Wierd Gas Mileage Issue

[New2Mazda]

I've had a 2007 Mazda 3 GT Hatch for 2 years now (got used).

I've put about 120,000KM on it and got it at 50,000KM.

Since I've owned I filled it with Petro Canada Gas regular.
I normally get 8.3-8.5L/100km consistently and about 650-700km on a tank (my commute takes me up a lot of hills)

I use Canadian Tire Full Synthetic in the gold jug 5W-20 since I owned the car and PureOne Purolator Oil filters since I owned the car.

I'm running Dunlop Sport summer tires which are about 6 months old.

I just got the brakes and rotors (Raybestos advanced tech rotors and ceramic pads) replaced at my local repair shop which I've taken my cars to for about 4 years and never had a problem. They also replaced the oil and filter.

I just cleaned the K&N air filter and re-oiled it. Double checked its install correctly.

I noticed on the last tank (first since oil change, rotors and pads, air filter cleaning) I'm going to get as far as the computer can tell about 575km to this tank or about 75KM less then I normally do. The L/100km has risen to 8.8 and I reset right after the rotor/breaks were replaced.

I noticed that the car feels much much heavier since the new rotors were put on and the reseller says the shipping weight for each rotor is 18lbs.

I take trips with car all the time with 150+ pound passenger and the mileage has always stayed the same.

I replaced the coolant at 90000km and the spark plugs at 120,000km and I have 170,000km on the car now.

Any suggestions, things to check or try would be appreciated. My local mechanic doesn't have all the electronic diagnostics equipment a Mazda dealership has and I'd like to avoid paying Mazda prices to look at this.

I have an OBD unit if that can be of any help.

Any info would be appreciated.

The only additional not is the guy that put my summer tires on filled them to 35PSI and the door sticker says 32PSI in case that matters.

[sol_searchin]

Since you noticed this after the brake install I would look for brake drag.

[jwangyue]

Is there any sound/noise that was not there before, you many need to have someone drive the car and you stand outside and listen.

[gotak]

As someone said about brake drag. Also, consider going back to a paper filter. People like those K&N but they really do nothing for the car but with the risk of more dirt entering the engine and the oil coming off and gumming up your mass airflow sensor. If your MAF is dirty it messes up the engine computer and can easily also be the cause of your increased fuel consumption.

[New2Mazda]

I'm game to clean the MAF can you link me to pictures or instructions?

[Chester_Lampwick]

You might want to check wheel alignment. Maybe check your tires for uneven wear.

[DualSoul]

I'm game to clean the MAF can you link me to pictures or instructions?

Google is useful at times like these (http://lmgtfy.com/?q=clean+maf)...

[Cab0oze]

I'm game to clean the MAF can you link me to pictures or instructions?
Link to some instructions i wrote a long time ago (http://www.fordfusionclub.com/index.php?topic=165030.msg3501043#msg3501043). Some pics are broken now, but you shouldn't need em.

...and as others said, brake drag is very likely. After going for a drive on the highway and no hard stops, pull off/stop and cautiously touch your rotors. They should all be slightly warm from your last stop. If one is hotter than the others, then you have excessive drag.

Also, when cleaning your air filter, make sure that you let the thing dry 100%. I rushed it too much once, and the oil locked the moisture in. Mine was so bad that the car kept stalling after starting, but if you were in a rush like I was, you may have made a similar mistake but to a lesser extent. Just something to think about.

[-|CHECKMATE2012|-]

Wait isn't 7.4 or 7.5 decent gas miliage for city driving? Is that 28 city or so?

[New2Mazda]

MPG = 28 or 8.5L / 100km

I'm getting about 9L /100km now or 26MPG now.

.5L * (50000/100) * $1.30 = $325 a year. So I know it seems like its minimal, however I really don't want to pay $300 plus a year more every year.

[New2Mazda]

Update:

I had the brakes inspected by a different Mechanic and they say there is nothing wrong with them, they are not dragging and that the first mechanic did an excellent job.

I also go a computerized alignment but things were not out by that much. I got a new tank of gas from a different city and things seem to be back to 8.3L/100km for the first 100km on the tank.

Thanks for all the posts, I'll let you know the result at the end of the tank.

[Chester_Lampwick]

Man, 50,000 kms a year. Better you than me. My total mileage between two cars and two drivers is half that. I know why that extra 0.5 l/100km means so much to you.

[New2Mazda]

Weird with this last tank I'm getting 8.3l\100km and my KMs on tank is back to 700km.

I same gas station so I think was a case of bad fuel for a few tanks or problems with their new pumps.

[machx]

2006 GT and ATM, and I'm filling my tank and getting just shy of 500km. I use Petro and Shell regular....

You're getting 850km?!

[Fuyuzora]

I'm thinking the blip may have simply been as a result of the heatwave?

Either way, interested to hear what the cause turns out to be.