Sudden loss of MPG on my 2005 Scion xB

Hey all! I bought my 2005 Scion xB (automatic transmission about 42K on odometer) in NH shortly before moving to Los Angeles last year. My wife and I drove the xB over 3500 miles from New England to LA in August last year and even fully-loaded up, we averaged an impressive 34 MPG going about 70mph on the highway the whole way (sometimes AC on, sometimes windows, sunroof open).

After arriving in LA, we have noticed a significant drop in MPG! Granted, it’s a lot more stop-and-go driving in the city, but even on road trips (highway driving), we’ve dropped to 29-30 MPG! Further, the car seems to have lost a bit of acceleration as well (though tough to prove on a car that never really had any to begin with).

The car has about 53K miles now. We have regular oil changes, air filter looks clean enough, tires inflated properly. Maybe it’s the spark plugs? Someone thought it was the 10% mixture of ethanol in the gas out here.

Any thoughts?

-Dave, (now) from LA

Have the spark plugs ever been changed? The original equipment plugs should have been replaced at 30k miles. The ethanol can also hurt your mileage a tiny bit as you’ve heard.

Imperial gallons are larger than American gallons. So the 34 MPG you saw over there is closer to 27 MPG U.S. or so. Your car is rated for 27-32 MPG. The 29-30 MPG. You care getting seems perfectly normal.

I don’t think the spark plugs have been changed.
This may account for the sudden loss in MPG and performance.
I’ll look into it.


Your kidding, right? New Hampshire uses US Gallons just like the rest of the 50 states!

dtlewry, don’t listen to that crap. The problem is most likely the difference in fuel formulation. EPA mandates different gasoline blends for different regions based on many regional factors. LA blends require a large amount of oxygenators, which reduce smog producing compounds, but also reduce mileage and performance. Unfortunately, there isn’t anything you can do about it, but live with it.

FD–The OP moved from NEW England, not from England, so the size of the gallon is not the issue here.

As Xebadiah noted, the old spark plugs and ethanol are the likely culprits, along with good old LA traffic patterns.

While you are at it, check the Toyota maintenance schedule to see what other maintenance procedures may have been skipped, in addition to the plugs.

And, even if the maintenance schedule doesn’t list it, be sure to have your transmission fluid changed. That won’t save you any gas, but it will likely save you from having to get the transmission overhauled at 90k.

BustedKnuckles, thanks for the info.
I didn’t even think to compensate for (let alone was even aware of) oxygenators and their smog-reducing, but MPG lowering, effects.

I guess the next step would be to find out what other LA-based Scion xB owners are getting for MPG…maybe my numbers aren’t that bad in comparison.

Thanks for the post!

Sorry, I didn’t didn’t see the “New” in New England in your original post. My mistake. I misread it and thought you went across the pond and drove a Scion.

Good point.
The maintenance schedule fails to mention many of the “typical” maintenance services that are needed (ie transmission fluid and radiator fluid flushes) regardless of the vehicle’s make or model.

Other things could be happening too. You might have taken on salt water after the drive across the ocean… The Summer gasoline blend may be better but I don’t really know if your area is cold enough for a Winter blend to be used. It can be cool in Westwood but I don’t know how cool it has to be.

I got good mileage in my Saturn Vue when I took three trips to San Diego from Santa Barbara in 05-06 from November to February.

An 83 Corolla would give you 41 MPG on a Ca. highway if it was equipped with a cassette tape player as the only optional equipment. The computer remembers what kind of driving is done and tries to adjust for it. You also have some awful hills to climb too. 405 is no fun to drive on.

Which route you drive can make all the difference. Oxnard to Ventura is easier than Oxnard to Anaheim. Don’t forget to try to find Coco’s in Calabasas. Don’t miss the driveway or you will end up on the highway. See if that Ford Falcon is still parked there.