Help! My FE has dropped
 

I've been averaging 29MPG through the winter on my 98 Corolla - 100% city driving here in Vancouver. As the weather has warmed up, I was expecting my FE to go up even more. But instead, the last two tanks have averaged 26MPG and it looks like the current one will be the same.

I'm doing more coasting than ever. Engine off at lights. Safe drafting whenever possible. I feel my that my hypermiling is better than ever, so a drop heading into the summer is especially troubling.

Before I noticed the drop, my mechanic adjusted the e-brake tension and cleaned the brakes. I don't think the brakes are dragging because the neutral coast seems to be as good as before. Oil has just been changed. Tires always at max 35psi. What am I missing? I think I'll change gas stations to see if they're doing anything funny with the mix.

I'd look at the air filter, plugs or maybe the muffler.

Pump the tires up to 50 psi. I had the same problem.

Air filter looks clean. Plugs were changed less than a year ago. What should I look out for on the muffler? The car doesn't sound any different and I haven't noticed any loss in power, although given how lightly I drive the car, I probably wouldn't even notice any reduction in power.

Thanks.

Loss of power would be the first sign. Rough running or trouble cranking would be another. Just the age of the car made me think it may have never been replaced. They do eventually get stopped up or rust out over time.

It still could be the gas.

Has traffic increased that you noticed' holiday weekend traffic?

Are you driving with the windows down any at all since it's "warmer".

What about the battery; weak batteries need to be charged more and the extra drag of the alternator could reduce mileage.

what about the fuel filter? has it ever been changed? it made a descent difference for me.

Thanks for the additional suggestions. The fuel filter in this car is in the tank and is not meant to be serviced - it was designed to last the life of the car.

The battery is only 2 years old and shows 12V with engine off, and 14V with engine on. It should be good for years to come.

I'm very conscious with the windows and A/C use. Usually just open a crack in the left-front and right-rear windows to get a good cross flow.

Nothing out of the ordinary traffic-wise. I make a lot of short trips <5km, so it's quite frustrating for me because I know the car can do a lot better. I've managed to cut down at least 33% of my driving by riding my bike this month. I'd love to get an electric assist bike, but they're still quite pricey and it'll probably get stolen real quick.

I'll have to have a closer look at the muffler. It almost certainly has not been replaced. How long do they usually last anyways? I recently had to change the starter contact points, so if there are any more major expenses, I might use it as an opportunity to trade for a 9th gen Corolla or an Echo for even better FE.

maybe its the changes in driving style that you think would improve mileage actually arent. have a scangauge?

could try driving more like you had in the past and see if mileage is affected up or down.

on the e-brake, if they happened to be draging, at a loss of 3mpg i'd imagine you would have smelt it when you get out of your car. you might jack up each wheel and give it a spin to eliminate it for sure though.

check engine light isnt on im assuming?

check how your tires are wearing, possible alignment issue...

thermostat operating at correct temp? acording to my scangauge, my old stat was running about 150, with the new 180. without some sort of scanner i wouldnt of known, the gauge in the dash reads virtually the same as before.

making more short trips? may have a stronger negative affect than improved driving style helps.

...and then back to a scangauge, assuming you dont have one. before ever having one, i could have tanks of gas vary by as much as 4mpg from one to the next, and not know what i did different if anything to cause it. with a scangauge i can see how my driving is affecting mileage.

My car does this when they go from Ethanol enriched winter gasoline to the straight gasoline. Find a gas station that is still using Enriched gas and see if it helps...

Shouldn't FE go up when switching from Ethanol "enriched" to straight gasoline? Is that the main difference between summer and winter blends? Since I only started logging fuel economy last summer, I don't have too much historical data to compare to.

Good idea. Think I'll give that a try this weekend. Thanks.

I don't have a Scangauge, but I can monitor a lot of the OBDII data (see my other thread on "possible Scangauge alternative"). Temperatures are normal and Check Engine Light is not on.