ken-x8

That's the intended purpose. But it also prevents dieseling on some cars.

I had a BMW 2002 that ran OK (no pinging, and this was before the days of knock sensors) on 87. But when I turned the key off it would keep on running. If I used mid grade or premium, it would shut down OK.

Ken

SayNoToPistons

iTrader: (8)

Yes... and the econoline van is a sport car according to Ford.

zeblien

LOL Ya well according to all car manufacturers for every car they make:
1.) This car is a sports car made for the family with 4x4 off road capibilities and a class c tow hitch.

2.) It gets the best gas milage in its class.

3.) Recieved the highest government crash ratings in its class.

4.) Prices starting as low as $6500.99 or $10.98 per month!
So ya, the eccoline and the scion are sports cars.


(and dont make fun of the scion xB. I drove it for work and its great, although a bit slow on the getup.. and cheap).

MazdaManiac

iTrader: (3)

Precisely. Though, you do want to run the lowest octane you can that reliable avoids ping.

There is no such thing as "predetonation".
There is detonation - the uncontroled expansion of the ignited fuel charge, and;
pre-igntion which is the spontaneous auto-ignition of the charge prior to the intended igntion event.

EFI engines can't "deisel".

RoXanneBlack8

if you are so strapped for cash that u need to save 2 bucks per fillup, u wouldnt be owning a rotary now would u.

if it ran better and faster or whatev else u ppl think is good on 87 octane, they would tell u to run it on 87. i run 93 until the day i die. if they sold 95 id run that. the 2 bucks a week is worth the piece of mind to me. i get 18mpg city and i am plenty happy that a rotary can reach that.

wanna save $? sell it and get a corolla

zeblien

No sell it and get a Scion. But sell the car to me for $25 bucks. I would give you more, but i need to save money for gas for my 8.

DrDiaboloco

Am I the only one who tunes out and moves on when posters use "u" instead of "you"?

DrDiaboloco

I didn't say I AGREED! I thought the "4DSC" bit was hysterical 15 years ago and continue to think so NOW. Actually putting a sticker on the car proclaiming this is a bit much.

ken-x8

That BMW wasn't EFI. And on 87 it kept on running after the ignition was off. Not all that well, but it kept going.

I don't know if I was also getting preignition - there wasn't any pinging and it seemed to run as usual when the ignition was on - but I do know that octane made a difference for the run-on.

I have no idea what secondary effects octane has on a rotary. But I'll take Mazda's word for it on what fluids to use.

Ken

Tamas

iTrader: (1)

No.

Silver_Surfer

LOL! maybe you should've kept the box or start running 87

Red Devil

You are inferring these statements based on what? You act as if the answer for you is all encompassing. I run 87. I'm not strapped for cash. My car experiences zero detonation even under pretty extreme conditions. So why would I use 93? Because Mazda "recommends" premium? To me, that is just plain foolish. If my car was experiencing detonation with 87 octane, then I'd use premium, but it doesn't.

I guess I'll take my couple bucks of saved money a week and have a Guinness at the bar. Cheers.

Raptor75

Ignorance is a poor defense of your choice. The fact that you don't understand how or why the rotary dose better with 87 then higher grades is not a good reason to use 93 Octane. Mazda has said many things which were not exactly accurate, yet served their interests better then the true fact. Many rotary race cars run with the lowest octane they can find, I have heard as low as 80 octane, of course I guess they just don't know it would run better at 93 or even 95 if they could yet it.

It is your prerogative to throw your money away needlessly, if you owned the car for 10 years you'd be spending an additional $1,500 on gas. If this doesn't bother you I have a $10 candy bar I'd like to sell you.

Smileynh

Ok, so now the reason to use 93 and not 87(see below). So the question really is ... What does Mazda say about the 8 using high octane gas? Does the engine work better on it or not? My experience says that my 8 gets better mileage on lower octane mid grade. Does that mean it also has more power in that band of gas? I'm not sure, but I'd also never put 87 in it risking engine damage.

The Mazda manual online says Requires 91 octane. So I'll use 91 and 5w20 non-synthetic oil.

Does High Octane Gas Give More Power?
No. Unless your car is explicitly designed for high octane gas (see your car's manual), using a high octane gas will NOT improve the power output of your engine. Again, the octane rating relates to how much energy it takes to ignite the gas, but NOT directly to how much energy the gas puts out.

Exception 1 - By Design

One exception is with engines or cars designed for high octane gas. In that case, using high octane gas WILL improve performance and mileage. The reason has to do with the compression and ignition timing characteristics of the engine. Those specially designed engines will only perform efficiently with higher octane gas. Most engines are not designed this way.

Exception 2 - Engine Knocking

The second exception is if your car has a lot of engine knocking or pinging. This is a sign that the gas is not igniting when it should. This reduces the power and efficiency of the engine. Assuming your car's manual says it's okay, using a high octane gas can help.

BlueRenesis82

+1

zeblien

Maybe thats whats wrong with engines these days then... the octane additive. If we just used 0 octane gas, we wouldnt need sparkplugs, or starters for that mater. We could just bump the car to start the ignition process and off we go!. And since each octane grade is 10c more expencive, 0 octane should be free. True, we couldnt stop the engine very well, but who cares leave it running... its free gas!

Planet Pluto > Guinness > coors light == water > miller light.


Edit: Equasion above has been editied as suggested.

Smileynh

coors light == water

Sorry to break your equation.

Silver_Surfer

AGREE 100%!!

Some people think higher(Octane) is better. Does not equal to more power.

Fanman

It does if the engine's timing is set to run optimally at 91 octane. An engine's timing is not an on/off switch, it is set in degrees, and the car's computer constantly retards/advances timing based on the conditions the engine is running in. Think of it as a range of 1-10. If 87 is a 1 and 91 is a 10. If you go below 87 octane (as a few people who have gotten bad gas have the engine can no longer retard your timing that far, and you begin to get detonation. On the other end, after 91 octane, the engine has advanced the timing as far as it can and it won't go further than that, hence you are getting the maximum amount of hp you can from that engine.

So in some cases higher octane does equal more hp, as the ECU will retard the timing if you are running less than recommended octane gas. What the manual states.

This is an article from Car & Driver that examines this issue. In this case they tested 3 cars that the manufacturers state run on 87 octane normally, and even if you put 91 octane they only gain a few hp. Again, read my example above on the 1-10 scale for these cars 87 octane is 10, so going beyond that nets you very little. However, the cars that are supposed to run 91 octane (Saab Turbo & M3) suffered about a 6%-10% decrease in performance/hp with a switch from 91 octane to 87.

http://www.caranddriver.com/features...r-premium.html

Silver_Surfer

Fanman, in all fairness you should have inculded Reddevils thread....

Most any engine under pressure, S/C, T/C or high compression engine will gain more HP than fairly modified N/A engines using higher octane, slower burnning fuels.

Raptor2k

So in the case of the Renesis, I guess that performance can vary by either being slightly better with 87 OR slightly better with 91-93, depending on the engine's tuning? The forum seems to be very split when it comes to what gas gives more power.

DrDiaboloco

I routinely use 87 when I'm doing all-highway running. No ill effects and I don't need that last 6-10% of horsepower for constant running at 3-4000rpm. That last 6-10% of hp is irrelevant in this case... No pinging means everything is OK as far as I'm concerned, esp. since the manual doesn't PROHIBIT it. There's even a line of reasoning that says the 87-grade is better for mileage.

Fanman

Not really as much about FI'ed engine, as it is an absolute requirement for my setup, but if you look at a high compression engine such as the M3's, or ours, it needs the 91 octane as well to have the optimum timing. People point out previous threads on the RX7, but realize that those engines are very different than these engines. The compression ratios are far higher on this engine than previous 13B units. Not about gaining hp, it's about where the engine is set to run optimum timing.

Absolutely true. For some people the 10% might not even be noticeable if it is an everyday, freeway car. But some of the people are claiming no difference and that is not true. Some people don't care about 10%, some people do. It's up to the individual.

That's not the way it works. Essentially it doesn't mean that some Renesis give more hp on 87 & some on 91. The article has to do with different cars. Ones that are programmed (timing) to run on 87, run optimally on 87 and as such do not get much more hp from running on 91. Ones that are rated to run on 91, lost 6%-10% of their performance running 87. It's just what is your definition of performance ? For some people it is max hp. For some people it is smoothness, or better gas mileage, and 5%-10% less hp may be irrelevant. Butt dynos are notoriously inaccurate.

Nubo

I used to be staunchly in the 87 Octane camp.

Then, I changed the plugs at about 14,000 mi. Even though I'd never heard anything that sounded like pinging, I found that both leading plugs were missing a bit of insulator near the tips. This is a classic sign of knock. While I can't be sure whether or not that was the actual cause, I decided I'd rather have the larger margin of safety from higher octane. In a few thousand miles I'll check the new plugs to see how they're holding up.

This is the worse of the 2 leading plugs

Silver_Surfer

Nubo, that is a terible looking plug! This is the kind of stuff I'd wanted to see/here when starting this thread, not the here say/read that stuff. Can you tell me about your 8. Mods? If any.