I did a search for this topic and found a thread but frankly did not see any knowledgable answers. Someone was telling me that the RX-8 needs to be reved high to keep the engine clean. And that if you shift too low crap will accumulate in the engine. Any opinions?
If your priority is keeping the engine in good shape for many many years, and your priority is not driving like you stole it, at what rpm for each gear is a good shifting point?

 

5-7k is good with a run to the beep a few times aweek in first and/or second

 

Shift at 3-4k if you are conserving gas. Shift 5-6k for normal driving, and redline it if you're having fun

 

I'll try to not be long-winded.
I do business with Mazda Remanufacturing, supplying the plastic shipping containers for their front wheel drive automatics and the RX8 engine. Nanner, nanner, I had an RX8 engine in my shop, a year before they came to market!!
Anyway, the main guy for engine rebuilding tells me that if you use 93 octane, shift it where you want. If you use 89 octane, keep the RPM up around 4500 before shifting. It's all about the oil injection for seal lubrication. The oil mixes and burns better with high test.
HE also said that they have many RX7 engines back for rebuild with these nasty rubber-like ***** all inside them and totalled housing walls from synthetic oil that did not burn. They DO NOT KNOW which synthetics burn properly for use in this engine and HE suggests using NO SYNTHETIC OILS! HE's not saying that none are okay, just that he (or Mazda) do not know which are suitable or not.

 

Good advice.. the service manager advised thusly: if Mazda had intended that the Renesis use synthetic, the manual would say so, or at least suggest it as an option. I double-checked with the RX certified mechanics who confirmed this, emphatically.

 

Did he happen to say anything about 87 octane (R+M/2)? If not, could you please ask him next time you chat with him.

Thanks,
rx8cited

 

To maximize mpg, shift at 2k rpm, i.e., keep the revs under 2k. The car will not bog and is driveable. To maximize the fun value, shift at the buzzer and keep the revs high. There's alot of room in between those limits to suit the individual driver, IMHO.

 

Also, you can always buy 87 gas. I've used several tankfulls in my 20k miles and am still uncertain as to the results. Currently I buy premuim from costco and am happy.

 

I actually heard it's more fuel effcient when driven at higher rpms (like 4-5k as opposed to 2-3k). Can anyone confirm this?

 

I disagree, and I think almost everyone else will. The secondary fuel injectors come online at 3750 rpm. You're putting more gas in the engine that way. It is usually more fuel efficient to run at the lowest possible RPM for that speed. Running 70 mph at 3500 rpm in 6th saves more fuel than 70 mph at 4200 rom in 5th.

If you're just cruising, steady speed, flat road, you should easily be able to drive at 2500 - 3000 rpm without hurting your engine. It may not be run, but it will save gas.

 

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Doubtfull it is more efficient but a hell of a lot more fun. I really wouldn't worry to much about your engine becoming dirty from shifting to early, as long as you rev it up once in a while when the engine is warm. Like many people have said, shift at the right conditions, i.e. if its wet and slippery don't shift were you have the most torque and are likely to slip the tires and event though it sounds and feels great there really isn't a need to drive around town at 9K in first gear. When I'm driving normally I generally shift between 3.5K to 5K. Just my thoughts.

 

Since I purchased my car (last week), I've had two fill-ups with 92 octane. Most of my driving consisted of 90% freeway/10% city. In that time frame, I've driven 600 miles...I hit up to redline at least once a day, and I don't shift until I'm near 4-5k. My normal cruising speed on the freeway is between 70-80mph @ 4k on 6th gear.

I calculated my mpg and it turned out to be 18-19mpg.

I'm going to limit one of my drives to where I'll shift at 2-3k just to see the gas consumption difference.

 

If the purpose is to conserve, the above information is important. I was told the secondary injectors fire at 3600 but either way you can see the point - stick to primary for conserving.

 

Good post Kwullen. I agree with rx8cited. We need to know what he says about shift points with 87 octane. Many have reported better fuel mileage using 87 compared to 91. Should we not shift below 4500 rpm using less than 91?

 

i find shifting at 2k pretty tough, even if you can do it and you want to save gas you'll probably shift at 2k for like a day at most after that day you realize you bought the car cause of the way it feels and how it almost begs for you to pick up your ***** like you have a pair and step on it then you start driving like a maniac again. I gave up of the quest of great mpg...

 

That's exactly what I've come to conclude. And when I drive like I want to I'm still getting over 17 or 18 anyways so it's not too much difference from my 18.5 average. I wish it was higher but that's just what it is.

I shift anywhere from around 3000-8000 . I haven't heard the beep yet. Normally I probably shift around 4-6.

 

Wow. People shift at 2k rpm?!

 

the rx-8 being my first manual car also my first car i also sometimes have hard time shifting.

 

I got 19.8 mpg on one tank at avg speed of 90 mph to vegas (from the grand canyon) last week. fun and good mpg at the same time .. I was so happy.

most times i cant get 13 mpg in town ..

now that my baby is broken in a bit. 3000 miles. it does get better mog in the city now. I am around 16 mpg with normal rx8 driving. i.e. i dont baby it . My tach lives at 8500 ..

so its getting better, and if i drove it like a granny then i think it will do more like 17-18 mpg in the city.

 

I agree wholeheartedly, though I did a whole tank shifting around 3500. It's almost like the talking foocus commercials..., as I walk up to it I can hear her begging to be ridden hard! heh :D

 

Shifting between 4000 and 7000 rpm 90% of the time.
Shifting between 7000 and 9000 rpm 5% of the time.
Shifting below 4000 rpm 5% of the time.
Just my driving style. Everyone's different.

Low rpms are probably detrimental to the engine. Constantly at redline probably detrimental as well. I could be wrong. I bet most manufacturers design their cars for real world driving and the best results are in that range.

Even if the engine did not bog at low rpms, it's probably better to run the car at higher rpms. You know the old saying, use it or lose it.

 

Sorry guys, I should have included that part of the conversation.
He says there is no problem with running 87 octane, however, it tends to carbon the combustion chamber and you will need to run a tankful of 93 octane through it at least every five tanksful. I ran the cost savings numbers and decided to just run 89 octane. I have not found a fuel consumption improvement with 87 octane, but I only ran two tanksful (is that a word?) of it and was more interested in the racers claim that it gives the best HP. If it does, it's not enough to measure with the seat of your pants.
I ran a Stillen 300ZX yesterday on a road near my home. We had about a half mile straight leading into a windy section, about another half mile. He pulled me about one car length on the straight but I outbraked the bejeezus out of him before the first corner and after stopping on the next straight to wait for him, I turned around to find him in the ditch after the first left hander. He was okay but tore up the right front fender in the heavy brush off the road! He said he was going right down to the Mazda dealer to test drive an RX8!! He couldn't believe how fast I left him in the turns and didn't realize the speed difference he'd have to use! He said he got in trouble in the first two right handers and couldn't get it back together in time to brake for the sharper left hander. I didn't tell him I do it faster when alone and didn't want anyone to get hurt trying to keep up.
Ooops!

 

That's not true, when I kept it under 3500 rpms during my first 1500 miles of break-in I was getting an incredible 22-23 mpg combined city/highway. Now I shift about 3500-4500 and I get about 19-20 combined. Shifting lower yields way better gas mileage and also partial throttle acceleration helps too.

 

I mainly shift at as close to the recommended speeds in my manual as possible which seems to start with higher RPMs and get lower the more you go up.

They are approximately:

2nd: 14 mph - 3250 RPM
3rd: 22 mph - 3000 RPM
4th: 29 mph - 2750 RPM
5th: 36 mph - 2750 RPM
6th: 46 - 2500 RPM

I don't do this constantly but I'd say 85% of the time I do. I don't bog down either.