Poor gas mileage, questionable coil pack, oil on spark plugs...

AVC

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'17 CX-5 Select
Yeah, the A/C isn't causing this. If the A/C compressor were bound up by bearings or whatever, the idle would would be highly erratic.

And, likely the transmission fluid condition isn't doing this, either, as it shifts decently.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
Aren't all modern cars required to throw a code if there's something wrong that affects emissions ( most fuel or ignition problems, etc)?

If the long tow seemed to cause the problem I've heard that transmissions can suffer from towing.
What was the drive like? Does the transmission fluid have a strange smell or taste?
 
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2018 CX-5 Sport
Do you drive with a lead foot? Take off fast from starts, and speed?
Do you go on short trips? The CX-5 gets very bad mpg when it is cold, and if you go on short trips the mpg suffers.
 
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2018 CX5
If I had this problem what I would do is find a top tier gas station (like Costco) which has the best amount of detergents, fill it up a few times, make sure my tire pressure is 1-2 PSI above the suggested range, put in a new air filter, and see what happens. If you don't get back to your 30 MPG, have a trusted mechanic take a look.
 
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2017 Mazda CX-5 Touring
I ran the car with no A/C yesterday and it seemed to coast significantly better and highway mileage improved to ~25 still not the 30 I used to get but its a step in the right direction.
Ok. That suggests that your A/C clutch bearings are bad. The next thing I would do is to check the A/C pulley bearings by removing the belt and turning the pulley by hand.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
Yrwei52 has discovered that most ATs are underfilled at the factory. I still wonder why the MPG dropped after that 700 mile towing event and suspect it could be related to the AT, but maybe it was a bad tank of gas.

I apparently got some really bad gas once and I could tell a year later. I use 91% iso (red heet is the same) as I've read it is most effective for removing water.
 
Aren't all modern cars required to throw a code if there's something wrong that affects emissions ( most fuel or ignition problems, etc)?

If the long tow seemed to cause the problem I've heard that transmissions can suffer from towing.
What was the drive like? Does the transmission fluid have a strange smell or taste?
well I dont want to taste it... but ill give it a whiff. it should throw a code but it might just have tuned itself to run rich as a result of the constant throttle usage
 

Chris_Top_Her

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San Antonio, Texas
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'15 CX-5 Miata AWD
Have you ever added fuel system cleaner to the fuel tank (regular maintenance). Used a head cleaner, and also your driving style can play into excessive oiling of you drive light footed all the time. Electric tape is used from factory to bundle wires so unless it looks janky it's probably oem. If you are worried about LTFTs you can unplug the battery to reset them
 
Here's what I was towing for 700+ miles which is why i think it may be a trans issue
 

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Chris_Top_Her

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Moderator
Contributor
:
San Antonio, Texas
:
'15 CX-5 Miata AWD
Trans isn't causing extra oil blowby.. you are operating your engine at increased load at lower rpms than typical.. therefore higher cylinder pressure and more blowby (especially with "fleet mpg" MPG 20w oil if you use it). Not surpirsing, but not really an issue either. Use a cleaner to get that crap out before it becomes deposits on your piston/spark plugs.
 
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2017 Mazda 6 Sport
you're still under the powertrain warranty so have the dealer look at it. Mention the mileage drop and the oil you see, but DO NOT tell them about towing the boat unless they ask. How much does that trailer weigh? The tow capacity is only 2,000 pounds
 
and the whole car was loaded, and the boat cabin was full... I was moving.

Wow I'd have to imagine it was over 2k pounds towing the boat+ everything else in the car and inside the boat! And over 700 miles! That likely was way to much strain.

Mazda builds their cars on the edge, example the rear differential is tiny and takes a scant amount of fluid to cut down on drivetrain loses......they do not over engineer their cars with tons of leeway to add HP mods or in your case towing capabilities.

As others stated run some cleaner through engine. I'd suggest replacing the diff fluid and looking into some driveline parasitic loses occurring.....

who knows maybe there is something screwed up with the AWD logic and its sending tq to the rear wheels full time....that would kill the gas mileage since the CX5 is primarily a FWD bias system.
 
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2013 Mazda CX-5 Sport FWD Auto
That was a heavy boat, car filled to the brim, stuff on roof. I don’t think it would greatly diminish your mileage but I’m worried the transmission fluid is cooked. No fluid is lifetime after a workout like that. My ‘19 RAV4 says to change the transmission fluid at 60k under severe service (and I think it says to leave alone otherwise). 700 miles with that strain and I’d want to drain and fill the trans 3x as you’re approaching 50k. That was beyond severe. I’ll echo another sentiment: have a dealership check it out and don’t mention the 700 mile trek.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
My dad was into sailing. First a 19' Chrysler, then a Cat22 ... a J24. When he turned 80 they sold their lake place and donated the boat. But he couldn't let it go and some guy sold him a Cat 25 and delivered it to a slip he found at a nearby lake. But we found nobody wanted to try and tow it because it had a fixed keel and rode almost 15ft high. He had to get some guy with a bulldozer to take it from the storage place down to the boat ramp every season.

A good thing he enjoyed painting because that's how he spent most of his time with it.

I'm more apt to put a kayak on my roof than tow a trailer but it still adds drag. I know how it is moving stuff. And sometimes you have to. But from now on I'm going go with a U-Box or similar if at all possible.
 

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