Another mpg thread - Toyota Nation Forum : Toyota Car and Truck Forums

Gonzo64 · 03-02-2010, 03:44 PM

Ok well got my 95 camry auto last year. So far so good been treating me really well. I am not getting that good gas mileage its a 4 cyl. 5sfe. Was getting 24 miles to the gallon. It has 97k on it right now. I got the fuel filter replaced with oem and changed plugs and wires with ngk. Also replaced the air filter. I now get 25 miles per gallon. All my driving its highway. It takes me 10 mins to get on the highway going 50 mph and than one on the highway between 70-75. Car never sees anything above 3.5k rpm. Seafoamed it twice (intake and fuel) and put lucas injector cleaner in it for 5 fill ups. Tires are set to 40 pounds. I coast going down hills also. I dont know how people are getting more mpg. I also put super in the tank for two fill ups (93 octane). Did not changed in mpg. So I know the timing needs to be done and I was thinking about getting new tires in the summer just for hell of it. I had alignment done when I put new shocks on the car. Checked the brakes and everything looks good. So any ideas what could be why I am getting not that great of mpg. My 400+ hp talon gets almost better gas mileage. Please help! Thanks

Nervous · 03-02-2010, 03:51 PM

My 96 1MZ Camry is doing 24.7 mpg on a highway....
You did almost everything possible, seems to me. You can also check oxygen sensors (since they affect fuel mixture) and clean MAF / MAP (don't remember which one is in 5S-FE).
Another wild ideas: your power steering pump / alternator is failing and engine is having hard time cranking them. Do you drive with A/C on all the time at any chance, btw?

a94autoCamry · 03-02-2010, 04:07 PM

^ 24.7mpg on the highway doesn't seem good, maybe because your in a colder area??

I'm getting about 29mpg highway (96 1mzfe camry) but I'm in so-cal...

uibalnme · 03-02-2010, 04:10 PM

96 5sfe auto 156k. 25mpg mixed(city/hwy), 35mpg or better all hwy with cruise control set at 65-70.

hill8570 · 03-02-2010, 04:13 PM

So what's the complete trip profile (including stops)? It's those accelerations from a complete stop that kill yer mileage.

a94autoCamry · 03-02-2010, 04:19 PM

to the OP, gonzo you said your tires are at 40psi?? seems a bit high, try 32psi all around.

uibalnme · 03-02-2010, 04:54 PM

I'm getting my mpg with my tires at 40psi. They max out at 51psi. If I put them at 32psi (factory spec), they look like they're going flat. I also get less mpg at 32psi. I've been running my tires at 40psi since I got them over a year ago. I've never had a problem. No issues with blow-outs, handling, or traction.

Nervous · 03-02-2010, 05:02 PM

Quote:

Originally Posted by a94autoCamry

^ 24.7mpg on the highway doesn't seem good, maybe because your in a colder area??

I'm getting about 29mpg highway (96 1mzfe camry) but I'm in so-cal...

Yeah, it is 24.7 now, in cold Maryland.

Gonzo64 · 03-02-2010, 07:36 PM

Quote:

Originally Posted by Nervous

Another wild ideas: your power steering pump / alternator is failing and engine is having hard time cranking them. Do you drive with A/C on all the time at any chance, btw?

Ac not on and barely using the fan.

Gonzo64 · 03-02-2010, 07:58 PM

Quote:

Originally Posted by hill8570

So what's the complete trip profile (including stops)? It's those accelerations from a complete stop that kill yer mileage.

10 minutes to the highway and about 20 minutes on the highway. About 25 miles one way. There is 2 stops. Than 1 on ramp so throttle is more like 40% throttle. 40 to 70. Like I said doesnt go over 3.5k rpm

hill8570 · 03-02-2010, 11:29 PM

Quote:

Originally Posted by Gonzo64

10 minutes to the highway and about 20 minutes on the highway. About 25 miles one way. There is 2 stops. Than 1 on ramp so throttle is more like 40% throttle. 40 to 70. Like I said doesnt go over 3.5k rpm

That does seem a mite low, then. I've got the same car, and I get ~22-23 mpg. Typical trip is ~12 miles with ~6 complete stops; speeds anywhere from 25 to 60 mph depending on the road. With your amount of cruising, I'd expect more than 25mpg.

***fenixus*** · 03-03-2010, 12:11 AM

i would pay closer atention to oxygen sensors. i found one of mine at 70k miles to be giving foolish voltage outputs to ECU and possibly killing the A/F ratio with something like +22% Long-Term Fuel Trim at idle (closed loop) and when cruising. funny that it gets more optimal when i accelerate only (open fuel loop) ... guess my 5sfe current MPG with 75% driving on highways ... 19-22 per gallon (frosty winter was here) haha!!
i used to see 28 mpg on same/similar routes a year before.

was always running 28-32 psi (usually less) in all tires.

i hope i will finally win this battle by replacing the rear o2 sensor. time will tell. i also did full tune up about 6mo ago and cleaned everything possible i think (except evap and egr). only vacuums leak are yet to be confirmed (or better not).

***fenixus*** · 03-03-2010, 11:46 AM

Quote:

Originally Posted by pgmomni

I have run 40 psi for extended periods with no ill effects besides harsher ride. Yoko Avids were fine at 40. My current tires, 14" Firestone Trendsetters are unbearable at 40 and I lowered them to 34f, 32r.

I have read various info regarding the role of the rear 02 sensor.
While it is well known the front AF(wideband) Sensor is a primary input in
closed loop feedback, the rear 02 senors primary role is only to check
emissions/Cat convector efficiency? Some claim it it plays into to fuel trim slightly
others say its only purpose is to monitor exhaust for post cat 02.

If you unplug it the reading goes to 0 or 1 AND the system stays in closed loop.
I have done test drives of 100's of miles with it on and with it unplugged in my current car that has the chronic P0420 CEL due to a failed front cat and gotten the same 32+ hwy mpg.

Pete

well that the thing. i have seen it failing during test engine race (4k rpm in parking lot) and engine got hiccups and almost stalled once when that rear oxygen sensor dropped output voltage to zero (was around 0.57V before). i could not accelerate with it showing zero and front A/F showing 3.7V or so.
maybe if it failed completely the ECU would ignore it completely and maybe that's different if ECU "thinks" it works OK and start showing crappy readings to ECU, i dunno. so far this sensor is the only thing that has faulty readings.

i have yet to finish testing for vacuum leaks, EGR and EVAP operation and fuel system. though i think fuel pump runs OK, never had fuel cut problems at any RPM range except that torture test for rear oxygen sensor (sustained 4k rpm for 3 minutes).

i got zero CELs too which makes it only more funny.

Gonzo64 · 03-04-2010, 08:02 PM

So replace the front O2 sensor might fix the problem? Or maybe resetting the computer. (Pull battery) Is there way to test the sensor to see if its bad

***fenixus*** · 03-04-2010, 09:36 PM

Quote:

Originally Posted by Gonzo64

So replace the front O2 sensor might fix the problem? Or maybe resetting the computer. (Pull battery) Is there way to test the sensor to see if its bad

which sensor is responsible is hard to tell if none of them really failed . it's easier if ECU shows an error (there are two of them pointing to specific sensors in description in Diagnostics manual), but even with this information there is no guarantee that other sensors works 100% right.

i was able to pin point the rear sensor to be partially failing under maintained heavy load and giving waaaay too low (lean) readings. this one i am about to replace.
surprisingly the front one seems to be working fine (voltage wise).

pulling the battery terminal connector (or easier, pulling EFI 15A fuse from relay box in engine bay) won't fix the fuel trims or oxygen sensors. tried that many times, it all comes back quickly (bad fuel trims in my case).