Saving fuel?
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Saving fuel?
I'm not too bothered about saving fuel. I care more about the fun I have whilst driving BUT I read somewhere that RX8s use less fuel from 3000-5000 than they do from 1000-3000.
Has anyone heard of this?
Is this true at all?
If so, why?
Does anyone have any fuel saving tips for motorway driving?
Has anyone heard of this?
Is this true at all?
If so, why?
Does anyone have any fuel saving tips for motorway driving?
I'm not too bothered about saving fuel. I care more about the fun I have whilst driving BUT I read somewhere that RX8s use less fuel from 3000-5000 than they do from 1000-3000.
Has anyone heard of this?
Is this true at all?
If so, why?
Does anyone have any fuel saving tips for motorway driving?
Has anyone heard of this?
Is this true at all?
If so, why?
Does anyone have any fuel saving tips for motorway driving?
i havnt cared enough to look it up before. If you want to save gas dont start the car and take a bike.
It's a matter of efficiency. An engine is most efficient at the same point that it produces the most torque.
You have the increasing effort to push through the air as speeds go up of course, but going too low is just outside the ideal efficiency point for the engine.
https://www.rx8club.com/rx-8-discuss...rx-8-a-233937/
You have the increasing effort to push through the air as speeds go up of course, but going too low is just outside the ideal efficiency point for the engine.
https://www.rx8club.com/rx-8-discuss...rx-8-a-233937/
Your driving habits:
(Driving to get good mileage will not impact your warranty)
I have personally seen 24mpg in my RX-8 when it was healthy. Smooth throttle usage is the most important trait, and to hit that it was basically "no throttle usage". Steady state speed for hours on end. Frankly, it's rather boring. My mileage drops as the speeds go up, and as I get frisky and wanting fun. This is true for you as well. If you are serious about saving gas on the highway, set cruise control to 65mph and leave it there, dodge all the traffic pounding down your *** in the rear view mirror, and assuming everything about your car is healthy and the road is flat, you will be able to hit 23-24mpg. Bump that to 70mph, and it's probably going to drop to 22. 75mph gets about 20, and 80mph drops it to 18-19. Air resistance is unavoidable. But it is also something you can mitigate a little bit. AC on and windows up is better mileage than AC off and windows down, unless you are staying under ~40-50mph, when it starts to swing the other direction.
(Driving to get good mileage will not impact your warranty)
I have personally seen 24mpg in my RX-8 when it was healthy. Smooth throttle usage is the most important trait, and to hit that it was basically "no throttle usage". Steady state speed for hours on end. Frankly, it's rather boring. My mileage drops as the speeds go up, and as I get frisky and wanting fun. This is true for you as well. If you are serious about saving gas on the highway, set cruise control to 65mph and leave it there, dodge all the traffic pounding down your *** in the rear view mirror, and assuming everything about your car is healthy and the road is flat, you will be able to hit 23-24mpg. Bump that to 70mph, and it's probably going to drop to 22. 75mph gets about 20, and 80mph drops it to 18-19. Air resistance is unavoidable. But it is also something you can mitigate a little bit. AC on and windows up is better mileage than AC off and windows down, unless you are staying under ~40-50mph, when it starts to swing the other direction.
at 90 with the a/c on I got 13 miles a gallon but also was in stop and go traffic on the interstate for almost an hour and a half... I was sad that I got that bad of gas mileage. Otherwise I get about 18-19 going 80-85. I can get 21-22 going no faster than 70.
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Joined: Aug 2012
Posts: 39
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From: England
It's a matter of efficiency. An engine is most efficient at the same point that it produces the most torque.
You have the increasing effort to push through the air as speeds go up of course, but going too low is just outside the ideal efficiency point for the engine.
https://www.rx8club.com/rx-8-discuss...rx-8-a-233937/
You have the increasing effort to push through the air as speeds go up of course, but going too low is just outside the ideal efficiency point for the engine.
https://www.rx8club.com/rx-8-discuss...rx-8-a-233937/
If the most efficient point of the engine is at the highest point of torque... If the RX8 has 156lb ft at 5,500rpm... Does that mean the most economic RPM to 'cruise' at would be 5,500rpm?
Has anyone actually tested this?
There are so many factors in play 
For the engine, and just the engine, yes it runs most efficiently at 5,500rpm. However, assuming that you have a 6sp MT, this puts you at 110mph in 6th. And you are losing massive efficiency due to having to push through the air. You also have an increasing amount of heat and drivetrain losses as the rpm increases, which start offsetting the peak engine efficiency point as well.
Just like 5,500 in 3rd is 55mph, but it's worse mileage than upshifting to 5th, or even better up to 6th, at 55mph. But on a pure "only considering the engine", yes 5,500 is more efficient combustion than anywhere else. It ends up being a net loss though, however it's not nearly the loss of mileage that piston powered cars see that have their torque peaks down low.
If you look at the dyno charts for modern cars you will often see a torque bump at the RPM that the car sits at in it's highest gear at 60mph. It's part of what helps them get highway mileage ratings, tuning the intake and exhaust manifolds for efficiency right there, and the torque improves as a result.
For the engine, and just the engine, yes it runs most efficiently at 5,500rpm. However, assuming that you have a 6sp MT, this puts you at 110mph in 6th. And you are losing massive efficiency due to having to push through the air. You also have an increasing amount of heat and drivetrain losses as the rpm increases, which start offsetting the peak engine efficiency point as well.
Just like 5,500 in 3rd is 55mph, but it's worse mileage than upshifting to 5th, or even better up to 6th, at 55mph. But on a pure "only considering the engine", yes 5,500 is more efficient combustion than anywhere else. It ends up being a net loss though, however it's not nearly the loss of mileage that piston powered cars see that have their torque peaks down low.
If you look at the dyno charts for modern cars you will often see a torque bump at the RPM that the car sits at in it's highest gear at 60mph. It's part of what helps them get highway mileage ratings, tuning the intake and exhaust manifolds for efficiency right there, and the torque improves as a result.
My personal experience, (from watching afs) keep it under 75 and 4k rpms. If you go above either the ecu starts dumping fuel into the engine.
At 70mph I stay at 14.7 for the most part. At 80mph 14.2ish. 65mph seems to be the sweet spot for my engine to get max mpgs.
At 70mph I stay at 14.7 for the most part. At 80mph 14.2ish. 65mph seems to be the sweet spot for my engine to get max mpgs.
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