Poor Gas Mileage, getting worse and worse

clownshoes2

2017 CX-5 GT No Tech
:
CX-5
I know this has been discussed before but here we go again. 2017 AWD CX-5, GT no tech package. 100k Kms on the odo.

My gas mileage has been getting steadily worse and worse. I currently sit at about 10-10.1 L/100kms. Previously I'd get somewhere between 9 and 9.5.

Is there some sort of magic phrase I can say at the dealer for them to take me seriously? The dealer literally just shrugs and says "it's the shitty canadian gas".

Do I just use the Seafoam stuff and hope I don't blow my motor?

Any and all help appreciated.
 
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Mazda CX-9 Signature
That converts to about 23mpg which sounds about right for awd city driving. What were you averaging before? Did you check aligning? Air pressure? Change in driving route? More passengers?
 

clownshoes2

2017 CX-5 GT No Tech
:
CX-5
That converts to about 23mpg which sounds about right for awd city driving. What were you averaging before? Did you check aligning? Air pressure? Change in driving route? More passengers?
We drive mainly highway, minimal city driving. I was averaging about 9-9.5 L/100kms, sometimes in the 8's. I check tire pressures often, same routes, same passengers. Nothing changes. Same gas station even (Costco).
Have you changed the plugs yet? That can make a difference.
No I have not. It only has 100k Kms on it. Still a while for plugs yet.
 
:
CX5 GT
0.5l/100km is not a large deviation. I dont see any major problems with that.
Change spark plugs and air filter and call it a day or try different fuel.
 
:
2019 CX5 Reserve AWD
That converts to about 23mpg which sounds about right for awd city driving. What were you averaging before? Did you check aligning? Air pressure? Change in driving route? More passengers?
I get about the same in mostly suburban driving. Maybe a few tenths of a mile more.
 

sm1ke

Work In Progress..
Moderator
Contributor
:
Canada
:
'18 CX-9 Signature
I would check the engine air filter, Manual says it should be changed every 56k kms or 3 years, but it's possible that even with a recent change it somehow got gunked up or clogged. If the engine air filter and intake piping is clean, I would go ahead and change the plugs ahead of schedule. I changed mine recently and my fuel economy seems to have improved by .5 - 1.0 L/100km, but mine was also due for a change at 64k kms (I'm at 72k now). You can also try a fuel injector cleaner, they're fairly cheap and readily available.
 

clownshoes2

2017 CX-5 GT No Tech
:
CX-5
I would check the engine air filter, Manual says it should be changed every 56k kms or 3 years, but it's possible that even with a recent change it somehow got gunked up or clogged. If the engine air filter and intake piping is clean, I would go ahead and change the plugs ahead of schedule. I changed mine recently and my fuel economy seems to have improved by .5 - 1.0 L/100km, but mine was also due for a change at 64k kms (I'm at 72k now). You can also try a fuel injector cleaner, they're fairly cheap and readily available.
I change my air filter every 25k just to be safe. Every few months I run a tank of 94 octane with fuel injector cleaner. I go WOT once in a while to "blow out the carbon". I do everything I'm supposed to do. I just don't want to lunch my motor doing the fuel system thing through the vacuum system.
 

sm1ke

Work In Progress..
Moderator
Contributor
:
Canada
:
'18 CX-9 Signature
I change my air filter every 25k just to be safe. Every few months I run a tank of 94 octane with fuel injector cleaner. I go WOT once in a while to "blow out the carbon". I do everything I'm supposed to do. I just don't want to lunch my motor doing the fuel system thing through the vacuum system.

In that case, I'd swap out the plugs. If that doesn't improve mileage, I would try a Seafoam treatment. I don't think there's much else you can do to improve mileage outside of maybe reducing the weight of the car or increasing tire pressure a few PSI.
 

HardRightEdg

US 2020 CX-5 Touring AWD Soul Red
You might try two treatments with Techron fuel system cleaner. I did that recently on a high mileage Sienna and have seen an increase of 0.5 - 1.0 MPG in comparable driving.
 
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'16.5 CX-5 AWD
Seafoam is great for cleaning carburetors.

The only in tank cleaner I've found to work is Red line SI-1 Fuel System Cleaner. It is easy to get through Amazon at about $US14.50 a bottle.

Since Skyactive engines use direct injection, it has less effect, since it rarely touches the intake valves. I used STP Intake Valve Cleaner on mine at 60k miles and got a little more than 10% less fuel consumption. I used 2 cans and followed the instructions. I just repeated that at 90k with little or no change, so I'd say a can every 50k kms after one good cleaning will be good.
 

Natey

Moderator
Contributor
Patron
Just asking because that's a pretty common reason for your mileage per gallon to change for the worse.
Cheap and easy to replace!