Car can't handle 87octane

[NotchRocket92]

Hey guys. Not really a question just looking for some thoughts from you all. I drive pretty much basically the same all the time and for some reason with 87 oct fuel I can only get about 150 miles to the tank. Premium fuel I can get 200-210 miles to the tank. Does that seem odd to anyone? Also, whats even more weird is that the car is completely stock and thats all I get to a full tank. Just replaced plugs, cap and rotor and did oil change and not much of a difference. The plugs don't look to old but im not sure of the shape of the pcv valve or the o2 sensors. Any ideas? btw car is a 94 GT AODE 105k mi.

 

[wytstang]

It some what makes sense seeing as how higher octane fuel is slower burning maybe that has something to do with it . I would check the timing, change your fuel filter, and air filter. Is that your car in your avatar? if so by all means post some pics.

 

[NotchRocket92]

Wyt,
its just a pic I found online (attached to post). I'm part of the Laser Red crowd not the Boss crowd unfortunately lol. You really don't think it would be o2 sensor related?

 

[1105]

change your fuel filter first. It probably needs a new one anyways because I can almost gurantee you its still the stock one. I'm getting 215 to a tank with the mods listed in my sig which still isnt as good as it should be, but I have a lot more done than you and I'm getting the same mileage to a tank and I still have in the stock O2 sensors.

When you take the old fuel filter off, see if you can blow through it... If its hard to blow through it was clogged, if it was easy that means it is still good, but couldnt hurt to be replaced anyways.

 

[BlackVert]

my car doesn't seem to like 87 in the winter. it just recently started hesitating at low rpms with 87. with 93 octane, it is much better.

 

[HISSIN50]

sorry if i missed it, but what is your timing set at?

 

[DFG 5OH]

i run 89 all the time and my car runs fine, 93 is good, and 87 it will ping a little to much. Give it a good tune up and see what happens.

BTW i thought higher octane fuel burnt faster, and that you would get better milage from 87 than 93???

 

[HISSIN50]

i run 89 all the time and my car runs fine, 93 is good, and 87 it will ping a little to much. Give it a good tune up and see what happens.

BTW i thought higher octane fuel burnt faster, and that you would get better milage from 87 than 93???

nope, Wytstang is right. the higher the octane, the less volatile it is. since it does not ignite as quickly, one can run more timing. make sense?

 

[Darkhorse845]

My stang seems to run good on 87 octane
all year thats odd!

 

[CManT1914]

Mine runs fine on 89 depending on where I get it. One brand gas 89 sucks, so I pay a few cents more for the better brand 89 instead of 10 cents more for crappy 93. Maybe you got crappy gas, lol. I get about 210-220 miles out of a tank, and that's usually around 17.5 mpg, so maybe you need a tune-up. Like somebody said, check your fuel filter. In my old car the fuel filter and fuel pump was going out, and it was running real bad and getting bad mileage.

 

[bgorrell]

If you normally go to a particular gas station, try using a different one for a while.

I'm in the military and refuse to go to the on-base gas station anymore. Twice, my stang wouldn't stay running after filling up there. The whole way home, as soon as I tried to shift or came to a stop, the RPM's dropped to 0 like a ton of bricks. Adding a bottle of Heat to the tank restored it to working condition each time. It has not happened for a year now since I switched gas stations. Others at work have had similar experiences. It's probably a case of going with the cheapest contractor or having old in-ground tanks.

 

[mo_dingo]

That makes absolutely no sense. The lower the octane, the more effecient running it should be.

I would start with the simple stuff, plugs/cap/wires/rotor, check fuel pressure, vacuum, clean your MAF, replace your IAT/ECT, etc. Then try swapping O2 sensors. You can get new ones on www.oxygensensors.com for pretty cheap. The o2 sensors are the main control for a/f ratio during part throttle cruise, so if one or both are old and corroded, etc, they definately could be your problem.
Scott

 

[rgs]

you think thats bad? i get around 175-200 KM per tank

 

[Shakerhood]

Where you set the timing determines what grade of fuel you need.

 

[tderrick]

BTW i thought higher octane fuel burnt faster, and that you would get better milage from 87 than 93???

High octane fuels were designed for high compression motors to avoid pre-igniting on the compression stroke.

In other words, the pressure itself is enough to ignite the mixture...

ie; it burns slower / slower to ignite

 

[mo_dingo]

Where you set the timing determines what grade of fuel you need.

But running 18* of timing and 91 octane only gets you a higher gas bill, not more power. Running the most timing you can without going to a higher octane is the only way to gain power from it.
Scott

 

[BlackVert]

i get about 30 more miles per tank on regular than i do on 93 octane gas.

 

[CManT1914]

High octane fuels were designed for high compression motors to avoid pre-igniting on the compression stroke.

In other words, the pressure itself is enough to ignite the mixture...

ie; it burns slower / slower to ignite

Yep, that's the whole concept behind diesels.