K&N Air Filters/Synthetic oil.
 

Ok. I saw in the "sticky where K&N air filters were busted for aiding fuel economy.....I think I also saw where the syn oil was busted.....I got an additional 40 MPT out of my sunfire after changing to syn oil and installing a k&N...Help I am confiused.

I think both would contribute to a very small increase if any. The only problem I have with K & N air filters, is that their filtration is worse than a regular paper air filter. So more air + less filtration = shorter engine life. As far as synthetics go, the oil is more uniform and tends to break down slower than convetional. So better oil + good filtration (oil and air) = longer engine life. Also if your running a synthetic you should see what the ACEA number is on it, so you can do extended oil drains.

Borrowed from the ACEA European Oil Sequences 2007

A/B : gasoline and diesel engine oils
A1/B1 Oil intended for use in gasoline and car + light van diesel engines specifically designed to be capable of using low friction low viscosity oils with a High temperature / High shear rate viscosity of 2.6 to 3.5 mPa.s. These oils may be unsuitable for use in some engines. Consult owner manual or handbook if in doubt.
A3/B3 Stable, stay-in-grade oil intended for use in high performance gasoline and car + light van diesel engines and/or for extended drain intervals where specified by the engine manufacturer, and/or for year-round use of low viscosity oils, and/or for severe operating conditions as defined by the engine manufacturer.
A3/B4 Stable, stay-in-grade oil intended for use in high performance gasoline and direct injection diesel engines, but also suitable for applications described under A3/B3.
A5/B5 Stable, stay-in-grade oil intended for use at extended drain intervals in high performance gasoline and car + light van diesel engines designed to be capable of using low friction low viscosity oils with a High temperature / High shear rate viscosity of 2.9 to 3.5 mPa.s. These oils may be unsuitable for use in some engines. Consult owner manual or handbook if in doubt.

i am sorry i dont follow you there.. its not like he is using any kind of forced induction...

The K & N Air filters allow more air to enter and filters less than a paper air filter. So if air flow goes up so does air contaminents. In this situation you would need better filtration to compensate for more air. Since the K & N air filter does not offer this than your engine will suffer with particles. Even though it's at the micron level, it's still not good. Hope I cleared it up.

I actually took my own advice this summer and pulled out the K&N. Sold it to someone with the same kind of motor who cares more about WOT airflow than I do.

I stuck the stock paper filter back in the car.

It proves nothing to say this, but the OEM filter was in use for the majority of the 104 mpg driving of the last fill-up.

Whoever wrote that about synthetic oil was wrong, that's all. Reduce friction, improve efficiency. That's well documented elsewhere. I use the thinnest synthetic I can get away with, in the engines, transmissions, power steering, rear end, etc, and that does work.

As for K & N air filter, that certainly isn't going to help mpg unless you happen to be replacing a badly plugged paper filter with it.

If synth was proven to improve efficiency over equivalent weight dino oil, you'd better believe the oilco's would be touting it in their marketing. They're not.

Its ability to improve efficiency applies to a very narrow range of temperature-dependent circumstances (ie cold weather starts), and even there the improvement is tiny.

yesterday I had my car parked in an area that was dusty, the entire inside and outside of the car is covered in this fine dust, it's fine enough that I'm sure it would have passed right thru a K&N filter, this is based off what I've seen while rebuilding carburators on motorcycles with K&N filters, because of this I have a foam air filter with hi-tac filter oil, my intake is clean enough to eat off.

I'd go by mpg for the tank otherwise how can you fill the same each time to compare accurately using miles per tank? In other words error could account for some of the difference you are seeing depending on how you fill up.