Regular Grade Better than Premium?? WTH??
 

Ive been reading alot that regular 80-octane range gas is better than the premium 90-octane range gas. wat the heck is going on? i always thought that at the 10:1 compression ratio, higher octane levels are needed such as in turbo... confused.. Which grade of gas do you guys use and does it make a differnece? i mean... 20 cent difference can add up to save alot of money.. dont want to be using premium for no reason.. also wondering about long term effects of using regualr... such as buildup in engines, etc etc..

Yeah, can somebody explain this regular gas versus premium controversy?

I personally do not wish to be a ginuea pig more than I need to be...

I tried regular gas as an experiment and although my mpg got a little better I don't think I will do it again. I took it out onto the interstate and punched to pass some traffic and right at 6000 rpm it sounded like someone pelting the windsheild with rocks! It scared the bejezzus out of me. That was the first time I experienced knocking in a rotary if that is what you can call it. it sounded like the engine was fragging itself.:eek:

I tried 3 tanks of regular and 2 tanks of mid grade about 500 miles ago. My gas mileage did not improve in around town driving, it also did not get worse. The only thing that I noticed was a little less responsiveness in high RPM's and torque when taking off at lights or after being stopped. I had multiple stalls when taking off at low RPM, when RPM and clutch action was the same as I had done with Premium fuel. It just apperaed to give it a little more grunt when getting the car moving. Nothing really quantifiable, just perceptions.

Bottom line is you want the lowest octane rating gas that your car will run without pre-ignition. Not necessarily for economy, but for max. power and efficiency. How do you determine what to use? Unless you know how to tune a car and have a good knock sensor system, go with what the maker recommends. There are some fancy aftermarket knock sensors available now (check NASIOC forum - Subaru). They tell you the level of knock with great sensitivity. The way to go if you want to experiment.

you guys should read canzoomers thread about boosting power, I think you should search under "dynoing the 8", he said that using octane 87 is perfectly safe. You guys can read the manual too, 87 is perfectly fine.

There is nothing in the manual about 87 working perfectly fine. It says: " You may use a regular unleaded fuel with octane rating from 87 to 90 but this will slightly reduce performance"

I am on my 23rd tank of gas. The first 12 were premium. The next 5 tanks were regular and midgrade between 87 and 91 octane gas, and I experienced noticeable slightly reduced performance. I went back to premium in my last 5 tanks and the reduced performance I experienced never returned.

My reduced performance was, sluggishness above 6000 RPM and a noticeable lack of torque at the low RPMs, when getting the car rolling. The starting off in first gear could have been remedied by increasing the RPMs or slipping the clutch a little slower, but I knew that these alternatives were not needed with premium fuel, because I had just driven 12 tanks with none of these problems.

My experience with the different types of fuel, resulted in me returning to premium because of the slightly (but noticeable) reduction in performance I was not willing nor enjoyed living with. Had I not run premium first, I might not have noticed the difference, and still been happy with it.

I don't think it hurts for each person to try it and see if its worth it to them.

I am switching between 87 and 91 depending on the $$$ at the pump. I think this should help me save $$$ as the weather gets colder:D

i dont know about you guys, but gas over here in cali is hell expensive.. premium goes for almost 1.98/gal.... also, does using chevron gas really help keep your engine clean? just wondering if the same techron stuff helped out the rotary engine...

I just use mid-grade(89)

I have been using mid-grade 89 octane for about 3 months and have noticed no discernable difference. The car is smooth in all performance areas (acceleration, turns, hot/cold weather.)

I used 89 octane the last few fill ups...which is every other day with my low mpg!! I notice a slight reduction in performance and maybe in summer time I will go back to premium.

I'm actually curious as to how the engine will respond to VP Unleaded racing fuel...

100 Octane fuel :)

At least the pre RENESIS rotaries ran great on lower octane (N/A only!). Because of the fact that the car does not have valves, but ports instead, fuel does not always completely burn in the combustion chamber...hence the popping backfire noise you hear in older Rx-7s when shifting at higher RPMs. Because even 87 octane makes the car backfire, 91 octane will only make things worse because it takes even longer to completly burn a higher octane fuel. Now that the RENESIS engine has different intake and exhaust ports that don't overlap, I am not sure if this "popping" noise still exists (have not heard it on the RX8s I have driven so far). Either way, the fact still remains that it has ports and is a N/A rotary engine. Unless you are advancing the timing on your engine for better performance or turbocharging, there is no reason why you cannot run 87 or 89 octane in the RENESIS motor. Don't forget that QUALITY of fuel is important here too. Chevron 87 octane will probably perform better than a cheap grade 89.

Happy Rotoring,

Kurt G.

There is a big difference between the renesis and the 2nd gen rotary - the renesis has 10:1 compression ration, whereas the 2nd gen was in the low 9:1 area.

As for clean burning fuel, I have had very good results with the 10% ethanol premium in my 3rd gen. and Pathfinder.

what would happen if you filled up on 87 gas but added an octane booster? wouldnt the octane grade go up? plus, what would techron do for renesis engine? if it doesnt do anything imma stop buying it. it costs like 2 cents more than just regular.. ( that is IF you out of cali people have chevron with techron )

It's been a while since I wandered the forum. Hi all, finally got my 8, I'm at about 4000 miles now! On to the topic!

Starting off fuel additives. The claims on the bottles say 1 to 2 points. What's a point? Usually a tenth of a value. So adding a bottle will turn 87 octance to 87.1 octane. Probably not a measurable difference. At $4 a bottle, not a good investment. Adding Toluene might be a cheaper solution. Internet wisdom states that one should not exceed 30% toluene mix. That comes out to 4.2 gallons of toluene for the RX-8's 14 gallon tank. Assuming you start with 91 octane, you'll end up with 97.9 octane fuel. Assuming that 91 octane is $2 a gallon and toluene is $5 a gallon, it comes out to $2.90 per gallon.

On to 100 octane fuel, from a SoCal perspective. It turns out Unocal holds a patent for producing high octane fuel cheaply and legaly in SoCal, so only 76 gas stations carry it. At prices ranging $5 to $6 a gallon, quite expensive. About the same price as our Japanese drivers across the ocean.

So pulling several thoughts together.
1. The JDM RX-8 still claims to make 250hp. They never stated what fuel they are running, I'm assuming 100 octane or better, meaning they can tune much more aggressively.
2. There's a lot of soot in the exhaust. This might be due to burning excess fuel? The ECU is putting more fuel in because it's afraid of pre-ignition?
3. The 10 : 1 compression is quite high for 91 octane. This compression ratio should be running 100 octane fuels.
4. Looking at other modern ECU's, they seem to adapt to different fuels very well. Sports Compact Car had a WRX that responded very well to high octane fuel. I bet the RX-8's ECU is constantly reigning in the fun, as in 91 octane is not sufficient to run at 100% efficiency. The manual states 91 octane as minimum because that is highest commonly available octane in SoCal.

So my plan of attack is this Thanksgiving weekend, get a baseline with my (very old 1st gen) g-tech accelerometer. Run until about half empty fuel tank. Fill up with 100 octane from my corner 76 gas station. This should bring me to about 95.5 octane. Run another test. Hopefully the 4 octane difference is measurable. If not, I blew $35 out the exhaust pipes!

About 2.30 where I'm at..

still nobody told me anything about the techron gas addative... i know it does goods for the piston engines but im wondering what it does for the rotary, if anything...

I would think it would at least help the exhaust ports stay nice and shiney...

Union 76 for 5 bucks is fair...but I'll try and get some VP since the shop I used to help out at hooks me up for about 3.50 a gallon...I'll get back to you guys.

BTW...250 PS does not equal 250 bhp...I know that in JDM land, the Integra GSR's were putting out 180 PS while over here ours put out about 170 bhp...

Just a follow up. The Unocal 76 by where I work no longer carries 100 octane unleaded. So no convenient way for me to test and I'm not willing to add 30% toluene and run the risk of damaging the emissions system.

Anyone know who else might carry 100 octane unleaded in SoCal near the 23, 101, 405, 118, 5, and 14 freeway? Not that I'll be making regular fill ups...

Also of interest is this compilation. I guess I could play hookie from work and visit the Pasadena Unocal on the way up the Angels Crest Hwy.

there is no difference in quality with lower rated gas, just lower octane.