This may be more of a pipe dream than anything, but I do a decent amount of long drives in my MX5, and the fuel efficiency certainly isn’t great. I realise I could just get a car that is more efficient, but I like having the MX5 at my end destination, so I am looking for any creative suggestions or solutions to make the car more efficient for longer drives. I don’t want to do anything that will permanently change the car, but I would be happy to switch parts, etc. I have looked at aftermarket tuning software, but they are obviously marketed more towards making additional power.
Check water temperature is correct when cruising; thermostat condition can affect fuel economy.
Check tyre pressures. (But then you always do that before a long run?)
Check air cleaner is nice and clean.
Check the wheel hub temperatures for brakes sticking a bit, a warmer wheel is wasting petrol!
Close the windows and put top up! (But then why have a convertible?)
Anticipate when to slow down so as to lift off the throttle earlier, and therefore waste less energy in the brakes.
Carry minimum weight in the car.
Keep the car clean for a more slippery airflow, especially underneath if recently near a mud bath…
The list is endless, but with increasing triviality the returns diminish…
EDIT
The exhaust pipe can also give some clues. I always used V-Power for a fraction more miles/penny, but a noticeably cleaner exhaust.
This was my 2008 Niseko in 2023 after 35K, and averaging 37mpg for my mostly weekend and two-up holiday trips 18K mileage
I have the ND 1.5 Sport, and on a decent run from Dartford Bridge to South Yorkshire, 70mph as much on cruise control as possible, achieved 58mpg. General average is around 54mpg.
As a comparison my older NC 2.0 Sport delivered 40 and 34mpg respectively.
I have never been too worried with the ND’s consumption.
Use this as your excuse to buy an ND, if you’d like one. Realistically the true cost of changing to or acquiring another car will almost certainly eliminate any savings from increased efficiency, at least for a very long time.
What mpg do you typically see? Might be worth checking it’s in line with that seen by other NC owners doing similar types of driving.
Air resistance is proportional to the square of the velocity, so if your trips are motorway/dual carriageway, typically sat at 70mph, cut it to 55-60mph and watch the improvement. Will take a bit longer of course to reach your destination, which of course is important if your life’s exciting (or you could leave earlier). If not exciting, and the 70mph speed is to get back before Doctors comes on TV, then the 55-60mph will give good returns.
Modern AC systems really don’t increase fuel consumption at all significantly, but I would love to see this tested in an mx5!
Definitely higher psi in the tyres will help. The type of tyre used can also help significantly.
Ultimately, the above suggestion of decreasing speed is going to be the most effective! Apart from decreasing drag (take off any splitters, spoilers, anything that adds downforce) you can not realistically increase efficiency on the motorway without slowing down, because it’s the most fuel efficient route to take in the first place most of the time.
Have a proper full remap and it does give increased fuel economy when on a long run.
You can have it done also for standard or super fuels, (changing the map settings via the steering wheel).
(Have other stuff, but it’s the map that does it).
Mine was done specifically for cruising and when on the power etc etc.
Just averaged 40-42 mpg on the motorway in Spain recently.
That was at 70 mph,(ish).
I doubt you will achieve anything more without doing so.
3.75 Sport Tech.
As all mentioned decent servicing and brakes checked (not binding) tyre pressure correct then it’s all down to the driver, road conditions and speed.
Expect on a long run approaching 40mpg in an NC1, a little more in the NC2 (I’ve owned both) road speed important. If you stick to 70mph where possible it’s gonna use more fuel, 60 to 65mph will be the sweet spot I’ve found to get a decent mpg.
If you aren’t getting anything like the above figures keeping the speed down then you have the wrong car for the job, or just suck it up and have a blast.
Take some speed round roundabouts if its safe to do. More speed on the other side means less speed will need to be gained to reach cursing speed. Also its fun.
I notice a 5mpg improvement when I put the standard MX-5 hardtop on. Of course, it would take about 50k miles to pay for itself but if you liked the hard tops for other reason it might help?
All the suggestions are good and may help. I get well over 50 mpg in my ND RF on long motorway runs (not exceeding 70). The only additional suggestion from me is keep the overall weight down (incl fuel only for expected drive time to each scheduled stop (plus limited contingency). If it’s a regular route plan where to do top ups at reasonable price at 2 hr intervals.
While all the good advise above will help a little, your cars mpg is what it is. If you want a significant change you will have to change model to an ND.
Our last (mk2.5 1.8) MX5 never got better than about 42 mpg, (and I am a fairly steady driver), our current (mk4 1.5) has averaged 53mpg (overall, actual).
The thing that makes the greatest difference to mpg is the air temperature which drops it by 3 mpg in the colder weather, and I am not sure you can do a lot about that!!
I’d start with checking tyre pressures and drop your cursing speed a little (65mph on motorways/dual carriageways is probably the sweet spot as has already been said). I would get to around 38mpg on a run from my old NC2 doing this - I was never able to break into the low 40s with mine. My current ND1 1.5 has managed 58mpg doing the same route…
Also important is anticipation and to use the brakes as little as possible. It was brought up as a suggestion around roundabouts already, but use the same thinking in the approach to all hazards. Lifting off the throttle and allowing the car to settle to an appropriate speed without using the brakes. Known as ‘Acceleration Sense’ in Roadcraft
With consideration of a remap, just bear in mind that if you’re only considering it for economy reasons, the cost of the remap would buy you a fair amount of fuel! It would take you a long time to recoup a 10% fuel saving as an example, when you’ve spent say £300-500 on the remap.
Overall, just enjoy the car! For me, employing a few Advanced Driving techniques is about the satisfaction of the drive, with an improvement on journey MPG being a nice bonus. Mine is used spiritedly and my usual overall tank MPG is around 45mpg for the ND, which I’m more than happy with. Similar use with my NC2 was circa 33mpg.
Fascinating! Cold weather causes a reduction in mpg? Cold intake temperature should increase the efficiency, and oil temperatures should be much the same when warmed up, so it seems that the MX-5 ECU is not well mapped for low temperatures? I guess I am missing something.
Overall, I rarely get out of low 30’s on my NC1 2litre
My mpg charts for my old 1.4SE Astra on ten years of commuting the identical journey round the M25 show it. I retired in 2005, so that’s the end of regular driving
Several factors, mostly longer warm-up time from a cold system, heater in the car, demist, headlights, slower traffic with more stop-start, etc
I am no scientist but my limited understanding is ICEs need more fuel to create a bigger bang in cold temps when the air is more dense and so ICEs are more powerful in cold temps.
When the air is less dense ICE’s not need so much fuel to burn and the fuel burns more cleanly.
As a result of the need to burn more fuel ICE’s are less efficient in colder temps.
