motors been rebuilt (now has 1700 miles i believe) as well as fuel injectors 300 miles ago. Dont see why higher octane would make a rotary run like crap.

 

But that's what's confusing me.. I got worse fuel economy on 91, and you got worse performance on 87.

My motor was probably around 2.5yrs on my rebuild.. All Atkins internals [All new seals/springs], and [I'm guessing] ~130K housings+159K plates/rotors/Eshaft.

Going by "If the engine is worn or otherwise in poor tune then it will usually run better with a higher octane fuel.", then I should've done better on premium, and you shouldn't have noticed a difference.

Maybe I got a bad tank of Premium [though it was Chevron...] and you got a bad tank of Regular?

 

In other words, through actual experience you guys have realized that the octane rating is NOT necessarily related to gas mileage, burn rate, or energy content.

My red car gets worse gas mileage than my black car, while my friend's red car gets better gas mileage than his black car. How can that be possible?

 

lol not everyone can draw a perfect circle, btw Derekcat mine also has some Atkins internals so yea......

 

When I bought my turbo II I have always used chevron 91. It sucks now with the price being over 4.50/gallon. I haven't tried any less to find out what happens. I use chevron in all my cars and motorcycles. I think its well worth the price difference.

 

4.50 a gallon you guys have got it good, here in not so great britain it costs me the equivalent of $160 to fill the tank with 91, at least 60% of that is tax.... We get raped by our government daily. I ****** hate england it sucks.

 

damn man, 160 usd to fill up! have you visited the states b4?
how many gal you fit in your tank, and arent your fluid measurements a bit different than ours?
btw, i run 91 all the time since i sent my injecters to witch hunter after i bought the car.

 

I am running 91 octane on my 93 FD TT, but I have a bunch of aftermarket upgrades.

Should I be buying higher than 91 octane?

Like buying additives?

 

If the car is running OK then the 91 is fine. If the engine starts degrading then you will probably first notice problems at very high ambient temperatures and/or during high-load conditions (driving up a steep hill, rapid acceleration at high boost, pulling a trailer, etc.). If this happens then stop doing whatever seems to be causing the engine problems and take the car to a mechanic.

Aftermarket additives are bullshit. If you have a lot of engine modifications that make the engine more prone to knocking, then high octane race fuel, a more efficient turbo and/or intercooler setup, better tuning, and anti-detonant injection are all better alternatives to "snake oil" fuel additives.

 

Okay, that makes sense.
I never really understood those additives.

 

i drive my car quite often on long trips(~1000 miles round trip to cali), i use the cheapest gas stations i can find but of course always use 91. of course i still have S4 TII rotors in my engine so it will be less prone to issues but i run it at 15psi regardless of what gas station i just pulled away from and the motor is still in one piece after many many years.

about the only difference you'll notice power wise depends on the station and how much ethanol content the fuel has and if the fuel is oxygenated or not(oxygenated fuels get poorer fuel mileage but is supposedly better for the environment).

me either, because if you read the fine print on the back of those stupid octane booster bottles you will notice it only adds fractions of a point to your octane rating. so basically you'll need about 50 of those little bottles to a full tank of gas to get to the "100 octane" rating that it sais on the front of the bottle. at which point a force inducted car would blow up due to running lean anyways(which is why most of those come in small bottles since they're usually based on alcohols which have higher octane than pump fuels).

"more power" my ***..

 

Now that I got my T2 back, I again only use 94oct and Premix. 1:250 ratio because I still have the E-OMP and the thermowax pellet modification done.

 

I've got about 25k on my t2 now premixing 100:1 and I've only been using Chevron 91. Top tier gas really isn't that much more expensive then the cheap ****. I notice somewhat worst fuel economy as well when filling up with cheaper gas. Not necessarily a change in performance under heavy load but also my spark plugs are a lot cleaner than my last fc that I just put whatever gas was cheapest in. I wasn't even premixing that car.

 

hahaha Ethanol is wayy cheaper here with E85@$3.05 and regular 89 octane is $3.85

 

E85 is cheaper everywhere, because you use more of it to go the same distance.

if you find a station that charges more for E85, they're just capitalizing off the treet huggers because there is limited stations nearby.

 

FYI ethanol sucks, which is why people like Primos003 avoid it.

E85 causes about a 30% reduction in gas mileage. Therefore, add 30% to the price of E85 to get a rough estimate for a comparison to regular unleaded. For example, $3.05/gal * 1.3 = $3.965/gal. Also, keep in mind that you would need to fill the tank more often, and E85 reduces engine power. The FC RX-7 isn't rated for E85, so you shouldn't use it anyway.

E85 is expensive to produce. The only reason it is cheap is because it is subsidized by state and federal taxpayers. Yes, that's right, government wastes billions of your tax dollars on this crap.