the PCM being stuck in a closed loop makes alot of sense actually

maybe have mazda flash it, complain about MPG and performance (even tho its fine) and theyll take a look on the house

 

Well, here's my .2 worth. I live in N/E OH. Historically, my mileage has dropped by only 2-3 MPG the past two winters (18-19ish to 16). (Not true so far this winter though. I'm still at 18 and not complaining!). And that's with the low temps combined w/ the winter grade fuel. U are in a total different situation w/ temp and fuel formula.

I doubt the problem is the thermostat. The computer would catch the constant low coolant temp and throw a CEL. IMO, there's something wrong w/ the car. I'd take it right back to the dealer (I wouldn't let on that UR using syn oil though). Question: do U ever rev it? Not saying that's the issue but I and several other members feel that U should hit redline fairly regularly. I hit redline at least once a day, several times if the weather allows. Good luck. Let us know what U find out.

 

Have you ever look at your Air Filter?? Dirty Air filter means more Fuel to use. Just my two cents.

 

dirty air filter means restricted air flow, which decreases fuel consumption, and results in a reduction in performance

 

Well all of a sudden I got 250miles out of my tank again.. for.. 4 tanks.. and now I'm back to 150 per tank O.o

I've checked practically everything suggested, there was nothing dirty, clogged, or otherwise..

I'll have to taker her in next week

 

you went through 5 tanks of gas in 3 days?

 

It's the gas.
Gas with more Ethanol gets less mileage.

 

Yep.

And I doubt it's ethanol, my dad gets gas from the same station and he hasn't noticed any mileage difference with his SUV

 

Can you think of any reason you might have gotten more, did anything change, did you change anything? Drive around any overweight people? Carry any more work stuff? Temperature in your area change? less traffic?

P.S. How many miles are on your car as of right now?

 

I'm at 6,000 something.

I haven't changed anything at all in the way I drive, temperatures have been steady for the past week or so (including when I was still getting 150miles).

I only drive myself and I only weigh about 150lbs. Nothing in the trunk or passenger seats, just me.

Haven't made any part swaps or cleaning or anything.

Traffic has actually been heavier due to construction.

 

Same gas station too?

 

Yep, I always get my gas at Sam's Club, and it's always 93 octane

 

Would you know?
Many gas stations will put 87 octane in the 89 octane pump and 89 (or even 87) in the 93 octane pump.
I recently found this out because I gassed up and got 27 Mpg at a station next door to a weekly Classic Car Show. It turns out, there are people with old restored cars, who instantly know 93 from 87 octane and will turn around and drive back to the station.

 

Huh.. How would I tell the difference apart from an mpg difference?

 

sorry maybe i am just thick this morning but i do not understand this post

 

^ i had to read it 2x also.. not quite sure.

 

my two cents are on the ignition system somewhere.

(trailing ig. disconnected/faulty)

 

Recently my MPG has dropped significantly as well. I usually average 220-235 a tank. Right now I'm at 70 miles on my trip at 1/2 tank and had a full tank. That can't be good... Can the winter gas really make that much difference, or should I take it in?

 

I think I've figured it out, my oil level has been above the max

 

just becasue ur oil is above will not cause it to use more gas....maybe smoke some but not burn more gas....the gas gets injected in the intake manifod seperate from the oil.....

 

Hmm.. then I don't know, dealership couldn't find anything wrong

 

wow that is crazy

 

wow, thats odd... i get 200-220 to a tank, but since it has been colder recently i have been getting like 240

 

You shouldn't be seeing a 50% decrease in fuel efficiency, unless everything possible is wrong at the same time. My mileage decreases on winter gas too, but 1-2 mpg max. You may want to try a tank of mid-grade gas and see what happens, since me and some other owners get better fuel economy out of lower grades and I haven't seen a hit in performance.

 

this is weird and this is the first time i've heard of this issue. just changed to new plugs last week and new coils this weekend. followed all instructions on replacing these.
but now i noticed a definite drop in my gas mileage. used to be around 18-20mpg and now it's like 14mpg. nothing changed in driving style, distance and highway/city drive percentage. is it possible that one of the things i replaced could be faulty? does anyone have an idea which one it might be? i'm going to observe it further and see if there's any change and then do an inspection this weekend.

i've always heard rotorheads getting improved mileage or smoother-running engine after new plugs and coils. seems like mine got more thirsty

i might put the old coils back in and if that doesn't work then i'll inspect the plugs. just hoping someone might have an educated advice that would lead straight to the problem. thanks!

PS
i've thought of other factors like temperature (it's f***in hot here now), oil, or simply just bad gas (last fill-up at costco)