And that has what to do w/ our motor? A diesel is even farther away that our piston counter parts and that much more irrelevant. They have 18:1 compression because they don't use spark plugs and just use heat/pressure to ignite the charge.

 

Glow plugs or bust!

Premium. Premium. Premium.

 

JFC! You win, you're an incredible human being and a great marginalizer of my pathetic life experiences.

I was only trying to relate an anecdote about why high octane fuel is used in some engines, the Wankel included. I felt that diesel knocking was a legitimate tangent to that discussion. I didn't realize that I was being graded on what you would like to see in print today.

In the future, I would be grateful if you would just ignore all of my posts. It's not my intention to bore you or insult your sensibilities. I am truly sorry that I wasted your time. I'll certainly not make the mistake of reading any more posts on this thread.

 

I use premium. Isn't worth the couple of bucks per tank to worry about engine knock.

 

Buy regular and get $2 worth of lotto tickets.

 

I used reg until the last PCM-load. Now I have to use prem or it will MIAC ping. Still runs great and idles smooth.

 

as for pump gas, lowest number possible without pinging is best.

As for specialty gas, the most expensive is best.

But if you're not tuning your engine to take advantage, its a moot point.

 

I've heard the arguments go back and forth endless times on this forum in the year+ i've been here and here's my .02 cents...

With gas already being $3+ a gallon, whats the extra 20 cents or so gonna make? Now, if we were only at 80 cents a gallon, yea, the difference would be severe...but with it barely being an extension of the price, why even buck?

Mazda recommends it for the engines sake, so all things said, I see no reason to argue. It's a sports car...if it gets slightly less milage on premium then on unleaded, big whoop. I'm assuming that it's better for the engine considering it's preferences from the manufacurer recommendation.

 

I ran premium (93) when I first bought my car, but I switched to regular (87) four or five tanks ago...Performance feels the same, MPG has stayed the same (about 22) and there is no pinging, even in a 95 degree autocross on Saturday.

Sure, the price difference isn't that much, but if it makes no performance difference (for me at least) why spend more? Like StewC625 said, it adds up to a couple hundred bucks a year.

 

static said it best.

If there's no tuning, there's no point. If there's no pinging there's no worries

 

Ok I'm pretty confused.

I always thought Diesel's had lower compression than the gasoline engines. I also thought Turbos upped the compression ratio.

I know that octane preference has a direct relationship to compression numbers. Since the Renesis is 10:1, that is a high enough compression to warrant a higher octane gas. I use a 91 octane gas, but also have a choice of 92 octane (big deal eh). I was thinking on higher temperature days, use the 92 (since heat = increase volume).

Any thoughts?

 

Yes. you are wrong.

 

actually you have to use premium cuz i thought the same way i hated the gas prices so i just put unleaded in it and my engine started running alot slower, making some ticking noise from hell, and made my car die randomly soo yeah i hope that ansers your question

 

Possibly for your car, but my near 50K of 87 octane usage - under conditons like 100+ ambient for hundreds of track miles prove otherwise.

No ping, no issues - nothing.

 

ok,

glad you cleared that up...

beers

 

I had this car for almost 2 yrs now, One day I filled 87 octane by accident.Now I have been experimenting 50% 93 oct and 50% 87 and feels the same as before. Conclusion Why pay more?

 

This is my 7th rotary Mazda and the first one I had to run prem-fuel in. The first 20K reg-87 ran fine then with the last PCM-load it started to MIAC-ping. I started to use 89&91 oct and it stopped. I was told on here It could be carbon buildup. I tried several bottles of Chevron-techron and BG44K and went back to reg-87 no help still pinged. What I did notice is if its cooler, say 60F I can run reg without pinging. The pinging only would happen if I gassed it hard and the hotter the weather the easier it would ping. Now that I've retired and driving very little it doesn't bother me to put in a half tank of prem gas twice a month. When I was working I would fill up almost every day, thats how I put on over 520K miles on rotaries. The higher gas gets it seems the spreed between the price of reg to prem is larger. Years ago there were just a few pennies between them. When I bought my first RX-2 in 1970 reg was cheap...and I did all my tuning and could adjust the timing to just under the ping. Now its all electronic and out of my control unless I want to invest and its not worth it to me. I love the rotary and red-line it every chance I get(after it is warmed up). I cant wait for the next gen RX-8 it should be out soon I hope, but Mazda has always been very hush hush.

 

Excuse my ignorance, but what is MIAC-ping??? I know what knocking and pinging is, but is the MIAC part?

 

It all depends on your car and your altitude. Some Rx8's operate with 87 just fine while others tend to have more knocking issues. In my 16 years of rotary experience, I have yet to hear of anyone blowing any NA street driven rotary due to detonation. This isn't a turbo engine (which will have knock levels much higher than any NA rotary). Personally I wouldn't worry about with grade of fuel. Just redline your engine a couple tiimes a week to keep the engine healthy and to avoid what I call the granny rebuild.

 

[QUOTE=staticlag;1944924]as for pump gas, lowest number possible without pinging is best.

AGREE 100%!!!!!

 

The MIAC is "Marbles In A Can" it is the sound that a rotary makes when it pings or detonates. It is something you would understand if you have heard a rotary detonate. Imagine a empty 5 lb can from coffee with a few marbles in it shaken violently. I think that was how it was first said on here years ago. I agree with use the lowest octane gas that works for your car.

 

Its true that you should use the lowest octane you can in your vehicle for a variety of reasons I'm not going to bother to list right now.

However I'm not sure everyone here understands what ping or knock is either or for that matter how the Octane ratings are calculated and what they mean. In short, the higher the octane level the more compression that needs to take place before detonation. If you go with too low of octane level you'll end up with predetonation or what is commonly referred to as "knock".

I personally have stuck with Shell V-power 93 Octane. Simply because I haven't felt like experimenting with the 89 yet. If you feel up to it go for it but as stated above, your savings aren't going to be tremendous. Please don't be one of those people who drives across town to get the best price. You'll only burn more gas on the way over there than what you'll save at the pump.

 

um...have you ever heard of midgrade?

It'd save you a lot of time...

 

Some of the experience with previous automobiles are a moot point and not applicable to this car (or other cars). It has to do with timing. Think about timing as a 1 to 10 range (actually it is degrees of advancement & retardation). If your car is meant to run on 91 and that is a 10, and you get a tank of bad 91 or you purposely put 87 in the engine can compensate by removing timing (in this example going to a 1). But if you get anything lower or in some cases even with 87 the engine can not lower the timing any further and you get detonation. In some cars the engine is made to specifically run on 87, so in that case 87 is the "10" in that range and if you put 91 in that engine your hp gain is negligible as the engine has advanced the timing as far as it will go (ala it is already at "10.")

The human dyno (ala *** dyno) can not feel a 3%-5% power loss that may occur when you remove timing from the car so that is a moot point on feeling a loss of power.

Nobody has really done any extensive test on this particular car with regard to octane & hp gain/loss. A study was done a few years ago by Car & Driver on this issue.

 

Well, specifically for the RX-8 you and I debated this a while back...not trying to get into it again, just stating my personal findings...

I don't have much scientific to offer, but what I do know is that I've run a track day on 93 octane. I then ran the second day on 87 octane. Over the course of both days, my top speeds would be all within the same range - within 1-3mph - before braking zones on the longer straights.

For my car, this is how I ultimately decided to stay with 87.

If I had seen a difference in speeds at the track, or was experiencing ping with 87, I definitely would be using 93.