Robbed gas mileage!

[FLSilverP5]

Ok I changed the spark plugs to Bosch Platinum. Like an extra 5 miles per tank. Pretty bad for dropping 30 bucks on the plugs. I have upgraded from horrible gas (cumberland farms) to chevron. Next tank will be mobil. Let you guys know how its going. But no matter how hard i try to drive good, my foot and the car seem to trick me in unison into driving not so good.

 

[Devman]

There's GOT to be something wrong wtih your engine... maybe timing? Off just a fraction and it's screwing up detonation or something?

I make 35-36 highway with the A/C on intermittently. Current setup is Forza headers, Liveonspeed CAI, UR crank pulley and a Magnaflow catback. That shouldn't get me 10 mpg better, though. The only thing I can think of is timing.

Devman

 

[GNO]

There's GOT to be something wrong wtih your engine... maybe timing? Off just a fraction and it's screwing up detonation or something?

I make 35-36 highway with the A/C on intermittently. Current setup is Forza headers, Liveonspeed CAI, UR crank pulley and a Magnaflow catback. That shouldn't get me 10 mpg better, though. The only thing I can think of is timing.

Devman

From reading the board, I've noticed that these cars have a huge range in fuel economy. Some of us have poor fuel economy, others are at a decent level and then there are those with exceptional fuel economy (such as yourself).

There are a lot of factors, but I think the A/F mixture being leaned out a bit would help considerably. One thing I've benefitted from, as mentioned earlier, was fixing the rear brakes. Then of course, driving habits take their toll as well.

On the subject of leaning out the mixture, just out of curiosity, how long does it take for your exhaust tip to blacken? I've had my Mazdaspeed on for 3 weeks now and the lower part gets black within a week. On my other car, I only had to polish the tips every other month.

 

[Devman]

I don't have my car right now as I'm at college, but my recollection was that it took about 3 weeks to get good and sooty. It's possible you're running far too rich and that's hurting your economy. I'm concerned on the other end of being too lean and burning the seals.

Devman

 

[GNO]

I'm not sure if the Mobil station had much to do with it, but with other cars in the past I've seen 10% increases in fuel economy when filling up with Mobil while travelling through Illinois. I've also seen slight increases when using Chevron, again while out of state. Here in Iowa, there aren't many of the "big" names to choose from. This Mobil station opened up a few months ago in a tiny town about 15 miles north of where I live. The regular there was 89 where most stations sell 87. Unfortunately, they have ethanol with Super and Premium, whereas most all other gas stations in my area have an ethanol blend for Super only. I've filled up with Premium before at BP (92) and 66 (91) and noticed no increase in fuel economy. This last tank, I filled up at the 66. If the fuel economy goes back down, I'll be heading north regularly to fill up at Mobil.

Just wanted to follow-up on this thread although I just posted on another. The tank from 66 only got us 26mpg and we filled up at Exxon/Mobil (that's what was on my cc bill) again. My wife's been driving a lot more aggressively than normal on this tank. Currently it's at 330 miles with a 1/4 tank left. It will easily exceed 30mpg despite my wife's driving habits.

 

[mcstark]

I bought my car last September, and I've been keeping my gas mileage on a spreadsheet since I bought the car and my current average is 24-25 MPG. But the range is from 20MPG (during the winter) to 29MPG (in the summer). My car was real sluggish during the winter - especially when the air temp hits < 10 degrees. But I've switched to Mobil 1 5w30 and hope to see some improvement this winter.

Note that this summer I've averaged 27-29MPG just about every week. I do about 20 miles/day of city driving, and am on the highway very little.

I shift at 3000 rpm in first through fourth, and into fifth at 2500 rpm. I can keep up with traffic, and rarely rev past 5000 rpm when I'm passing. Another factor is I usually only press the gas about halfway down when accelerating.

There's such a wide range of mileage out there, because there are a lot of factors affecting your gas mileage. To name a few: how hard you press the accelerator, how high you rev the engine, how much air pressure is in your tires, what type of traffic you drive in, the ambient air temperature, road conditions, etc. Some of these you can't control (road conditions, air temp, etc), while you can control how you drive. I don't always shift as I mentioned above, I like to rev my engine and some days I will really wind it out - but that's not every day. In a typical week, maybe 1 1/2 days are driving hard, the other I'm pretty calm.

I plan on having this car in 8 years, so I can't abuse it too much now.

Just my .02.

 

[DeanSweet]

actually, try running like 65mph during one of your highway sectors. I don't know what rpm's you guys are running on manuals at 80mph but in my auto its well above 3k. If I keep my car below 3k for rides to and from work I get into the 30's mpg. My normal driving keeps me around 26-28mpg.

 

[mcstark]

actually, try running like 65mph during one of your highway sectors. I don't know what rpm's you guys are running on manuals at 80mph but in my auto its well above 3k. If I keep my car below 3k for rides to and from work I get into the 30's mpg. My normal driving keeps me around 26-28mpg.

DS - If I remember right 75 is about 3500 rpm in a manual, so 80 would be closer to 4000 rpm. I may be wrong as it's been a while since I've been on the highway.

 

[iLisa]

I just got 380 miles on my last tank of gas..

 

[FLSilverP5]

it is about 3500 RPM at 75. But just to update you guys, i used gumout fuel injector cleaner and got 375 miles on the tank (350 wen lite turned on). But i also used chevron gas. I am not testing if it is the gas or the fuel injector cleaner. WIll keep you updated

 

[+ friction]

In one stretch last week driving to Illinois, I got 35MPG w/AC on (well, 34.98something). When I switched to Synthetic blend, my mileage seemed to go up a bit.

Manual + K&N is all I have going for me otherwise.

 

[Devman]

Interesting fact: Cars are usually designed for optimum aerodynamics at approximately 65-75 mph. I drive at the top end of that on the highway (75mph), so perhaps that is a factor? 80 would create significant drag?

Devman

 

[suburbs98]

I have a strange question for you guys. Just moved from Utah to Michigan. In Utah I averaged about 400 miles per tank. As soon as I moved here, it dropped to about 300-320. Why is that? The only thing I could think of was elevation or humidity changes but that makes no sense. Maybe it is time for new spark plugs and a K&N air filter. What kind of sparks do you guys recommend?

 

[dosle]

I have a strange question for you guys. Just moved from Utah to Michigan. In Utah I averaged about 400 miles per tank. As soon as I moved here, it dropped to about 300-320. Why is that? The only thing I could think of was elevation or humidity changes but that makes no sense. Maybe it is time for new spark plugs and a K&N air filter. What kind of sparks do you guys recommend?

i know in wisconsin here we have the shittiest gas mix for enviromental reasons. could be a factor.

 

[FLSilverP5]

That drag question is a good point. You people who are getting amazing gas mileage, do you have roof racks?

 

[+ friction]

That drag question is a good point. You people who are getting amazing gas mileage, do you have roof racks?

yeah, I have a roof rack.

 

[dosle]

That drag question is a good point. You people who are getting amazing gas mileage, do you have roof racks?

no roof raks, k&n typhoon intake, obx header.

that helps

 

[mcstark]

I have a rack, but as previously stated, I do mostly city driving so aerodynamics probably doesn't come into play. I'm going away tomorrow on a road trip, so I took off my rack -- they decrease your fuel economy by about 10%. But the reason I took it off is because it makes a LOT of noise. I'll be able to cruise at 70-75 with the sunroof open and not get any buffeting.

Like I said, they're a ton of factors that effect your fuel economy. The grade of gas -- I always use Mobil 89 octane -- the altitude/air density, etc. With an altitude change, you may just want to reset your ECU as it adjusts the air/fuel mixture to the air density (altitude & temperature). Otherwise it will probably take a few weeks for it to adjust. To be honest, your car should feel a little faster now, because there's more oxygen in the air at a lower altitude and our engines seem to run rich anyway.

Just my .02

 

[bootsie]

Very interesting topic. I am only getting around 330 miles on a tank in MN. I am running on 17" wheels, but that should make that big of adiffrence!! Time to change plugs and do a tune up!!

 

[suburbs98]

Ok, I'm going to change the spark plugs, get a k&n cone filter and reset the ecu. My only question is how to reset the ecu. Is it done by simply removing the battery terminals for a period of time? Anyway, what are the best spark plugs out there.