filter, pcv valve, fuel injection clean, new intake filter, spark plugs and wires...Im gettin close to 300 where my 92 DA got 300+ with 200k miles...i dont understand...

 

Um, a B18C will never get the mileage of a B18.

My 212k mile 1991 LS managed 26/32 city/highway without issue.
My 76k mile 2000 GSR gets 20/26 city/highway...

Er, Los Angeles driving, so my city mileage is always lower than most people, due to idling at lights and such. I literally have a 35 minute 6.7 mile commute.

 

that is NOT true.

 

x2

 

wrong my DB8 has gotten as high as 37mpg and as low as 24mpg
i average 30-31 on almost every tank of guess

troof

 

This is spot on. Thinking that running higher octane fuels will give you more power is a common misconception. Running 93 in in an engine tuned for 87 will result in a slower burn which will result in worse MPG, higher emissions, and reduced power. You can run 93, but get it tuned for 93. Do that, and you'll extract some power out of the engine

 

when you reset the ecu it will reprogram itself for the fuel you run (somewhat) if you go from 87 to 93 octane, try resetting the computer and see if you get better results

 

Does running 91 in a LS make a difference?

 

did you even read posts before yours?

 

yeah ive noticed the same thing with my 99 gsr.. i have the cel for my front 02 sensor and my mpg sucks.. might try some 91 octane

 

It's amazing what a new O2 sensor can do to MPG, especially if your throwing a CEL for it.

 

you should never use 87 for a gsr. no wonder your MPG suck.
i've never used anything but 93 i think used 91 in Oklahoma.

 

ok i have a jdm b16a in my 1990 da should i run 93 or 87 ??? cuz ever since i got the b16 ive been using 93 is that dumb???

 

holy thread jack batman!!

No that's not dumb.. if it was my car i'd run 93 to. Is it tuned? If your running a chipped ecu with some kinda crazy timing or basemap.. def 93. I'm unsure if civic si's require 93 octane, but i'm sure they do.

 

Any VTEC motor should use premium gas 91 to 93 octane, they have higher compression which means detonation with regular 87 octane gas. If your cheap you might get away with 89 mid-grade gas. Newer cars with iVTEC and similar systems will retard or advance timing for any octane gas you use, like the Ferrari's used in the cross-country trip from South America to North America, they used gas with octane levels as low as 70.

 

It really just depends on how you drive. I also got as high as 37 mpg on a highway trip shortly after replacing my O2 sensor a couple years back. The original O2 had over 240K miles on it. I got over 400 miles on a tank of 93 octane that time.

Speed also plays a large factor. If you consistently ball outta control at 80+ mph, you won't get as much MPG as you would driving the speed limit on, say, a state highway with a 55 mph limit.