Hi,

Has anyone else run into this ? My CX 5 has 8,000 miles on it and it keep going down 1/10th of MPG's- 32.5, 32.4, 32.3 I am not worried about the actual miles dropping just why? It has been warmer here then say January and it was higher.. Also pretty much the same gas stations.

THANKS !

 

Are those mpgs actually calculated, or just the digital readings? There is no normal vehicle reason for the decrease - if there is a decrease. Seasonal increases in ambient temps usually mean a slight change in mpg (every thing else equal, which they almost never are) but not always. The temperature of the gas you pump changes, gasoline expands as it heats up so pumping the same volume of fuel in the summer means slightly less weight of fuel than in winter - you get less actual fuel for the same cost. It is the weight of fuel which runs the engine, not the volume. The result of this can be a slight decrease in mpg as the weather warms, on the order of what the OP is seeing.

But in truth the changes the OP notes are so small that they may not be real. They may be slight changes in the amount of gas pumped due to pump shut off, different pumps, etc. IMO nothing to worry about.

 

LOL wow... really? They are so small amounts what the heck are you looking for perfection. Maybe you are part of the BORG collective! You start to be concern with drop in MPG at the 2-3mpg drop over an average of several fill up from at least 1/2 tank of fuel.

 

What kind of fuel are you putting in your tank ? When you have Ethanol in the fuel, your mpg suffers. Even 15% lowers fuel economy . Summer blend , Winter blend ?https://www.yellowpages.com/virginia...l-gas-stations

 

I only use Chevron 91 octane in daily driving .I even try to use the same station and pump. LOL
I did say daily driving not anything spiritedly driving.
But it is California formula, so I am very aware of the changing values all the time. My point was that seeing a drop in MPG from the op in such small amounts and not really posting much information is well withing normal amounts that can vary with something even like the temperature of the tarmac.... LOL Not kidding
I should add since day one of new owner ship of my Mazda I have complete gas use and mount's written and comparing my pen to paper math calculation with what the MPG in Mazda indicates. I also list any service changes psi in tires, spark plug changes oil and filter service ect.
I think if you look I posted my handbook somewhere a couple of times on this forum.

 

Oh I don't care about the actual miles per gallon, I just had never owned a car that drops by tenths when my habits have not changed. My last car when this happened it ended up with a check engine light..

 

Honestly I use pretty much everything - Mobil, Sunoco - Delta sonic when I am in NY... It all seems to run the same no matter what I use.

 

My other vehicle is a 2023 Jeep Grand Cherokee L so I know about low MPG's ! The Mazda is like a gas saver

 

Be happy for now. I've never gotten over 28mpg and I drive conservatively with very little city driving and using non-ethanol or premium E10. I've been very disappointed in this. That said, at least it's not creeping down like yours. I hope it's just leveling out.

 

Well this just about answers you original question.... ALL those companies use different formula. This can and does effect the MPG in anything you use! The formula less proprietary ingredients can be found in the US Federal Government certifications of fuel sold in retail in the USA!

And while you may "think" your engine runs the same on all them it doesn't!!!!! The first thing the ECU corrects is timing and fueling. You can easily see this by use of a scan tool connected to the diagnostic connector and doing a live DATA stream and comparing when you either mix different fuels (brands) or completely run different fuels.