Miata MPGs? Or how to be a cheap bastard on my commute?

Just moved back to San Diego have about a 75mile a day commute (round trip) with taking kids to school, going to work, going home. It's almost all interstate and often with traffic.

We spent the last year and a half in Seattle where I was able to carpool/use public transportation and speed limits were lower so I got myself a very nice 2003 Mitsubishi Montero. Its a great rig, holds the two car seats well, has plenty of storage is comfy and can go anywhere. (Ive got 1yr old and 4yr old so one rear one forward facing and since I drop off and mom picks up we cant just have one carseat friendly car)

I've calculated/observed even with gas prices where they are now we spend about 430 dollars a month on gas 300 of which is the montero which is a premium recommended vehicle that seems to get around 15-16 on average with this commute.

The other family car is a minivan which does better on the highway but in stop and go/commuting ends up around the similar 15-18mpg.

My other personal vehicle is my autocross toy the 1990 Mazda Miata. It's only ever gotten about 25mpg for me but I don't have a hardtop and I think it needs an 02 sensor, with a hardtop and a tuneup could I see a bit better mileage?

The Montero is REALLY nice and in fantastic shape but selling it will definitely take a loss over what I bought it for and obviously any sort of car payment will likely outweigh any savings on fuel.

So is using the Miata for my commute a plausible way to save some money and maybe even get the wife to ok spending a little bit more on it for things like a hard top? Would I/H/E open up the motor a bit and see any other improvements?

I am getting some autoX wheels/tires soon so could put some more econo tires maybe a bit taller on the Daisies? I noticed weight of the wheel/tire combo seems to play a bit part of overall economy with my TDI jetta however (which I sold when we bought the montero)

IME - mind you, I've only owned four Miatas so far - you'll be hard pressed to get much more than 28mpg out of a Miata. Maybe 30 if you're really lucky. Doesn't matter if it has a hardtop or not. They're just not very good on fuel for their size.

I was always impressed with my 100k mile (essentially stock) 1992 Miata. My fuel economy almost always fell within the 27mpg-33mpg range, depending on weather, traffic, and terrain. Never really fell below that regardless of commute conditions. As that would suggest, the overall average was probably ~30mpg. Since the hardtop is essentially the same shape, just a little smoother, I doubt it's good for all that much improvement. Sounds like a bit of a tune up is in order though.

Check out www.ecomodder.com

Tallest and most narrow all season tires you can fit/find, with at least 40psi in them, synthetic differential (75w90) and trans fluid, factory alignment, make sure brakes are releasing correctly (lube sliders). Hardtop probably isn't worth much, especially at lower (under 55) speeds, doubly so as it probably weighs more than the soft top.

Driving technique comes into play too, brakes turn gasoline into heat, and you get 0mpg at a stop, the less you are on the brakes or stopped, the better.

I was able to get 30mpg pretty consistently in the warm weather with my two Miatas. When on the freeway, there's no benefit to driving like a maniac.

My commute was 35 miles one way, about 30 of that on a 70mph freeway, where I did between 70-80.

I've had 4 Miatas as well, and I had a hard time getting them to do UNDER 30mpg, but I guess it depends on your exact mix of city, highway, traffic, etc... My commute was 25 miles each way, but it was a lot of open country roads, with some traffic/stop lights. Every tank was a very consistent 33mpg. I think the best tank I ever got was 38mpg and the worst was maybe 31. I also didn't beat on mine all that hard when it came to acceleration. I was more interested in it's cornering ability.

My NC Miata fuel mileage was worse...31mpg was normal, 27 on the low end, 34 on the high.

Klayfish wrote: I've had 4 Miatas as well, and I had a hard time getting them to do UNDER 30mpg, but I guess it depends on your exact mix of city, highway, traffic, etc...

This was my experience with my '90. I typically got 30-35mpg commuting at average speed of 40mph.

My miata has all the I/H/E stuff but given a 5 mile each way commute at fairly low speeds and lots of stops my mileage is usually a spectacular 20. Twice what the burban gets but hardly economical.

My 96 averaged 30. My 2008 averages 29.

I saw a big jump in mileage when I replaced the front wheel bearings. At least that's what I accredit it to. I still don't know if I believe it or not. I get 31-33 mpg with many hard accelerations and frequent trips to 6-7k rpm. 28 miles one way to work (mostly 55 mph) and then buzzing around town some. '91 1.6L manual.

EDIT: Min 91 octane with no ethanol

Heheheheh, the Manic Miata gets about the same fuel economy as my '67 Le Mans did - somewhere around 13 MPG. That's not its fault, though.

99 Miata, hardtop, stock, 80mph highway commute with FL E10 fuels, consistent 25-26mpg. Didn't notice a difference without the hardtop. Our 2007 Civic EX gets 33-35 under same conditions. 2005 Saab 9-2X (WRX) gets 24-25 same conditions, but on premium.

25mpg doesn't seem unreasonable for a 50/50 split out of a mostly stock Miata.

My anecdotes:

2004 Mazdaspeed Miata: FM catalog, Blouch upgraded turbo, stock soft top, Haltech EMS, 31-33mpg all highway. 28mpg combined.

2000 Miata: 5spd/4.3 combo, hardtop, i/h/e, 31mpg highway. Didn't get enough city to get a measurement on it.

1995 Miata: Built motor, 2554r turbo kit, Megasquirt DIYPNP, hardtop. Best highway tank of 35.3mpg, typically around 30-31mpg combined, usually 33mpg highway.

Bear in mind that the turbo cars drink 93.

Getting a nice lean cruise will give huge benefits, but will probably take quite awhile to pay for the engine management system. I'd just do a tune up and roll.

Isn't there a 5th gear swap using RX-7 parts?

Driver and model of your miata are huge factors, my 99am does right around 78 mph at 4k rpm in 6th gear, on a road trip I averaged 29 mpg with the a/c on and the top up, I'm sure with the a/c off or a lower cruising speed that number would improve but my around town driving tends to average only about 24 mpg.

In reply to Gearheadotaku:

You can get the 5th gear set from an 86-91 NA RX7 and swap it into the Miata tranny. I did the swap a few years ago. Here is a write up http://forum.miata.net/vb/showthread.php?t=441727&page=2

Yes there is a 5th gear swap, and you can swap in different rear ends (with drivshaft and axles) if you have a 1.6 (4.3:1) to a 1.8 (4.1:1) or 6 speed 3.6x:1 (cant remember exactly). My 1.6 used to get 27 no matter how I drove. Now my commute is 20-40 miles a day strictly 75-80mph and I get an astonishing, for me, 31mpg. I have narrow stock sized tires and its lowered with new fluids in the trans and diff those are the only mpg enhancing things ive got. I dont drive like an ecomodder either

That's a tough one. The old Miata isn't really a mileage champ. I never got 30s.

$300 a month on gas is quite a bit but doesn't quite amount to the cost of a purchased new replacement. At least not at today's $3 a gallon average in CA. If / when it starts going back up after the Russia and other political issues change, that could change.

An 03 Montero doesn't fetch a lot of money on the used market 2-6 seem to be the range on the SD craigslist right now.

At the same time, it would be easier to sell a not-so-fuel-efficient-Montero-like vehicle when gas is cheap.

I'd leave the Miata alone and use it as a fun car when you have time for it but start considering replacing the Montero over the next year or two since you seem rather fond of it. The Mazda6 and CX5 would make a fine replacement. Even finer if you sign up for a Mazda Motorsports account and submit your autox results whereupon you can get a Mazda at cost w/ their S plan deal.

Ultimately, you need a more fuel efficient daddy car.

The hardtop very definitely does make a difference at freeway speeds. I used to do regular runs up and down the 401 in Ontario. It's fairly flat and straight with the only traffic around Toronto. Over a 6 hour trip you can get a very good idea of what works from a fuel economy standpoint. The hardtop made an appreciable difference over the soft top. The Spec Miata guys know that their cars are faster on the straights with them as well, there's another data point.

O2 sensor is a given. You'll always get the best economy out of a car that's in good mechanical shape, but since a failing O2 sensor usually leads to the car running very rich, that one's particularly important.

I wouldn't run taller tires than stock - for one, it will affect your aero - but I would run a relatively narrow and efficient one. No 165s or anything, but a 185 or 195 would be all you need.

Get a front air dam, it'll help. Looks good, too. Smaller mirrors will also make a difference. But the biggest thing you can do is driving style. Think of your fuel as delta-v - changing speed will burn more of it. If you can keep your head up enough to maintain a consistent speed, you'll use less fuel. As a happy coincidence, it's less frustrating, more interesting and safer!

I don't think I've ever seen over 30 in either of my Miatas. 25 mixed sounds reasonable. My '94 is only rated at 19/25.

http://www.fueleconomy.gov/feg/Find.do?action=sbs&id=10639

1100+ Miata owners on fuelly. Averages seem to be mid 20s for tha NAs. http://www.fuelly.com/car/mazda/mx-5_miata

You may take a loss on selling the Montero, but buying a vehicle of equal value that doesn't get E36 M3ty mileage will make a difference very quickly. There are plenty of cars out there that meet your needs that would get double the mileage, on regular.

I'm in san diego and have been comuting in my 90 on 205/15 star specs and last tank was 29.5mpg. I average about 70 on the freeway doing 25 miles each way with about 3 miles through stop lights. Best I've seen was 32.1 when I went to LA last month and I usually see around 30. No hard top / top down half the time.

I think the biggest difference you will notice is putting 25 bucks in the miata instead of $xx in the suv.

I got better MPG on secondary roads than I did on the highway. 55 on 35mph country road is a lot easier than 65mph on a 65mph highway.

I think the best I got was 27 in my 1990 1.6l, usually it was around 22-24mpg.

The montero was my long time lust for land cruiser but cheaper/more reliable/better mileage for camping/off roading with the family. It's only just hit 100,000 miles and is the 20th anniversary in mint condition super nice leather interior,super clean. I bought it for 9k about 1.5yrs ago and it has a lot of records etc. I really like everything about it except for mileage and I am not even sure the 300 bucks a month is a "big deal" I just happen to also have the miata which is going to stay aligned for autocross and be primarily a fun car. If my fun car also can do some commute duty and save gas cool.

I've debated getting rid of both and getting a daddy duty/fun car like a Focus ST or GTI but car payment will end up costing more than the insurance on both cars+the montero gas still.

The closest thing to a replacement for the montero I have been considering atm is actually a volt because then I can almost eliminate using gas and can use carpool lane.

My commute is oceanside to mira mesa so its almost all freeway but I don't really do over 70

Your car sounds like mine ouchx100 so I must have something else eating at my mileage. I don't do over 70 and I have 195 star specs on daisies

$300 would be a big deal to me. Invested, that's > $20K in just 5 years.