G20 Gas Mileage

[metmdx]

I just found this board so please forgive the probable duplicate question asked elsewhere, but I have a 1994 G20 A/T.. Never get more than 26 hiway @65-70mph and around town avgs somewhere between 17-19. To me this isn't up to snuff. I've been told that replacing O2 sensor will alleviate problem (i.e. better mileage by as much as 3-4 mpg). Is this expensive part? Can I do it myself (I'm fairly mech. inclined). Any info is appreciated.
Thanks,
metmdx

[A380Driver]

26 MPG is about as good as ur gonna get thats pretty much up there with average. You could replace ur o2 and see if it helps but i dont think you will see any gains past 26.

[Cue-Ball]

Consider yourself lucky. I've got a 99 P11 with the 5-speed and i average only 23mpg with mixed city/hwy driving. My best mileage so far has been 27mpg but i've only gotten that high on one tank.

It makes me wonder how the 500+hp Supra in this months SCC managed to get 32mpg during their testing. I guess their 86 mile route must have been about 3/4 downhill.

[JustinP10]

I'll tell you this... they must have not got on it at all... once in boost those higher hp cars just chug gas Turbos do make cars VERY efficient.

I've been lucky enough to see mpg's over 30 w/ highway driving, up to 35ish at times. Normal city I see in the mid-high 20s. City could be higher but i'll get on it everyonce in a while, and i don't granny shift, so i'm probably wasting gas due to that. I know when i was breaking in my clutch, and granny driving, i got INSANE gas mileage (30+in the city)

[kenchan]

yeh, they try to put the largest possible number, so 25-26 would probably the best you can do... with wind, type of road, type of angle on the road, ac on/off, heated seats on/off, etc.

[napakapa]

if i do hwy, i can hit about30mpg, mixed driving normally about 24

[howard_w13]

Originally posted by metmdx
I just found this board so please forgive the probable duplicate question asked elsewhere, but I have a 1994 G20 A/T.. Never get more than 26 hiway @65-70mph and around town avgs somewhere between 17-19. To me this isn't up to snuff. I've been told that replacing O2 sensor will alleviate problem (i.e. better mileage by as much as 3-4 mpg). Is this expensive part? Can I do it myself (I'm fairly mech. inclined). Any info is appreciated.
Thanks,
metmdx

Assuming you haven't done it yet, you might want to get a JWT POP-charger, which is an aftermarket intake. The stock intake really hinders performance and mileage since it's so restrictive. Also, have you done the normal maintenance checks?( Ex:spark plugs, properly inflated tires, spark plug wires, etc?)

[Yahnozha]

I do a lot, and I mean a lot of highway driving, as my odometer now reads 82,220 on my 99.

TIRE PRESSURE!! This probably makes the biggest difference in milage for your vehicle, make sure all four are the same, but play around with it. I ride at 35 psi and that gives me the best milage on stock....with the JWT POP and UR Pulleys I noticed an increase of about 3 mpg, and I normally drive between 75-85 mph. I also put premium gas in but dont know if that really matters, some say it does some say it doesnt....just my two cents tho...

[howard_w13]

Originally posted by Yahnozha
I do a lot, and I mean a lot of highway driving, as my odometer now reads 82,220 on my 99.

TIRE PRESSURE!! This probably makes the biggest difference in milage for your vehicle, make sure all four are the same, but play around with it. I ride at 35 psi and that gives me the best milage on stock....with the JWT POP and UR Pulleys I noticed an increase of about 3 mpg, and I normally drive between 75-85 mph. I also put premium gas in but dont know if that really matters, some say it does some say it doesnt....just my two cents tho...

82k on a '99? Damn, I got a '95 and just got to 105k! As for the premium gas thing, the two major mods that would give you the most bang for your buck are advanced timing and a JWT ECU upgrade.
http://www.automotiveforums.com/vbulletin/showthread.php?s=&threadid=9984&perpage=15&pagenum ber=1

[Cue-Ball]

Originally posted by Yahnozha
I also put premium gas in but dont know if that really matters, some say it does some say it doesnt....just my two cents tho...

That actually gives you LOWER mileage and LESS power. Gas with higher octane burns more slowly, so it drives the piston down with less force. The only reason to run high octane gas is to avoid pinging. The '99 G20 only requires 89 octane and that's what you should use.

[A380Driver]

Unless for us who have the ECU upgrade or those who advance their timing

[JustinP10]

Or, stock ecu with advanced timing 19 degrees timing probably wouldn't go to well with 87 octane gas.

[Cue-Ball]

That's true. If you advance your timing you need higher octane. But, as i said, you need it to prevent pinging (detonation). So many people put high octane gas in their cars for "higher performance" when they don't need it.

[Yahnozha]

I guess I should have mentioned that I do have my timing advanced about 17-18 deg. and premium out here in NM is only 91 octane, I think? My bad for not being all informative....

As for the ECU, Im waiting till I get the header/cam/exhaust combination set up for that, which should be next month on the header and exhaust. Im in the process of moving my business right now and to date Ive spent over $5K and looking at another $4-6K before its all done, so those are going to be my "Im done with moving" present to myself.

Come to think of it I could have had a pimp ass turbo by now...#@#^*&!!!