Will adding a drop in K&N air filter increase or reduce gas milage. Also would gutting the cat provide any significant gains.

 

 

No to both questions

 

gas mileage lowering and rx8 shouldnt go 2gether!

 

any increase in power (to a certain point) will increase gas milage as long as you drive slow.

the problem is u won't.... you'll use the power and get worse gas milage.

 

we all use the power. haha

 

Before I put in my cold air intake, I had a K&N filter. I definitely noticed better gas mileage.

 

here this might help.

i drive 170 miles round trip to work everyday @ 75 mph on cruise control.

 

What kind of mileage are you getting now on what octane gas? Air con off/on? Windows open?

 

air off. windows closed, sunroof either tilted or open.

right now im looking at between 1/4-1/3 tank per 90 miles. i still need to calculate my milage.
i alternate between 87 and 89 octance.

 

Where do you get this crap?

Power = fuel in an absolute minimum quantity. It doesn't matter how you make the power or how you use it.

 

Maybe It's just me, but you should switch to a higher quality gas, 91 or 93(if available in your area) dont know if that will help, but in my other cars that used premium if I ever put a lower grade than my MPG sucked and plus I wouldnt trust that low grade crap.

 

At the most it sounds like youre getting around 23-23.5MPG. I think thats pretty good for 75MPH.

I really don't think there is a lot that us owners can do to really increase the mileage exponentially. You could use a really high mileage low rolling resistant tire, but of course your handling would go downhill.

I think you're pretty much driving in a way that maximizes the mileage at the speed your going. Maybe increasing octane will help. I have never run a full tank of 87 in my car only 91.

I am thinking of getting the K&N air filter only b/c they make good air filters that are washable/reusable. I am not expecting any HP or MPG gains.

I did get the new flash and it seems to have dropped my mileage about 1.5-2MPG.

 

I think what Razz is saying is that some mods to increase power can have a positive effect on fuel consumption - (except F/I perhaps) . I know this is true for my piggyback - I am definately getting better MPG since fitting it - even though I tend to floor the throttle more than I used to .
It is leaning out the mixtures on anything above 30% throttle - I am mostly driving around town so I tend to be in this range a lot.
Getting an extra 2 mpg approx.

Also - anything that is done to minimise rotational losses has to help with MPG - IE underdrive pulley ,L/W flywheel , lightweight wheels - perhaps not majorly but anything that reduces the power required to accelerate the car has to increase MPG. Of course if you always floor it - this all goes out the window.

 

I don't see how K&N filters can really help you get better mileage, and with regards to them being washable... a decent paper air filter will clean your air better than a K&N and last at least 10000 miles with a similar air flow, so by the time you've run thru 5 cleaner paper filters you'll have then made up for the cost of the K&N... and you still need to buy oil to re-do it. Oh and if you over-oil it, it will normally cover sensors with it and mess up your readings off of them. I think they're absolutely not worth it from both a wear and care standpoint, and they don't really make economic sense either.

Best way to increase gas mileage is to drive slower, all the other gimmicks out there today are all trash. Optimum gas mileage on cars is usually at 55mph, the 8 will get 27 mpg at that speed.

 

Ofcourse I totally disagree with you on the "aftermarket filter" thing, but I would like to point out this:

Are you 106 years old ? Driving around doing 55mph will lead us to an early grave from boredom......

 

Unfortunately, the only way to get much better than the 23-25 MPG you seem to be getting is to drive it like a granny, or stick a Civic engine in it.

The 23-25 sounds pretty nice. I can't get that too often on the twisty canyon roads I drive.

 

I wouldnt even drive 55 in a Prius. I'd be a hazard in the slow lane on the freeway.

 

Your car seems to get pretty good mileage like mine does. A week or two ago I drove up to Seattle and back. I set my cruise control at 72-73 about half the highway time (70 mph speed limit) and right around 65 the other half. The 72-73 range was right around 3600-3700 RPMs in 6th gear. I ended up getting 27 mpg just barely (27.06).

Try changing your octane. I know my car is pretty sensitive. Changing brands can make my mileage go down. I always use premium gas from Chevron. I have done Shell twice. Both times my mileage dropped from my 23 average down to low 21s and the car didn't run as smoothly.

 

I guess you haven't priced genuine factory Mazda engine air filters for the RX-8 then, have you? They run around $33 discounted from the online Mazda dealers.

You can get a new reuseable K&N drop in air filter for the 8 for about $40 discounted.

Running through 5 genuine air filters at $33 ($165) bucks each is way more than the one-time K&N at $40.

 

who says you want genuine filters, I'm talking like napa filters.

www.bobistheoilguy.com has a very nice article on different air filters, I suggest everyone that is interested read it, it's not super-scientific but it does point out some interesting stuff.

and yeah I said that driving at 55 is the best way to save gas... but no one does it, including me!

 

after i put in the revi (which has a k&n, though obviously different than the drop in) i have gotten almost 2 mi/gal better. my driving style has not changed and i track my mileage meticulously.

 

Best way to get good MPG? Get busted doing 100 in a 65, get 5 pts on the license, then get hit for doing 71 in a 55 while passing someone and get another pt, take a 2 hour course to keep from getting your license suspended and have to drive your brand new 8 at the posted speed for the next two years. I'm expecting some serious gas savings for quite some time if I don't put a bullet in my head 1st. BTW in MD that leaves only 2 pts left before they take your license. May as well buy a 90hp beater for the next 2 years.

 

Drive a Fit.

 

Actually, their filters are not all that good, OK, but nothing special. The way they get the high-flow numbers they publicize is by using a fresh filter, and a fresh K&N filter will pass gravel, medium-sized insects, and bird ****.

By the time their filtering specifications get to the same level as a new paper filter their flow numbers have dropped back to that level, too.

If, on the other hand, you just like washing an air filter, well, K&N's the way to go. Keep in mind, though, that every time you wash and oil it you have to go through the process of getting it dirty before it becomes decent protection for your engine.

Pilgrim