Any thoughts about using mid-grade gas during the cold weather months?? Here in California premium is fast approaching $4/gallon. Would there be any damage to the 8 engine by using 87 or 89 and revving to redline? I'm new to rotaries, but piston engines usually knock due to high ambient temperature/low octane gas. Is it the same with a rotary? I could trade a few revs/hp, if it is safe, for a long freeway trip where engine speed/load is light and save a few $$ in the process.

Any thoughts, suggestions are welcome.

I just put in 89 for the first time, haven't noticed any issues yet. I believe what works varies by car, as some here seem to be able to use even 87, while others have had issues with anything less than 91.

Not worth the risk. Sell the car or get a $1500 beater. $1500 can get you a reliable FWD beater.

i've run 87 every fill up for 4 years. i think quite a few people do that.

fyi: i was new to rotaries when i got mine, and using 87 came from the sales guy AND the mazda head tech (not that they necessarily know by experience, but they have to at least know what if they are wrong, THEY will be footing the bill on my repairs, so it seems safe to at least assume they really believe that 87 is perfectly fine).

Does the Renesis Rotary have a knock sensor that retards ignition timing? I understand that if so, I will lose hp. My main concern is durability as I love revving the crap out of it.

I only risk it every now and then when im broke

I recently did a 1400 mile drive putting mostly 87 in it for every fill-up except one with no issues. I do still try to put 89 or 91 in it occasionally, especially since 91 usually has the additives for cleaning your fuel injectors.

87 used here (mostly Chevron), with the occasional redlining. No issues.

I have been running 89 since day one with no problems after close to 22k miles.

dont worry, we pay pretty much $5/gallon for 87 in canada and thats what i use with no problem.

I put in my first tank ever of 87 just to see.

Predetonation is not good for ANY engine.

i wouldnt risk it.
i use 91 and i have no problems. its only about 2-5$ more a tank
so why risk a engine if your only saving a few $$ ?
1000+ $ for a new engine doesnt sound good to me. i'd stick w/ 91

87 runs great for me, nice and smooth, no ping, no power loss... but warranty would cover my engine if i ran it with dynamite.

I have used 89 in the cooler months but not in the summer here.
The way I look at it is,, $0.10-11 cents per gallon saved by going to a lower octane. 13 gallons per fill up. $1.30-$1.43 per tank difference between 89 and 91 octane. If you fill up 10 times a month,, $13.00 - $14.30
Thats about $0.44 per day that you would pay extra for using premium over mid grade.

Is it worth it?

Dont kid yourself. If you use 87 octane your engine is struggling with predetonation. Thank your anti-knock sensor for retarding your timing to compensate for ping. Thank it again for a loss in power. Just not worth it.

I never use premium, regular works great.

I just use Premium, in NYC 93 is Premium.

Sunoco has 91, but I never tried it.

the diffs between Premium to *Medium* grade is about 10 to 15 cents.

Ahh, big deal. Im ok to pay an extra buck or 2 every fill up.

using 87,89,91,93 octane fuel you will always have "predetonation" because it hasnt detonated yet.

low octane fuel (regular) works just fine for me with no ill effects what so ever. No ping, no detonation, the ecu isnt messing with anything and its running happy.

Maybe granted in higher ambient air temps lower octane fuel might (might) cause problems.

I have driven a car that 100% absolutely needed 93 octane! i was stuck at a station with either regular or diesel, put in the lower octane and it drove ok until it started suckin up the new gas.... pdddddddddddddddddddddddddddddddddd, and when the ecu messes with your timing and shit you cant get the sucker over 1500 rpm

Nothing wrong w/ running 87 in your renesis. The old FC motors had 9.4:1 and 9.7:1 compression ratio and ran better on 87 than 91. Mazda once raced rotaries on the 87 until forced to change.

Unless you have a hairdrier under the hood you can fill up w/ 87. Been doing it for 11K, and w/ every n/a rotary I have owned. There is some funny info on 8 club from time to time IMO.

Isn't knocking a heat issue? So with winter here, why worry about it.

It is a heat issue. Down here in Phoenix I get detonation on 91 octane. All I know is I can't use 89 or 87 at all if the temp is above 70 degrees. If the temps drop into he 60's. I can use 89. But as I posted earlier why risk it.

I don't see how some pinging can hurt anything. I'm a machinist, and the metal in the motor is much stronger than the pinging.

http://www.rx8club.com/showthread.php?t=121249

don't you do this?

The problem occurs because the timing of the detonation is not at the rotational point of power, It occurs before the correct engine timing point. Thus causing stress on all the parts. mainly the apex and corner seals.
Picture a piston engine firing way before top dead center on the compression stroke. The piston is moving up from a cycle from another piston. Suddenly the AF mixture lights as it's coming up. Basically combustion wants to stop the piston as its moving upward. Think you would get some stress there? On the piston rod/crankshaft.
Same scenario with the rotary. your trying to push the rotor backwards against it's basic rotation. That is why timing is very critical. Otherwise KABOOM!

Yes I've read that thread. Where I live the ambiant air temp can reach 125+. And we also have no humidity in the summer time here. Maybe 6-10 %.
Compressing air also creates heat. With high intake temps and low octane the fuel with the slightest bit of compression wants to ignite on it's own.
Now cooler climates and higher humidity will play into the picture also. Slowing detonation. That's why some people in cooler climates have no problem with lower octane.

^ we are about to get a snow storm today. ( 4 - 10 in ),,, trade you.

Otherwise KABOOM!

gotcha

^ we are about to get a snow storm today. ( 4 - 10 in ),,, trade you.

Well,,,,NO.:icon_no2:

Remember IAT is NOT ambient.

Higher octane, lower cost.

Mixing 4 parts 87 with 1 part 93 will result with about 90-91 octane.

Most people don't know that.

I put 3 gallons of 93 in and 9 gallons 87 (3:1). Just under a buck a tank more, where filling with 89 would be about $1.85 more. I do the same with my CX7, and burn 2-3 tanks a week of gas between the two.

BTW, if I run 89 in the CX7 it knocks noticably. Mixing it 4:1 doesn't, so its a safe bet mixing it at 4:1 results with higher then 89 octane.

^ Check your math. (4(87)+93)/5=88.2 not 90-91 and that assumes linearity. And that would be 4:1 not 3:1.

And (3(93) + 9(87))/12= 88.5

All that work to save .85 a tank?

Valpac is on a mission to correct us today. LOL

^ Check your math. (4(87)+93)/5=88.2 not 90-91 and that assumes linearity. And that would be 4:1 not 3:1.

And (3(93) + 9(87))/12= 88.5

All that work to save .85 a tank?

It's not "linear".

It takes about 30 seconds extra per fill. May not seem like much but over a year thats about $170 for an hour's work, and thats after taxes.

It's not "linear".
...


so how did you arrive at your figures? formula?

here in pa if it is cold i'm talkin 50 or less 87 worked fine for me but i parked it now and drive a nice $350 1988 plymouth sundance lol........summertime its only 93 octane for me and nothing else only 20 to 30 cents more per gallon....thats why I work to pay for stuff

Given how advanced modern-day ECU's are I really doubt you'll have any problems with running a lower-octane gas. You'll just run the risk of losing a little horsepower I'd imagine.

Valpac is on a mission to correct us today. LOL

nah, not really. its just there is so much info that is just thrown around carelessly thats all.

i've been running 87 the last few weeks. normally i run 93. i've no problems whatsoever. i cant tell a difference in power or sound. or anything.

i run chevron gas exclusively, whether its premium or normal.

I used 91 for the 1st year 87 for the last 2 1/2 years. It seems to run the same. I get 22 - 24 mpg on country roads and hit 9k at least 1 time per drive often shift around 7 - 8k while accelerating. Great car

I have a 2004 that has run almost exclusively on 87 with the once in a while 91 or Shell V-power. No problems at all and I feel no difference in performance, doubt that the average owner would unless really into racing, etc.

From the 04 Owner's Manual
"Your Mazda will perform best with Premium Unleaded 91 Octane
You may use a regular unleaded fuel with Octane Rating from 87 to 90 but this will slightly reduce performance. Fuel with a rating less than 87 could cause the emission control system to lose effectiveness. It could also cause engine knocking or serious engine damage."

Note that they also say never to add fuel system additives or cleaning agents other than those specified by Mazda (but how many of us are talking about pre-mix, Techron, Seafoam, etc???? Why would we question the use of 87 Octane but consider additives?

Personnally I am using Idemitsu Pre-mix (6 oz when I fill up at the light about 13 gallons) since about 60 K miles after reading the entie thread on Pre-mix I felt that it is a little additional insurance. BTW original engine...76K miles now and never had any engine problems. Did all the recalls and do all of my own oil changes (Castrol dino oil) and plugs.

In areas of extreme heat or FI applications, I can see the higher octane helping. Whatever works for each owner but if you try 87 make your own decision on performance. Many of us are using 87 without any problems.