Mileage Drop

[JHD]

I drive a 2000 Avalon that has historically has demonstrated 28+ mpg on the highway. Recently the mileage has cratered to 22 mpg at best. I have the injections system cleaned, plugs checked, etc. with no improvement. I am beginning to wonder about the transmission shift points since the engine seems to go to a higher rpm before shifting. Any thoughts?

[avalon1996]

I drive a 96 avalon xls. there is a sudden drop in town mileage, i'm getting 28-30 miles on highway and 15 miles in city. there is an oil leaking underneath when i park the car.

any ideas...??

[cexsiman]

rear valve cover gasket?

its a hard place to see if the car isnt up in the air, an one many people forget about.

just did mine and solved my leak so far

[CupCate18]

I just had this fixed too. Still got some leak somewhere, only time and money can tell.

[aigochamaloh]

Originally Posted by avalon1996

I drive a 96 avalon xls. there is a sudden drop in town mileage, i'm getting 28-30 miles on highway and 15 miles in city. there is an oil leaking underneath when i park the car.

any ideas...??

Total thread jack, ...

Like mentioned previously, probably the rear valve cover gasket.

As for the OP, are you getting any engine codes or check engine light? It is a possibility that an O2 sensor took a dump, but the OBD2 computers are smart enough to know when that is happening. Still doesn't hurt to check the O2 sensors out.

[JHD]

O2 sensor is a good suggestion. I will check it out. I am not getting any CEL but I have not checked to see if I am getting any codes. Thanks

[swiftjustice]

Do they sell reformulated gas where you live in the winter? Every year here in the Sacramento valley they sell reformulated gas (more ethanol in the mix) to help with air quality during the winter months - my mileage always goes down 10% until they stop selling it again during late spring.

[aigochamaloh]

Originally Posted by swiftjustice

Do they sell reformulated gas where you live in the winter? Every year here in the Sacramento valley they sell reformulated gas (more ethanol in the mix) to help with air quality during the winter months - my mileage always goes down 10% until they stop selling it again during late spring.

That is true, they do add MTBE during some months to combat pollutants, but does that explain the OP's 6 or more mpg drop? That's kind of harsh. Also a good thing to look at though.

[CassisPearl]

Originally Posted by swiftjustice

Do they sell reformulated gas where you live in the winter? Every year here in the Sacramento valley they sell reformulated gas (more ethanol in the mix) to help with air quality during the winter months - my mileage always goes down 10% until they stop selling it again during late spring.

Bingo!

I was just about to post about reformulated gas, but you beat me to it, SwiftJustice. Good call.

Not surprisingly, beyond a drop in mileage, there'll be a drop in performance too this time of year.

[csaxon]

The 02 sensors begin losing efficiency around 90,000 miles. I'll assume you checked the air filter.
It's normal for your trans to have higher shift points when it's cold to allow for faster engine warm up. Once, the trans reaches operating temp the normal time from park/neutral to drive is 1.2 secs or less and from P/Neutral to reverse is 1.5 secs or less.