rclopez3

I read this article that basically said that no car really needs premium gas. So can I put mid-89 or even 87 Gas on my 2005 RX-8??? Would anything happen to my car??

Fanman

Discussed about a 1000X. Try using the search feature. Short answer. You want the hp you have to get the premium. You can run on 89/87, the car just retards the timing in the engine and you lose a bit of hp. If you get any bad gas (below 87) you start to detonate.

carbonRX8

iTrader: (1)

If you would have searched you would have realized that the new plastics that are used in the RX8 gas tank will react with low octane fuel and precipitate on the fuel pick-up and on the oil dipstick as a white, frothy paste. This paste will clog your injectors causeing a lean mixture that will detonate and push your apex seals out your periferial port. Your best bet is to get some lead-containing octane booster and put 1 gallon in for every 5 gallons of 93 octane fuel.

rclopez3

Thanx, I am just getting use to this site. Next time I try to search.

Thanx again!!!

tjbourgoyne

Rule of thumb - stick with the owner's manual. The brick head on the evening news doesn't know anything about your car and even Mazda dealers give bad information out. If you need more guidance try the search.

Conundrum

iTrader: (1)

Copy straight from the 2004 RX-8 manual.

Read and understand the manual first, if you don't have one, MazdaUSA has then in PDF, you just need to sign up first.

https://www.rx8club.com/showthread.p...ghlight=octane
https://www.rx8club.com/showthread.p...ghlight=octane

There are couple more, but just to get you started

StewC625

Ok, ordinarily, I'm relentless about flaming non-searching noobs, but JUST THIS ONCE, I'll be nice and give good info out.

I regularly cycle between premium (93 octane) gas and regular (87 octane) and I cannot tell any difference whatsoever. I get the same mileage (crappy), the performance seems to be the same, there's no discernable knock, etc. I only use BP, Mobil or Shell gas. No convenience store crap.

That said, for some reason, about half the time, my conscience gets me and I fill it with premium, and the other half of the time, I buy regular, again for no reason. I've even done WOT acceleration tests between the two fuels, using my G-tech meter to time 0-60 and quarter-mile times and I see no repeatable performance difference - i.e. in any given run I can get up to a full second of variation in time due to how I launch the car, how well I shift, etc. - if there's any measurable performance difference, it's buried in the variation in run times.

That said, I have heard that if you want to run regular, you're safer doing it in cooler ambient air temps, where the cool incoming charge air is less likely to detonate. I generally run regular all winter long - starts fine, runs fine. In summer is when I start vacillating between prem and reg.

Raptor75

Same here, no differance between 91 and 87 except the price.

NgoRX8

iTrader: (1)

ehh, ill stay with 91.

EyeBall Fixer...(o)(x)

OK, OK!
How do we know that we're even getting 91 at the pump???
Might be the "honest" guys filling the underground tanks are pumping 87 octane into ALL
the containers...

Welcome to the club.

soldano

i'm in fl and always fill the 8 w/ 93 octane. other ppl can use whatever floats their boat, but for the small difference in price i'd rather follow the directions and have peace of mind.

Vertigo-1

iTrader: (3)

It's worth noting that if pumps at your locations are required to add ethanol...that ethanol in itself has a higher octane than regular gas. Not sure if gas makers blend it in a way to equal exactly the octane they're shooting for though or if we're actually getting a bit more than what's stated because of the added ethanol. I do know though that ever since the local pumps here started mixing in 10% ethanol, my 8 has been able to use 89 very effectively, whereas before, it would noticeably bog down at high RPMs using it. And I only fill up with Shell.

JeRKy 8 Owner

Here's a better question for you:

Is the $2 more you spend every week for higher octane gas really going to break your bank?

If so, then explain what prompted you to purchase a thirty thousand dollar sports car?

alnielsen

iTrader: (4)

There is a difference in gasoline. The price difference you pay between the convienence store and the name brand pumps is detergents. These detergents keep your fuel injectors clean and help reduce carbon buildup in the engine. The same can be said between regular and premium grades. With premium, you get more than octane, you get more detergent in the fuel.
My old RX7's seemed to run slightly better with regular fuel. With this new car I all most allways use premium, as recommended by Mazda.

Paul_in_DC

I tried 89 octane. My car ping'ed all the time. Now it's 93 all the way.

tiggerlee

I 've always use 93. Except for when I drove back to Illinois last year. Can't get 93 in some places along the way so I opted for 89 instead. Car didn't seem to run as good.

mysql101

The price difference is about 30 cents, which is $4.20 per week (assuming a fillup every week).

With that said, perhaps you should read some of the replies more carefully. This isn't just a price issue. Come back and post some more when you understand what octane is and does.

mysql101

Ethanol increases octane, but lowers the energy content. General rule of thumb is to use the LOWEST octane your car can run on. Until you're going FI, most RX-8's will run nicely on 87.

rxeightr

Having over 42,000 miles in mine, I used at least 91 octane for the first 10K miles.

The last 32K miles have been 87 Shell. That is ~ $290.00 difference over using 91 octane.

But as mentioned above, I am not doing it for the cost savings. My RX-8 just runs better on 87.

Winning 8

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

http://auto.howstuffworks.com/question90.htm

Nodoz

it's $3.18 more to fill up from empty to full on premium gas instead of regular. THAT'S IT!!!!

if you are too cheap to pay an extra $3.18 to get better performance and NOT RUN THE RISK OF ******* UP YOUR ENGINE, then maybe you shouldn't have bought this car.

mysql101

Nodoz, thanks for perpetuating yet another urban legend.

91 is recommended, not required (Since every car is different, and people drive at different elevations, they err on the level that fits all). 91 tends to have less power, not more (depends on the blend). Unless your car needs it (high compression) you may as well wipe your *** with the $3.

mysql101

I give this 30 mins before someone else says people are being cheap by using 87.

*rolls eyes*

Wish people would learn how to read. Or at least read the previous posts before running their mouth.

Raptor75

Because of the long slim combustion chamber rotaries run better on the faster burning lower octane fuels. Run as low as you can with out knocks.

yiksing

If your engine is tuned for X octane, putting in X+Y octane assuming that Y is a positive number. The engine would not make more power. If however you put Z octane in where Z<X, your engine would retard the timing to prevent engine damage.