I'm getting a 2006 Mazda 6s Sedan( 3.0L V6) and after reading up a bit it gets an average of 20mpg city/highway. I mainly drive regular streets but do Highway driving about 40% of the time. I make around $100 per week and I'm fine on cash right now, but once I start driving this thing I'm going to be spending alot more on gas than my previous car( a 1999 Corolla.) So how can I go about upgrading the fuel economy of this thing?

 

Not much you can do except keep a little extra air pressure in the tires and your foot off the accelerator pedal as much as possible. Some may suggest adding an exhaust or a CAI, but neither of those things have ever been scientifically proven to increase fuel economy in a modern fuel injected engine (in fact, they can often reduce fuel economy).

 

drive 5 under the speed limit on the highway, accelerate slowly in the city, keep the tires up to pressure, don't carry loads that you don't need, use appropriate gas (no premium if regular is recommended and vice versa), and keep your maintenance up to date.

the last one is really important. if you keep up with scheduled maintenance, your engine will stay up to par on power. if your engine has to work past a clogged fuel filter, old oil, etc., it will under-perform and tax the engine to the point where you will lose major economy.

 

Once again you and I will have to disagree on the clogged air filter thing. I still maintain that the only possible affect a clogged air filter can have on fuel economy is a slight increase in economy. I've started a new thread in the question here: https://www.mazdaforum.com/forum/general-tech-6/does-clean-air-filter-improve-fuel-economy-24588/

 

i never said clogged air filter. i said clogged fuel filter. i don't, however, believe that a clogged air filter will increase or decrease mpg. the engine management is going to increase or decrease fuel based on air input. a clogged air filter will just adjust the amount of air coming in. you could make the argument that it will cause you to accelerate slower, but i don't really buy that either. it's not what you drive, but how you drive it. that's all that it comes down to.

 

Sorry, my bad. I guess I'm remembering a different discussion.

Regarding the clogged fuel filter; I have a few comments given how the fuel systems work in cars today:

• The pump typically does its thing at full-tilt-boogie all of the time with the excess fuel simply being returned to the gas tank
• Most cars these days comes with a fuel filter that will typically last the lifetime of the vehicle (roughly a quarter of a million miles); barring of course buying lots of contaminated fuel.
• My guess is that even if the fuel filter was beginning to clog (but not yet to the point of causing drivability issues), there would be zero reduction in fuel economy.

My thoughts on the oil filter are similar in nature; pumping oil through a clean filter element versus pumping oil past a clogged oil filter with some or even all of the oil going through the bypass valve makes zero difference in the fuel efficiency of the engine.

 

the difference in the fuel system is that it is designed to run on a pre determined fuel pressure all the time. a perfect example of this is my dads truck. it is designed to run at 60 psi. the first time that the pump went out, it was at 59 psi and wouldn't run. after some calling around to idiots at different parts houses (who all said it was fine 1 psi low), we finally called an actual mechanic who said the system will not run at 59 or 62psi. the operating range is for 60 to 61 psi.

I will definitely grant that the modern engine can and will overcome fuel system issues more easily than older systems could have, but they are still designed to operate under specific parameters. one of which being fuel level. the quarter tank rule is for pump cooling and to keep sediment in the tank out of the pump.

the oil thing is altogether different. the strain on the pump wouldn't tax the engine. the thing that taxes the engine is the engine not getting enough oil due to thickening oil. this causes compression issues due to smoothing of the hone in the cylinders. I know that there are studies that say oil doesn't break down, but those people have definitely never pulled apart an engine that has gone way past an oil change.

 

Hmmm, never heard of the "quarter tank" rule. Every fuel tank I've looked in that had a submerged high-pressure fuel pump had enough spare capacity when the gauge was on "E" to keep the pump submerged and cooled. As far as sediment is concerned, I recently looked at a plastic fuel tank from a wrecked minivan that had over 300,000 miles on it (and the original pump and filter); there was virtually zero sediment in the tank. Contrast that with the layer(s) of sediment I'd find in older cars with only 100,000 miles on them from the 1980s and earlier (especially those with metal tanks); the difference is astounding.

On the subject of oil; while the oil itself may never break down, the additives that are in motor oil are not so robust (I think we're saying the same thing here). That said, not all oils and their additive packages are created equal, as such, going "way past an oil change" is a relative term. Is 7,500 miles too far to push el-cheapo oil in any given car? Highly likely. Is 12,500 miles too far to push say Mobil 1 in that same car? Probably not. Either way, oil that is beyond its prime will not, in-and-of-itself, cause poor fuel economy, err, unless it is pushed so far that engine damage results.

 

wouldnt a new/clean air filter cut down on emmissions? i mean a completely shut off air filter(in DUST BOWL OKLAHOMA that can happen ) would make the car sputter and probably die.replace the air filter with a piece of cardboard and see what happens.the AIR box on my milly S has a few vacumm hoses coming off of it so wouldnt a restricted/dirty fliter affect vacume to the maze of hoses and solenoids that rely on vacum at that box? i say just change the filter,its probably the easiest job to do to a car.ive spent more time reading about this taday than it takes to change about 15 air filters.it does make sence that the computer will take over and send the correct fuel but only to a point.when your foots to the floor and you can only go 45mph on the highway,sure youll get good gas mileage i guess

 

Please understand, I've never advocated that folks run around with really dirty air filters, just that the old wive's tale of "change the filter every 10,000 miles and you'll get better gas mileage" is totally false in this day and age.