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Discussion Starter · #1 ·
Hi guys, I got a 2002 rav4 4 sp. It's got 166k miles and this past weekend I got an oil change, coolant change, and fuel system service. I began noticing that my mpg was getting worse starting about two months ago. I used to be able to get about 330-340 miles to the tank on the pure highway and about 300-320 in the city. I occasionally drive from Santa Barbara to the bay area to go home and that trip would drain the tank but wouldn't leave me empty. When I went home last month, I wasn't able to make it one fillup in either way. After the fuel system service this weekend, my mpg saw a major increase. But that was only for one day. I got almost 400 to the tank and that was driving from the bay back to Santa barbara. Now these past few days, my mpg has been really crappy. I used to get at least 160 miles before hitting half tank, now I barely make it to 130. Any ideas as to why??
TLTR
Been noticing that my mpg has been dropping(320 tank to 300). Did fluid changes and fuel system service and noticed mpg were up(almost 400 tank). The next day after the services, mpg is worse than before(130 half tank=260 full tank).
 

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Discussion Starter · #28 ·
Keep in mind I'm sharing advice or recommendations from a 2AZ-FE perspective, but our RAV4.2s still have more in common than otherwise.

1) My experience with unexplained worsening gas mileage has been attributed to slowly failing O2 sensors, on x3 different Toyota vehicles: x2 RAV4.2, x1 Tundra.
2) My alignment is readjusted every 3,000 miles . . . because it needs to be. That's how quickly they can come out of adjustment.
3) Tire pressures change with season. Pending no action by the owner/operator, they go softer in the winter, firmer in the summer.
4) On the subject of tire pressures, if your RAV doesn't have TPMS, be sure they aren't slowly going flat due to damage.

This is puzzling :unsure: A fuel system cleaner shouldn't be providing greater performance "during" the treatment. The combined chemical effects of PIB, PEA or PIBA should have the opposite effect on fuel burn: it's reducing the fuel's octane and introducing larger amounts of contaminated fuel. The benefit of a fuel system cleaner are realized "after" the treatment. This sounds like you got snake oil instead. What product was used for this?

Andeleon, I would recommend you replace the O2 sensors in your case.


Sounds like you've done a good job covering the bases. I think your RAV4.2 is either running pig rich, or the engine is pulling a heavy load. I do 350 miles in the city and 450 miles highway with my 2AZ-FE on OME suspension and taller tires.
Things to look for if it's running rich: 1) How does the air filter look? 2) Is an injector stuck open? 3) Is the ECM commanding the injectors to run rich? (ECM error).
Things to be aware of if the engine is continually under load: 1) What size tires are you using? 2) What pressures do you run? 3) What aftermarket accessories have you installed?

I'm not the most knowledgable with the 1ZE-FE, so here's some documents you may find useful:
I might also start a thread discussing fuel additives, the chemical compositions, how often to use, where not to use, and the fact that non of them work as well as the manufacturers want you to believe.
whoa, you know your stuff man. that's sick. uhh, I will try to understand what you said 馃槀馃槀馃槀. so I got some tiger paws on my car 馃槗 I think 235/70. I pumped them up to about 32 psi on my trip home which was like two weeks ago. no aftermarket stuff on my car unless you count the radio transmitter for Bluetooth music lol. but thanks ill try to check for signs of running rich. It's been about a week since I first posted and my mpg is still crappy. slightly better than that initial run but still getting about 270 to the tank. I thought maybe it was just some shitty gas(is that a possibility at all?) cuz I filled up at a new place that was just built, and for the next fill-up, I went to my go-to which is fuel depot(89 octane). Idk how good of a gas they supply but I think it is good and cheap. The 400-mile tank run was with fuel depot.
 

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Discussion Starter · #29 ·
I haven't read all of this post so perhaps this is covered already.
Tire pressures. Especially the high profile tires, a small difference in pressure can really affect the mpg.
Could it be that part of the service included unintentional over inflation of your tires, giving you better gas milage?
they didn't inflate my tire but I did before I went home. pumped them up to 32 psi before I left and made it home on empty with 330 miles. On the way back checked my pressures again and they were still 32 psi but on the way back I estimate I got about 400 miles since I was down to the final line on the fuel gauge which usually lasts me about 70-80mpg
 

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Discussion Starter · #32 ·
Not really.

I suggested a member had a serpentine belt problem . . . turned out to be worn main bearings.
I recommended a member not use a manual transmission ECM and he did anyway . . . worked fine enough evidently.
My batting average is not great :LOL:

Members in the 4.2 section are just trying to help, we figure things out together. My input isn't any better than the next member's. Worse even in some cases . . .
nah bruh, you don't give yourself enough credit. yea it is a group effort but you know a lot more than what most people know and you've been helpful. So what happened was that I went to get an oil change at an oil change shop. I also knew that my coolant hasn't been changed since I got the car which was like 3 years ago so I wanted to do it as well. They also recommended I do a fuel system service cuz there was probably a lot of carbon build-up or something. While they were doing the fuel service they were revving my car and stuff and soot were coming out the exhaust. They also said that the service would fix rough idling. I don't think my car has had an issue with a rough idle and after the service, it was the same. They also said that the service would increase my mpg which I was hype about because I had been noticing a drop in my mpg as I said before and thought it would fix the problem.
now that i think about it, my car low key does sound a lil different but I usually have my music blasting so I don't pay much attention. I should make sure next time I drive. This post prob didn't add anything to help troubleshoot my problem but dude you're smart and don't be so hard on yourself 馃憤馃憤
 
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