2000 Avalon poor gas mileage

[eleven]

I have a 2000 Avalon, 3.0 V6 engine (they all were, I believe)
This was my folks car which I have inherited. It has a mere 43K miles on it. Surprisingly, the automatic transmission failed (torque converter) about 3K miles ago, which set an error code which would not let the car pass CA smog inspection. So that had to be fixed or the car would have been a near-junker even though it still drove fine with that fault. (A little balky moving into highest gear, though, when cold) I suspect that my folks failure to change tranny fluid in ten years was the likely cause. Anyway, that work was done and the car drives fine. With 43K miles it should be OK as an entirely comfortable (and paid-for!) car for another decade.

My impression is that it gets really atrocious gas mileage. Maybe 13 mpg city, 18 hwy. I know it is a heavyish car, but it seems to me reading posts on this forum that its mileage should be at least 40% higher. Around town (in terms of being able to see the fuel gauge move on a silly 8 mile errand trip) it's like driving a giant Detroit car from the 70's...it's almost like I can see the gas gauge move. I DO know that the fuel gauge is quite nonlinear...when full, 50 miles of driving hardly moves it. When low, 10 miles is definitely noticeable.

I don't think there is anything grossly wrong with the car in terms of fuel mixture or things like that, or else it could not have passed smog.

I am soliciting anyone's "top ten" suggestions for improving gas mileage on an otherwise perfectly functioning Avalon.

Many thanks in advance for all who may opine!

[buchaja]

Off the top of my head:

Change the fuel and air filters and maybe have the fuel injectors cleaned. Somewhere on here I read about an air/fuel detector (MAF, anyone?) that needs periodic cleaning. Your tires air pressure should be checked.

No top ten, but that's all I got other than to tell you I get ~17mpg. in all city driving.

Oh yeah, the throttle body could be dirt and need cleaning too.

Good luck.

[OHC]

Some other things that might help: Low rolling resistance tires, have the alignment checked, and if you're heavy on that pedal, try lightening up a little!

[TrailDust]

In the nine year's I've owned my Avalon I've consistently gotten 21/22 city and 29 (at 70 MPH) highway/31 (at 65 MPH). Other than the obvious things like changing the air filter, buying low roll resistance tires and inflating them at 32 to 35 PSI, you've got to pay attention to coasting as much as possible in city driving and keeping your speeds reasonable on the highway. I've got to say that of all the cars I've owned in my life my Avalon has the lowest roll resistance I've every experienced, and add to that the vehicle's weight and aerodynamics, and you've got a car that wants to keep on rolling and rolling. Driving (particularly in the city) is all about energy management, just like sailing a boat or flying an aircraft. Manage the energy properly, and your mileage will certainly improve.

[buchaja]

I think my mileage improves when we get into the Summer blend fuels, but not much. Ten percent perhaps.

Unfortunately, I am at the mercy of the local traffic flow here. It's all stop and go. I wore through the original tires before 30k miles; the struts too.

That's an interesting observation about your rolling resistance, TrailDust. I think my F150 coasts better than my Avalon. But, I only get 12.86 mpg (city) in that beast!

[eleven]

Thanks for all the suggestions so far! I truly appreciate it. Maybe the tire inflation could use a few more lbs, as I primarily drive around town on short hops and thus I doubt the tires get freeway hot.

Question to those quoting mileage figs: Are you using the internal dash-computer or do you go "manual", eg; fill to tippy-top, reset the odometer, then drive until you're down to fumes? The reason I ask is that the instantaneous mileage dash-computer gives some numbers of which I am skeptical. If I stomp on the gas (and this isn't my habit in my demure suburban area but I ain't a retired librarian, either!) I can get that number down to 5-6-7 mpg. Coasting down a smooth 35-40 mph street once up to speed I can get it to 70 mpg. The price of gas isn't anything to joke about these days so I pretty much take it easy. But sixty four bucks (ouch!) tossed into a practically bone-dry tank is 15.23 gals @ 4.20/gal and about 210 miles later I'm dry again. That's under 14 mpg.

So: dash computer or real-world consumption test?

[buchaja]

I'm going by my computer, but I have hand calculated it several times and found it to be fairly accurate.

I know what you mean about the instant read-out. It's like a game to me the few times I switch over to that mode. I've actually seen 99 on some long down hill coasts.

My neighbor apparently just got rid of her two year old Mustang for a Prius. I guess she's expecting $5/gal. soon. It's funny seeing her in such a radically different vehicle but I get her reasoning.

[TrailDust]

Originally Posted by eleven

So: dash computer or real-world consumption test?

When I compute mileage I'm always going from fuel lip to fuel lip, as in I fill up my tanks literally to the brim of the fuel spout. And before anyone says it, let me state that I've been doing this in every vehicle I've owned the last 30 years and never had an issue. Anyway, I calculate based on real world observation and not computer.

[eleven]

Thanks guys! I've also gotten suggestions of an injector-system clean/flush and I have little doubt these are the original factory spark plugs in it. I'm sure I can take it somewhere where "maintenance-induced failure" could snake maybe almost a grand out of my pocket....but the fact is that even with only 43K miles on it, it's still a 10+ year old car and certainly hasn't been maintained. Could easily have some gunk in the fuel system.

[justdoug]

I have read a few responses to your inquiry and I think most all of them are good. Given the age, (not the miles) I would suggest doing a basic tune up. That would be new plugs (sorry, the rear 3 are pretty tough), air filter and PCV valve. Also, I have seen O2 sensors that hurt gas mileage without throwing any codes, so that could be a culprit. You may want to have the ECU scanned just to see what codes are in there. You mentioned the car didn't coast all that well. I would make sure your parking brake cables were free and loose when the P brake is disengaged. You could have a caliper sticking and that will defiintely hurt gas mileage, not to mention getting a rotor to glow cherry red. Make sure you aren't carrying a load of bricks in the trunk too. I would be curious as to what condition your transmission fluid is in? There could be an issue in the transmission as well causing excess drag on the drivetrain, but I will hope this is not the case. When you need new tires, I would strongly consider the LRR variety, but I don't think you need to rush out and get them if your present tires are in good condition. They might help you by 1 mpg, but that's paying you back the whole time they are on the car. I doubt its in any of the wheel bearings running too tight or they would be making noises, especially when you go through corners. The last thing I can think of would be some kind of exhaust restriction. Cats don't usually clog until much, much later than this. But your parents may have driven over a parking curb and flattened an exhaust pipe underneath the car. I will wish you the very best of luck in resolving this problem.

[eleven]

"I have read a few responses to your inquiry and I think most all of them are good. Given the age, (not the miles) I would suggest doing a basic tune up.

Probably the ticket.

"That would be new plugs (sorry, the rear 3 are pretty tough), air filter and PCV valve. Also, I have seen O2 sensors that hurt gas mileage without throwing any codes, so that could be a culprit. You may want to have the ECU scanned just to see what codes are in there.

"You mentioned the car didn't coast all that well. I would make sure your parking brake cables were free and loose when the P brake is disengaged.

No, perhaps you misread. The tranny was rebuilt ~~3K mi ago, so I'm reasonably confident that the fluid (and all else) is good. I'll check the P brake (which I almost *never* use unless I'm on a fair hill)

"You could have a caliper sticking and that will defiintely hurt gas mileage, not to mention getting a rotor to glow cherry red.

Wouldn't I maybe smell that after entering a garage & then closing the door? I'll pay some add'l attention to that next time I return from a trip. Good suggestion!

"Make sure you aren't carrying a load of bricks in the trunk too. I would be curious as to what condition your transmission fluid is in? There could be an issue in the transmission as well causing excess drag on the drivetrain, but I will hope this is not the case.

You and me both. As above, I have to consider the 3K-mi-ago rebuilt tranny (and its fluid) "new"

"When you need new tires, I would strongly consider the LRR variety, but I don't think you need to rush out and get them if your present tires are in good condition. They might help you by 1 mpg, but that's paying you back the whole time they are on the car.

Tires are pretty new vanilla Goodyears, nothing special, not showing mis-alignment wear and in good shape. The car is only driven around town, really, but 15-20 qty 10 mile trips, it seems, and the sucker is drained. It's annoying. And costly.

"I doubt its in any of the wheel bearings running too tight or they would be making noises, especially when you go through corners. The last thing I can think of would be some kind of exhaust restriction. Cats don't usually clog until much, much later than this. But your parents may have driven over a parking curb and flattened an exhaust pipe underneath the car.

Maybe a bearing lube would be a good idea though, just on GP.

That's (exhaust sys crimp) an interesting suggestion. The car was in a mid-grade accident, it was front ended by a cel-phone talker gal. I would imagine that the repair shop (very good reputation) would have taken care of such non-obvious things, but one never knows unless one checks.

"I will wish you the very best of luck in resolving this problem.

I really appreciate your suggestions! I should probably bite the bullet and throw a grand at the thing. 43K miles on this car is almost new. And the sooner I bite the bullet, the better (and for longer) the gas savings will be.

Should I do that and find an obvious 5 mpg culprit, I'll report back! Thanks again!

[ChiTDI]

Syn oil and syn ATF will make a difference too, but you might want them to check for a vacuum leak during your tune up. That will drop mileage dramatically.

[TedL]

After checking your brakes, focus on your fuel control. Brakes: Jack up jack wheel position, apply brakes, release brakes, spin by hand. If you don't know "normal" effort, you should learn by wheel 4. Front take more due to axles.

Invest $100-150 and get a scan tool that gives data as well as codes. If you want to be a DIY'r, it's needed and well worth it. Right now, you're working in a way that's like using a PC without a monitor.

Look at the fuel trims.

The 2 AFR sensors have a lot of input that determines the injector pulse width. They're expensive to start part swapping ($250+ for 2 AFR and 1 O2S online), but they can be "off" without being so bad the system says "that value can't be right" and sets a code.

The system also gradually "remembers" how it has adapted to your driving style. It may still be remembering the former owners half mile trips, never warmed up. Disconnect the battery for 10 minutes to reset to baseline. Be prepared for a stall or two as it relearns how to idle.

Spark plugs (just to be sure) and secondary ignition cables (age!) s/b be changed. Use OE wires, and the Toyota spc'd plugs (NGK or Denso).

[CT_highlander]

I don't know if your Avalon has a hidden charcoal filter in the air box, but if it does... I would pull it out.

[pmesfun]

Does the car reach normal operating temperature, 1/2 way mark?