MX5 MK3.5 - driving for efficiency

[Blofse]

Hello everyone, I have been looking for this information but I have been struggling to find. I have a 2.0 sport tech and was wondering what the best way was to max the mpg in terms of what speed in which gear.

So with the mx5, is it better to set the rpm lower or higher to max in each gear?
What about which speed I should be travelling with which gear (6 speed GB)?
Currently I am getting about 31mpg with normal unleaded, good synthetic oil, good tires but slow town driving mostly. Average speed around 40 as I do a motorway drive on a daily basis.

For my old car, it had a nice diagram in the back with curved gears/speed and efficiency ratings. So it was good to drive up to 30mpg in 3rd, then was optimum to switch to 4th around 35. It was a diesel engine so it typically liked low revs and less turbo. With a naturally aspirated car I am not sure what's best.

Thanks for reading - cheers.

[watchnut]

As a fellow MX 5 owner (be it a MK3) 2.0l , I don't tend to worry too much about economy as this car for me is a "fun" car.

However I do like to beat the tax man and not chuck too much money at him in the fuel dept.

Holding a gear too long when going up will use more fuel

Braking late and heavy uses more fuel ....as you have had the right foot down too long

Try lifting on the gas pedal as soon as you see brake lights in front of you rather than hitting your brake....this will require a bigger distance between you and the car in front.

Don't just watch the rear of the car in front of you.....look at what the vehicles in front of him are doing....too the limit of your vision and anticipate when they may start slowing so you can start slowing with less pressure on your gas pedal.

An "eco" driver always has options....
1 keeping foot on gas
2 less gas
3 lift off gas
4 brake.....this will make you more of a "proactive driver" rather than a "reactive" driver....ie one who has no option but to "brake"

This will also all require good mirror work knowing how close the vehicle is behind you so that you can also "control" him for example if he is right up your arse then lifting off too quickly and braking could result in a rear end shunt.....where as very gently on the brake pedal will make him "react" to your lights, yet keeping momentum for yourself

When coming to junctions especially roundabouts which tend to be "open" junctions, look early at the traffic on the roundabout, also at what is coming from your right about to enter from your right that you may have to give way to, try to time entry without having to stop......1st gear from a standing start uses a shed load of fuel.... if you are rolling in second.....you will use far less

I have done hundreds of eco driving courses as a trainer, using some of the tips above could save you more than 10% on your fuel consumption, most of my customers on average achieve far more, as my average saving is 23%........most people hold gears too long, drive too close to the vehicle in front, brake heavy and late, and are not trying to anticipate what may happen ahead.....stop starting is expensive on fuel, takes longer for a journey, lowers your average speed and increases time spent on the journey, and uses more fuel

try it and see.....maybe you will get 40 mpg or more? I often do

Do NOT try "neutral" coasting.....it can be dangerous if "engine" braking is required.....it also does not save fuel as the car is still using fuel to keep the engine running, where as engine braking on modern cars the fuel supply is cut off and the engine is continuing to run from the residue of the fuel already pumped in and the wheels rotating keep it cranking

cheers

[RussNC]

Let it get warm and then up to 7k - when the fuel gauge gets low, just put some more in! if you want efficiency buy a diesel Mazda 2!

[Blofse]

watchnut said:

As a fellow MX 5 owner (be it a MK3) 2.0l , I don't tend to worry too much about economy as this car for me is a "fun" car.

However I do like to beat the tax man and not chuck too much money at him in the fuel dept.

Holding a gear too long when going up will use more fuel

Braking late and heavy uses more fuel ....as you have had the right foot down too long

Try lifting on the gas pedal as soon as you see brake lights in front of you rather than hitting your brake....this will require a bigger distance between you and the car in front.

Don't just watch the rear of the car in front of you.....look at what the vehicles in front of him are doing....too the limit of your vision and anticipate when they may start slowing so you can start slowing with less pressure on your gas pedal.

An "eco" driver always has options....
1 keeping foot on gas
2 less gas
3 lift off gas
4 brake.....this will make you more of a "proactive driver" rather than a "reactive" driver....ie one who has no option but to "brake"

This will also all require good mirror work knowing how close the vehicle is behind you so that you can also "control" him for example if he is right up your arse then lifting off too quickly and braking could result in a rear end shunt.....where as very gently on the brake pedal will make him "react" to your lights, yet keeping momentum for yourself

When coming to junctions especially roundabouts which tend to be "open" junctions, look early at the traffic on the roundabout, also at what is coming from your right about to enter from your right that you may have to give way to, try to time entry without having to stop......1st gear from a standing start uses a shed load of fuel.... if you are rolling in second.....you will use far less

I have done hundreds of eco driving courses as a trainer, using some of the tips above could save you more than 10% on your fuel consumption, most of my customers on average achieve far more, as my average saving is 23%........most people hold gears too long, drive too close to the vehicle in front, brake heavy and late, and are not trying to anticipate what may happen ahead.....stop starting is expensive on fuel, takes longer for a journey, lowers your average speed and increases time spent on the journey, and uses more fuel

try it and see.....maybe you will get 40 mpg or more? I often do

Do NOT try "neutral" coasting.....it can be dangerous if "engine" braking is required.....it also does not save fuel as the car is still using fuel to keep the engine running, where as engine braking on modern cars the fuel supply is cut off and the engine is continuing to run from the residue of the fuel already pumped in and the wheels rotating keep it cranking

cheers

Thanks for the detail, thats some good information. Though helpful wasn't exactly the reply I was after. Unless your saying low revs in this type of car are always better therefore early shifting is correct? However, in my last car that was defo not the case - that preferred mid revs in each gear. But with the mx5, it might be better to keep each gear above 4k revs for example where I typically sit in the 3k region unless pulling away. So is there any information regarding this?

[Blofse]

RussNC said:

Let it get warm and then up to 7k - when the fuel gauge gets low, just put some more in! if you want efficiency buy a diesel Mazda 2!

Yer that's what I do a lot and hence this post - its costing me a bit too much but its damn fun eh? Still can't believe I own this car, its Amazing fun and it keeps you awake in the morning!

[tr7v8]

Managed 44MPG chasing the Millie Miglia in 2016. Loads of autostrada driving at around 65MPH with cruise on. Several reasons, wife had horrendous sciatica so trying to stay smooth to not shake her about & B. french tanker drivers on strike so trying to stretch a tank full.
On short journey's it isn't great but a lot of that is using all the revs in every gear once warmed up.

[Blofse]

Surely cruise control can't me the most efficient and even if so, I don't know what gear would be best for what speeds. In your example @65 you can be in 3rd-6th, all which create different rev amounts. I guess I'm the only person to have ever bought a sports car and wondered about efficiency he he. I see my mx5 as two cars - one for getting to work (with a bit of fun when any car gets up my are while driving, always nice to see a tiny dot in the distance) and one for weekends where I can drive it properly of county roads. The weekday version could do with a bit more mpg as I'm at 31 even after a service. The cold weather can't help, running the heater etc, but surely I should be getting more than that?

Out of interest, there is a way to reset the mpg meter - can someone remind me how?

[Evoluzione]

I think not only have you bought the wrong car, but you're also in the wrong place for that kind of malarky.
Peak torque on a diesel; 2000rpm? On your car: 5000rpm. How much fuel are you going to be using at 5k?

If your nerdyness goes to such depths I would guess that there will be a place on the internet or a book to find answers and that there is probably an equation whereby the weight, the CD, gear ratio, torque curve and more are all taken into consideration to provide the best RPM to be at for best MPG in each gear.
This has the basics: https://en.wikibooks.org/wiki/Automobile_Repair/Op...

But I think you already know those.

This looks sufficiently dreary for a good bedtime read:
https://www.amazon.co.uk/Fuel-Economy-Vehicles-Pow...

But it's worth a few tanks of fuel

A bit more digging:

https://www.amazon.co.uk/Motor-Vehicle-Economy-Ric...

49p bargain!

I just hope I don't trip over you on the road and look forward to your "How to fit a diesel engine in my MX5 thread"

[Blofse]

I guess I appreciate the sarcasm and the real message of your message there, pistonheads isn't the place to ask this. Also I appreciate that this place is where you ask how to max things out as opposed to go smoothly. If I see you on the road though, I'll still try and have some fun!
One of the reasons posting here is quite commonly people will quote they get 40odd mpg, well if they are quoting that - then someone must care about fuel efficiency right?

The only reason I asked is there is very little Mazda specific information in this area - that is all. But it sounds like Mazda know their market - drivers who drive mx5s don't care about that, they care about the max rpm and bhp he he.

Surely you can't all be driving at max speed at all of the time? :-)

[VladD]

I'm not even close to being an expert but I'll give this a go.

An engine burns fuel most efficiently at peak torque, so if you were driving without resistance, primarily wind resistance, your optimal speed would be there, or about 116 mph for a 6 speed MX5 at 5000 rpm. Unfortunately resistance increases exponentially as you get faster, so the gain you get for approaching peak torque is far outweighed by the losses of wind resistance. So what you really need is a graph with two lines. One showing the torque of the engine at road speed and the other showing the resistance force through the air at road speed. Where they cross would be your optimal speed.

This gets further complicated because the air isn't a constant density. Colder air will be harder to push through, so you'd actually need several wind resistance lines based on the air density, which is obviously related to air temperature. Also, engine efficiency is effected by air density and temperature, so you'd need multiple lines there too.

In practical terms, if your car has a MPG calculator that you can reset, I'd find a nice long straight bit of road and drive for a few miles when it's quiet at 40 mph and see what MPG you get. Then repeat for 45, 50, 55 etc. You should then be able to plot a graph of the results and work out where is best.

[Evoluzione]

Blofse said:

I guess I appreciate the sarcasm and the real message of your message there, pistonheads isn't the place to ask this. Also I appreciate that this place is where you ask how to max things out as opposed to go smoothly. If I see you on the road though, I'll still try and have some fun!
One of the reasons posting here is quite commonly people will quote they get 40odd mpg, well if they are quoting that - then someone must care about fuel efficiency right?

The only reason I asked is there is very little Mazda specific information in this area - that is all. But it sounds like Mazda know their market - drivers who drive mx5s don't care about that, they care about the max rpm and bhp he he.

Surely you can't all be driving at max speed at all of the time? :-)

My message is that isn't what it's for, but if you so wish to follow that route there is stuff available to help you, each to his own. I did Google MX5 diesel too
Like many I bought it for fun and not much else, i'm lucky enough that it isn't my daily so this has compounded that effect, I drive it for fun everywhere.

[SmilerFTM]

Blofse said:

I guess I appreciate the sarcasm and the real message of your message there, pistonheads isn't the place to ask this. Also I appreciate that this place is where you ask how to max things out as opposed to go smoothly. If I see you on the road though, I'll still try and have some fun!
One of the reasons posting here is quite commonly people will quote they get 40odd mpg, well if they are quoting that - then someone must care about fuel efficiency right?

The only reason I asked is there is very little Mazda specific information in this area - that is all. But it sounds like Mazda know their market - drivers who drive mx5s don't care about that, they care about the max rpm and bhp he he.

Surely you can't all be driving at max speed at all of the time? :-)

40mpg+ is only done on long runs, I can easily get over 40mpg out of mine on a long run but going to work 12 miles away from home along a mixture of town, B road and dual carriageway sees figures more like 27/28mpg

[tr7v8]

Blofse said:

Surely cruise control can't me the most efficient and even if so, I don't know what gear would be best for what speeds. In your example @65 you can be in 3rd-6th, all which create different rev amounts.
Out of interest, there is a way to reset the mpg meter - can someone remind me how?

Obviously in 6th! why would I do hundreds of miles in anything else? Cruise on the Mazda is the most efficient, also the most relaxing & stops speed "creep".

To reset the MPG reading select it on the rh button then press & hold. I'll reset same as miles trips.

[Blofse]

tr7v8 said:

Obviously in 6th! why would I do hundreds of miles in anything else? Cruise on the Mazda is the most efficient, also the most relaxing & stops speed "creep".

To reset the MPG reading select it on the rh button then press & hold. I'll reset same as miles trips.

Thanks for that, will reset once I can drive again without snow :-)

[Blofse]

SmilerFTM said:

40mpg+ is only done on long runs, I can easily get over 40mpg out of mine on a long run but going to work 12 miles away from home along a mixture of town, B road and dual carriageway sees figures more like 27/28mpg

Ah that makes more sense. The main concern that I was driving the car so badly that I was getting low mpg but by the sounds of it I'm on the high end for city driving.

Thanks for all of your replies and bearing with me, seems I have got enough information to keep me happy :-)

[watchnut]

For the op.... my "energy" saving tips don't reduce driving pleasure, they can help enhance the driving experience especially in your forward planning.

When i give "eco" training for the customers first drive I ask them to drive as they normally drive, they are advised they are not on a test. after a first drive and a debrief on it, i then "coach" them around the same course. They on the whole get around at a faster average speed, lower MPG, and in less time.

You appear to be keen on when to change gear for economy, using science to aid fuel savings, I would suggest that you look for vehicle sympathy for changing up and down gears. Of course we want to have fun....why would you want an MX5 otherwise?.....mine is a toy, and I don't worry about the fuel consumption when I am going on a track day, or a decent A or B road. But, I drive sympathetic to the vehicle as a ragged car don't tend to last long, and neither do we judging by the "5 are killed on average everyday on UK's roads" stat...........just about all are full licence holders, having never taken further training since passing the basic driving test.

I improve my skills as someone who knows he is not the best or can ever be "perfect"......so if you find out how to change up/down getting the most out of every drop of fuel, please advise !.... but please enjoy your "5" as well

regards