Where oh where did the miles go?



For the past 4 years, have been getting 15mpg (city driving) with my 2004 Sienna. Took the car in for a major 60K service and am now getting, if lucky, 12.4mpg. Of course, Toyota did some diagnostic computer test and pronounced everything A-OK. My driving patterns have remained the same and am filling up at the same gas stations. My husband thinks I’m a lunatic to worry about it. I thought 15mpg was bad (especially when the EPA estimate is 18-20mpg) but now I long for the good old days. This is making me crazy not to mention lighter in the pocketbook - with my driving, it’s an additional tank (approx. $55) per month. What could this be?!


How are you calculating your mileage? Over how many tanks? Any changes in driving conditions? Also, what was done in the 60k service?

I would suspect that since you’ve only lost 2.4mpg, it’s proabably just minor deviations in traffic, weather, number of cold starts, etc. Keep in mind that serious stop-and-go traffic is worse than the EPA “city driving” rating.

Also, have you gone to www.fueleconomy.gov to check the fuel economy of your van under the revised ratings? Your numbers may be right on the number now.


What did they do at the 60K service? Did you take the vehicle to the dealer, or did an independent mechanic work on it?


I took the van to the dealership for the scheduled 60K service (oil & filter, engine filter, tire rotation, more details at the following URL: http://smg.toyotapartsandservice.com/guides.php?v=18&y=2004&int_id=12&done=1) I’m a stay-at-home mom so my travel is pretty consistent, going to the same practices and lessons week in and week out and I’d been getting the 15mpg consistently ever since I bought the car 4 years ago and then all of a sudden the fuel efficiency drops by 17% which is 55 miles per tank - and that’s a lot of gas. I know that you NEVER get the EPA estimate and that’s just the way it is but I’d like to get my old cruddy gas mileage back! I need a “Dr. House” for my car. My car has symptoms but I haven’t gotten any answers yet. Could the fuel be slowly evaporating somehow, although I figured one would probably be able to smell it.

By the way, I’m calculating the mileage via the odometer. One interesting note, the DTE number which always reset insanely high (eg 398 miles) now resets after a fillup at 278 (I guess it uses the most recent tank mileage as a basis for its estimate.

Thanks for replying.


I took the van to the dealership for the scheduled 60K service (oil & filter, engine filter, tire rotation, more details at the following URL: http://smg.toyotapartsandservice.com/guides.php?v=18&y=2004&int_id=12&done=1). I’m extremely frustrated; the dealership did a computer check and said that everything was okay (based upon a 3mile check).


Check tire pressures. Sometimes a new air filter would give you worse mileage for couple of weeks. Also have them check the brakes and make sure nothing is stuck.


I would like to know my tire pressure. Maybe a tie rod end is wearing out, making the wheels point in wrong directions.


Unless they thought your tires were overinflated and let a fair amount of air out, there’s nothing they did that should negatively affect mileage. (I guess there is a very unlikely possiblilty that they put in the wrong viscosity oil, but I doubt that at a dealer)

So have you only noticed the reduced mileage in the last tank? Perhaps the tank didn’t fill up all the way-- that would certainly explain the lower DTE reading (though I don’t really know how that system works on your van). Alternatively, if it was the tank that was in it when it went in for service, maybe there was something in their checkup that required them to warm it up and/or leave it idling for a while-- that would negatively affect your average mileage for that tank. While I appreciate that your “17%” figure sounds more dramatic than my “2.4mpg” figure, with such low mileage in the first place, even tiny fluctuations are going to make big-seeming percentage changes.

By the odometer, you mean fill it up, reset trip odometer, drive through tank, fill up again and divide trip reading by gallons pumped, right? (Just checking-- you should hear some screwy methods you read on this board!)


Another suggestion I’ve just thought of it why not take the kids on a trip out to the country sometime and see how the thing performs on the highway? Your highway mileage is far less susceptible to environmental changes.


Quote: “I would like to know my tire pressure.”

Ummm…Have you thought about buying a tire pressure gauge? Surely that is better and safer than wondering about your tire pressure.


-Check the mileage manually (full tank it, zero the trip odometer; on your next full tank divide the trip odometer miles by the #gallons you put in) and compare this with your carputer’s mpg calc.
-Set the tire pressure correctly by checking it 2 ways (analog, digital); don’t use the “pen” type gauge.
-Use another gas station.
-You may want to try a “Total Fuel System Cleaner”.
-A/C and excess weight also bring down mpg.
-Change your fuel filter.


For some ideas from the Brothers, click on Actual Car Information. Scroll down about 4 screens to Improve Your Car Mileage (or, similar words). Even though the spark plugs are GOOD, a fresh set can make a lot of difference.