53 MPG tank in 1990 Mazda Miata: personal best (4.5 L/100 km)

[MetroMPG]

( * OK, 52.7 MPG US = 4.5 L / 100 km... but who's counting?)

Filled the MPGiata yesterday for a new best tank for the car!

It's always a bit of a surprise when I calculate the tank MPG, because the MPGuino rarely lasts an entire trip without resetting, so it doesn't save accurate tank data.

I was extra surprised this time because it included a couple of longer trips where the car wasn't at its optimal weight or shape (see above pic).




Mods in place for this tank:
(in no particular order)

- MPGuino fuel economy computer
- 50 PSI
- zero-toe alignment
- cleaned & regapped spark plugs (the gap was 0.010 wider than spec!)
- air conditioning delete (removed components)
- power steering delete (belt removed)
- ignition timing advance
- air dam, with...
- partial grille block
- half size radiator, and...
- one of two factory cooling fans deleted
- smooth wheel discs
- taller gearing (larger diameter rear wheels/tires)
- side mirrors delete/relocated inside
- LRR tires on the front, narrower than stock: 165/65R14 Dunlop Enasave
- wiper delete
- synthetic motor oil: 66% 5w30 + 33% 10w30
- weight reduction (goal: 100 lbs / 45 kg is attainable)
- MAF / open loop AFR adjustment
- synthetic lighter weight transmission oil (50% lightweight GM Syncromesh + synth 75w90)
- synthetic differential oil
- WAI - warm air intake
- reduced disc brake drag (serviced calipers/sliders this year)
- tonneau cover

Details of these mods in the build thread: "MPGiata" modding thread: aiming for 50 MPG with a 1990 Miata


Driving style/environment:

In a word: optimal.

One of the reasons I'm able to get such stellar fuel economy from all my cars is because I'm lucky to live in a part of the world with pretty laid-back drivers and nearly empty scenic rural roads that I usually use instead of the freeways. And I rarely have to drive in busy city traffic.

Almost all the driving for this tank was on MPG-optimal scenic/rural roads, with a max limit of 80 km/h / 50 mph or below. Conditions: warm, dry, and not a lot of wind. Techniques: driving with load on hills, when it doesn't hold up following traffic. Engine off approaching most stops/turns. Maximizing conservation of momentum in curves, because that's so much fun in this car!


Needs more!

It needs more mods: Coolant/transmission heater, springs on the brake pads, lower coil springs, belly pan, rear fender skirts/rocker extensions... I probably won't do anything more to it this year, but with some of these additional tweaks, it seems like a 55+ MPG tank (4.3 L/100 km) is a realistic goal for next year.

[euromodder]

No bad reaction to higher tyre pressures ?

The latest MX-5 doesn't particularly like higher pressure in the tyres

[MetroMPG]

Looser fillings in the teeth, maybe.

[airbiteses]

I did not know that there are such tires 165 / 64R14 ... But the factory for this model was 165 / 60R14. The weight of this car with a driver of 950 kg. 0-100km / h 7.8 s (0-62mph), what cars would have to have 200 hp to have such a time.

[MetroMPG]

My mistake - typo! Dunlop Enasaves are size 165/65 R14. From a Mitsubishi Mirage (Space Star).

The factory tire size for this car here was 185/60 R14

[Daox]

Very impressive Darin!

[MetroMPG]

Thanks.


What's cool is there's more where that came from... once I do a few more mods.



So I can either increase my MPG a bit more, or up my average speed and keep the MPG where it is. (2nd option is what I'll probably do. I'd like to be able to hold 50 mpg US @ 50 mph on level ground, and it's not quite there yet.)

[skyking]

Nice going!!!

[MetroMPG]

Thanks. We've passed the peak, though! Colder weather has the current tank sitting at ~47.

I'll be putting it away for the winter soon.

[aerohead]

Originally Posted by MetroMPG

Thanks. We've passed the peak, though! Colder weather has the current tank sitting at ~47.

I'll be putting it away for the winter soon.

Maybe that 53 will tide you over 'til spring.Great goin'!