I've had my yellow about 2 weeks now. First tank was 93 ( mobil ), went about 230 miles. I've grannied it to death. 80% highway ( 65 mph ) 20% city. Decided to try 87 ( good 87 chevron ) and see what the diffrence was. I'm now to just over 1/8 of a tank and so far I'm pushing 310 miles ( also a good 70% city and 30% highway ). It also feels MUCH stronger than it did on 93.

just my 2 cents. I'm going to try 93 again and see what happens.

 

I always use 94 Octane gas, and once I filled up 91 and the car was undrivable!
it was so sluggish, and the engine wasnt as quiet.


I'm sticking with 94.

 

I used 93 for the first 3 months and then tried 89 for two tanks. I didn't notice much in mpg (all city) but the car did feel sluggish and as if it was struggling to go fast. I switched back to 93.

 

I have engine/performance problems every time I drop below 91-octane. I'm using 89 right now, but only because gas is so expensive. I've done test drives comparing the various octanes. No difference in mileage. There was a thread a while back where someone noted that it makes little to no scientific sense why you would see any vast improvement in gas mileage by switching to a lower octane fuel. I tend to agree. Also look out for engine knocking and rough idling when using below 91-octane gas.

 

We must be driving totally different cars... 87 octane here, and I don't experience any problem of this sort whatsoever. Car does not feel sluggish compared to running on 91 octane either.

 

just observations, not trying to prove anything. could just be that the engine is settling in and sealing up. could also be that the gas that was in there was the same gas that the car was shipped here with 2 years ago, and now it's getting cleaned out.

 

Perhaps so. However, it's well-documented among several other 8 owners here that at least many of us have experienced engine knocking, rough idling and sluggish acceleration with 87 octane. At the very least, I can definitely attest to the engine knocking (at high rpms for me) because I was able to recreate the problem for my dealer when I first experienced it and they were able to diagnose it as so.

To chime in with you, though, there are others who use 87 and don't have any problems. Not sure why there is a discepancy. Perhaps it's the luck of the draw.

 

Screw that, I still hold my grounds that it only costs an extra three bucks to fill the tank on the good stuff. Three bucks for peace of mind as far as I'm concerned.

 

I usually put 91 in just to keep my engine safe, i generally get about 220 per tank on 91. When i put in 87 i get about 260 miles per tank, but i only do that about once a month. I don't really floor it that much so i don't notice a performance difference hehe

 

...more conflicting data... , sigh...

 

i dont think saving a couple of dollars(expecially between 89 and 91) is worth the engine problems.... as you stated when dropping below 91 octance....

i could attest if you switch to 87 from 93 or 94... but not 89-91... its not worth it imo...

 

Just a pet peve of mine, and I'm probably going to get flamed, but oh well. If you can't afford the gas that the car requires, then you shouldn't get the car. You're gonna pay 25k to 35k for a sportscar then go cheap on the gas. If you want fuel economy, buy a prius. This car is not a grocery getter in any way, don't try to make it one.


Also wanted to add a side note: Spoke with my mechanic and he said that if you granny the car you'll have problems. This car was designed to be taken up into the high-rpms. Not sure what problems you will have, but he said that he's had a couple 8's towed in to him for that very reason. My guess would be engine flooding. He told me that the people that drive the 8 like it's supposed to be never have a problem.

 

Agree with that in general, but Aseras is still breaking his in, so "grannying" it is exactly what he should be doing right now.

Bill

 

I HATE the Prius argument. I mean, no I don't want to maximize gas mileage. I just don't want horrible mileage that I didn't expect. So many people make the argument that if you get a sports car, you have to put up with mileage. This is an exaggeration of course but it's almost like people are saying if the car is advertised at 20 miles per gallon and only gets 5 miles per gallon, then put up with it. It's a sports car. If you don't like it, get a Prius or a Civic. I've also seen "don't get a 30K car if you can't afford to buy premium gas and get 15mpg". :-/

If you notice, most people complaining about gas mileage aren't complaining that it's lower than the average car. We all got the 8 knowing it's an "18/24" car, which is lower than sedans. The people with gas mileage problems are complaining because for them the gas mileage they get is significantly lower than 18/24. (Personally I get like 15/21 grandmaing it which is bad but not that bad). Another guy on this board gets 12mpg grandma'ing it and he had his dealer drive it for a tank and the dealer also got 12mpg. If you want to say that getting 12mpg is fine and to get a Prius if he can't afford getting 12mpg... sheesh.

The other thing that's annoying is the huge range of mpgs people get here. Some get 18 city driving spiritedly. Some get 12mpg grannying it. On a side note, one thing I noticed is throwing in some "spirited" driving doesn't really affect my gas mileage much. Kinda strange.

 

Interesting ... about the inconcistencies in gas mileage; What has the dealerships said about it for those of you that have taken it to them??

Yes, Granny the car to break it in, but afterwards don't be afraid to strech it's legs once in awhile, otherwise you get carbon deposits in the combustion chamber that can give you occational starting problems untill you clear them with an "italian tune up" (a really nice high RPM run)
BTW the owners manual recomends high octane premium gas for the 8

 

I wish I had 93 around my house. Every gas station I go to only has 91 octane.
What gas stations are you guys going to?

 

Wow ... we just had this SAME EXACT discussion last week on octane!

I don't think that the dealerships say very much on the mileage issue because Mazda themselves haven't really come out on a limb to address it. Mind you the car is rated 14-18mpg city (or something like that), so yes, there is variation with each car. I think that we tend to hear more on the mileage issue here because who is going to say "SWEET! I get average mileage".

Regarding the octane, I think that the brands of gasoline that you buy also matter. Shell 87 octane is LIKELY different from Uncle Bubba's Discount Gas-o-line 87 Octane. If the fuel is inferior, it will likely pre-detonate and cause knocking. So *perhaps* those of you that tried the 87 or 89 Octane and found trouble, were actually using something rated lower. And those using 87 w/o problems are fortunate to have a high quality fuel. Oh the other thing is that in winterized gas there is ethanol which will decrease performance.

The other factor on mpg is driving style. If you are in bumper to bumper stop and go traffic where you end up idling more than you drive then you are going to drink gas like a madman.

Oh BTW WhiteDealershipRice, Mazda also says that 87-93 Octane is acceptable. Heck they also say to shift into 3rd at 30km/h ... something like 200rpm .. ha ha.

 

Since we are talking mileage, here is what I got from my new (2004) red RX.

My car had just over 2,000 miles on it when I relocated to LA in California last month. The trip from Fort Worth was a hair under 1,400 miles total.

I fueled up with 89 octane and averaged 23.94 mpg. This at a steady 75mph. I manged 311 miles on one tank of fuel, but I was sweating about it as I rolled into El Paso.

Now, as I drive around LA in the traffic I am getting around 14.5-16 mpg depending on how often and hard I accelerate.

No matter what. I truly love this car. My sister owns a 350Z so we have traded several times. The engine response on the 350z almost seems sedate compared to the RX-8! Mind you, the engine makes incredible power when you stick your boot to it, but it certainly doesn't feel faster or more powerful than the RX-8. One thing I noticed was how the 350 engine felt like it had a heavy flywheel. RPM were slow to rise and slow to fall. My sister felt the opposite on my RX. I much prefer the sharp response of the RX!

Anyway, I'm sticking with 89 octane for now. The engine runs like a top, gets good gas mileage on the highway and I've never flooded it even if just running the car out of the garage to wash it. (I follow the user manual and shut down after running the rpm up to 3,000 for a few seconds before turning the ignition off).

 

bingo.. i was a bit more aggressive after the 700 mile mark, i've started letting it go to 6-7k every now and then. so on my second tank ( the 87 ) i was actually driving it a bit hard, plus it was stop and go. which really amazed me that the mileage increased so dramtically.

 

I'ved tried 91, 89, and 87 now in the car and am patiently waiting to either blow the doors off a vette or have the engine rattle and fall out the bottom and have gotten neither. I've heard people discuss "knocking" but to date haven't heard of anyone actually say they got knocking. What's a rotory "knock" sound like? My engine rasps loudly since it was new, the idle is always rough, the tranny screams, and I love it all!

 

I used lower than 93 once and my car sounded absolutely horrible--it varies from car to car. So I only use 93.

 

Wow, each of us gets a really different car...like they're all hand made or something. The guy who built my engine must have had a little hangover compared to the guy who gets 18MPG. I get 15-16 in the city (worse when I give it the "Italian tune up") and when I use lower octane gas, it kind of "clatters" quietly, which could be a rotary knock. It also drives a little sluggishly with the junky gas.
I think the original post "First 2 tanks of gas.. big diffrence in mileage with 87 v 93" was seeing big differences because of the break-in period. But I'm goign to try a tank of 87 just for the heck of it.

 

Strangely, not necessarily true. I had the highest mpg ever (23) on the fill-up after being stuck in a 100 mile back-up.

I find that the single greatest influence on the mpg is not octane, not speed, not high rpm shifting... It is the number of engine start/warmup cycles. These run super rich when cold (and even partially cold). Want to improve your mileage, follow the old epa advice, plan your trips. If you start the car in the AM and run an errand, start it again at noon and run another errand and then again at dinner time you will use more gas than if you ran the same errands (same total mileage, same number of restarts) all in a row. Too lazy to go out to the garage right now to look at the log, but I have done this and the difference has been 10%. That's the difference between 20 and 18 mpg.

Now don't flame me because I am not overly concerned with gas mileage, I just keep very accurate records as a result of my relationship with the IRS.

 

The engines are hand assembled.

 

Hand assembled, not hand made. There should not be much variation from engine to engine as a result of hand assembly, the pieces all fit together the same way.