ACRX8

Will the RX-8 run on regular unleaded or will it need 93 Oct?

ZoomZoom

The Mazda press kit reports that the engine requires premium gasoline.

eccles

The manual for my wife's '02 Miata also specifies premium, but for regular commuting 87 works just fine.

We give it a tankful of premium every now and again, especially in warmer weather or if we're off to a track event, but for daily city use it gets along just fine on the cheaper gas.

ZoomZoom

My understanding is that rotary engines have traditionally used regular gasoline due to their low compression ratios. However, the Renesis engine has a 10:1 compression ratio, hence the high octane requirements.

DreamWarrior

I'd guess "pinging" from low octane fuel may be reduced because of the rotary engine...but I wouldn't want to see what low octane fuel would do to this thing anyway. The octane rating is to keep the fuel from combusting too quickly because of its poor quality, given the rotary I'd thing combusting too quickly would be even worse for this engine than your piston engine?? I wouldn't chance it either way.

73JPS

Best to use what the manufacturer recommends.

FritzMan

Honestly, it's one thing I wish it would do, especially since the likes of Acura RSX (base) can run regular with a 9.8 cr... In fact, I wish all cars ran on 1 grade, so economies of scale would lower the price (don't I sound naive eh?)... The $.10/liter hit for premium gas really sucks.

DonG35Miata

The old first generation RX-7 had a compression ratio above 9.4-1 compression ratio and ran on regular gas. I have heard that they can run on even lower octane ratings than 87, perhaps as low as 80 or even 70. I have always thought that there is something about the rotary that makes it require lower octane ratings than a piston engine with a comparable compression ratio.

Maybe the ignition timing of the Renesis is the reason it needs premium.

By the way, why do they even make mid-grade gas? It seems like cars use either regular or premium- no middle ground. I think maybe one Nissan was designed for mid-grade, and that is the only time I have seen it recommended.

The short answer is that it is just a ploy by oil companies to separate consumers from their dollars with a product they do not need...

FritzMan

Should I get an 8, mid-grade will definitely be what I'll eventually work to (if not regular). I won't be lapping it and it will stay NA.

Yes, I realise that it's kind of stupid to purchase a performance machine and to be too cheap to pay premium... Even though I can afford it, percentage wise over regular gas I find it a rip-off for the amount of octane that is gained. I'd easily trade 5hp to save 12% at the pumps. It's all a matter of watching mileage and seeing if regular gas savings are consumed with decreased mileage. Typically it's not the case.

Honestly, premium should only be on pressurized vehicles. My wife's Volvo V70 is normally aspirated and it also requires premium. I mean it's something like a 2.3 liter 5 cylinder which generates a measely 180hp. Dumb.

Quick_lude

Really? I mean if you can't take the extra $.10 liter cost, you shouldn't be really thinking about a $30K US car no?
Unless you will be driving the car 1000km/week... Personally I do about 500km per week.. at 10L/100 km that's 50L per week or $5/week extra.. or $250 extra per year.. That's a small hit in operating costs imo. Shrug.

ACRX8

Will the 210hp automatic run on 87 Octane? It has 40 less HP.

fritts

I think running regular is about the dumbest thing you can do. The manufacturer recommends premium so use it. Maybe it you had a piston engine you could cheap out on mid grade or even sometimes regular. But we are talking a rotary engine here, an engine that will not take pinging. I guess some of you will have the first Rx-8's in for engine rebuilds. Which just adds to the whole perception of unreliability of rotaries thanks!! I bet that will help us get a new FE RX-7.

khoney

The most knowledgeable RX-7 mechanic in San Antonio told me to run 87 in my second gen RX-7 TII. I've been doing just that for over 16 years. However, the owner's manual only specified a minimum of 87 octane. I guess I'll wat to see what the new owner's manual says. For me, the mileage improvement over the RX-7 is almost negated by the RX-8's supposed premium fuel requirement. Bummer.

91vert

Pinging in a rotary engine is totally lethal. It is much more harmful than in a piston engine.

DO NOT use anything lower than what Mazda says to use in it unless you want to risk blowing the apex seals.

I've never understood why people get so bent out of shape over having to put high octane fuel in a car when it is required for optimum performance. If you don't want to put the correct fuel in the car, then don't buy it!! Smiple as that.

Hercules

In Jersey the price difference from regular to premium ranges from $.15-$.20. With a tank of 16 gallons, what do you spend.. $1.50 more? Big deal. You're buying a $30k sports car, at least don't be cheap about the gas you put in it

I choose Sunoco most times, Exxon/Mobile and BP as secondary choices.

Rich

My brother sold his heavily modified '86 or '87 Turbo II RX-7 a few years ago. On the invoice he explicitly wrote, in all caps, "REQUIRES PREMIUM FUEL. WILL DESTROY ENGINE WITH REGULAR". He also had a bright yellow sticker below the speedo that said, "Minimum 92 octane required".

Needless to say the guy who bought it filled it up with regular and blew the engine within weeks of purchase.

Now, the RX-8 is a totally different beast since it's not a turbo and will start out stock. However, I'm not about to put regular fuel in if Mazda says not to. Besides, at $.20 extra over 12,000 miles a year, that's about $8 a month. $8 a month isn't a big deal to me, and I'm not wealthy. I'll just bag my lunch two more times a month.

Nabob

I find it quite funny that americans of all people are complaining about putting cheap gas in a performance car when their gas is amongst the cheapest in the world, whats the point in saving pennies. I can understand if europeans complain, but for north americans to complain is totally pointless (I live in Canada, where gas is substantially more but still cheap compared to europe and other places)

Aesculapius

5 things us Americans love to bitch about.

1. Gas prices - seriously. If we watched the stock market as closely as gas, we would all have huge portfolios. My IRA swung 100 times more than a stupid gallon of gas in the last 2 years.

2. Taxes
3. Taxes
4. Taxes
5. Taxes

[soapbox]
In addition to paying less than any developed country for gas, we also have one of the lowest tax rates. It's amazing.....like any tax is unfair or something. I would say we are getting a pretty good deal.....low taxes (comparatively) and what we receive is one of the most free and strong (militarily and economically) countries in the world.
[/soapbox]

FritzMan

Like I said, pressurized engines should run premium (and my FD lived a healthy diet of that stuff, in fact I upped the ante an used only Sunoco gold 94), but NA engines? For what, a whopping 5hp (est) through advanced ignition? Don't forget we're talking about a 250hp sports sedan here guys, not a 300+ hp sports car. Pretend all we want (and yes, the 8 will deliver), but IMO, praticality should be made in fuel use as well as number of seats...

In Canada, a 60 liter tank will consume an extra $6 dollars for premium. Yes, if I lived in the States and had 1/2 the gas tax we have in Canada and a dollar which was actually worth something, I to wouldn't mind paying an extra buck or so for premium, but up here, the difference is much more...

Will it nuke the engine using mid-grade or even low grade? Let's put it this way, if the OEM ignition timing is so advanced that pinging could happen on any fuel lower than 92, then don't be driving the car outside of the city, because those remote gas stations will have worse gas (older) than their octane count states - guaranteed.

A large percentage of HP gains from 'chip' tuners is simply through more agressive ignition timing, where in that case, anything less than quality premium will be harfull. But almost 99% OEM cars have a safety margin built into their timing (bad gas, water in gas, deposits in gas, etc...). As a second layer of defense all modern vehicles will automatically adjust their timing to reflect the quality of fuel used...

morganrogers

ref - Gas Tax.

Try living in the UK...
'Super' (98RON fuel) is ~80p/litre
(~ $1.20/litre or $5.50/gallon ! )

Regular fuel (95RON) is ~5-10% less - so still $5/gallon !

Either way - damned expensive....

For the record , my current car requires 98RON fuel , and I pay the extra. I mean I am shelling out £22K (~$37K) fot the car. I ant to get the best from it , so will run what mazda tell me. I would suggest anyone out there should do the same.

Morgan.

Kurt Bob

Here are a couple of additional things to think about:

1. The compression of an engine is raised for one reason - to increase performance. Although many cars designed for Premium (high octane) gas can run perfectly well on a lower octane, they will achieve less power and lower fuel economy. Therefore, the money saved is somewhat negated by the poorer fuel economy.
[I will reluctantly be buying Premium for my RX-8]

2. Many people believe that low octane gas is of a lower quality, which isn't true. The octane (or anti-knock index) of a fuel has to do with its burn "rate." [It helps if you picture the octane chain in gasoline as a fuse] The RX-8 will require a slower burn rate than a NA RX-7.

I hope this helps some of the folks who didn't already know this!

jeremy

chances are mazda, like every other manufacturer, has installed a knock sensor, etc that will retard ignition. i agree its odd that they are requiring premium, but i wouldn't be the guinea pig to f with that and be the first in line for a renesis rebuild. not paying 30k for the car and cheap at the pump.

Cam

iTrader: (1)

In the article from the link in the following thread, it states the RX 8 runs premium gas.

http://www.rx8forum.com/showthread.php?s=&threadid=2115

Quick_lude

Exactly so that's about $300 per year. If this produces a problem for you then why are you buying a $40K Cnd car if you can't afford the $300 per year extra in gas?
What about the $400 Cnd tires each!? that will only last about 30-40,000 km. Why aren't people complaining that the RX-8 does not come with 16" all season $100 tires?
Bottom line, you wanna play you gotta pay. :D

ACRX8

You bring up a good point about the tires!

The 18 on the RX-8 will cost ?? $$ US??