Money doesn’t always improve fuel mileage
Taking car to the shop for just a fuel economy problem can be a real waste of time and cash
Service-counter consultants, especially at car dealerships, cringe every time there’s a significant spike in prices at the gas pumps, such as the recent one from Hurricane Harvey.
They know phones will be ringing with complaints from customers about the fuel mileage on their pickup trucks and SUVs, and even some smaller vehicles. No, the usage didn’t change since before the price jump, but still these advisers will be inundated with demands for some type of fix, because all those vehicles aren’t getting what their window stickers promised.
“There must be a fix!” is the rallying cry from drivers hoping for a miracle software update or hidden fix known only to those in the know. But for just about anything built in the past 10 years, taking it in to the shop for just a fuel economy problem can be a real waste of time and money.
For all modern fuel-injected engines, the efficiency of each combustion cycle is continually measured by on-board computers. If a spark plug, its wire, or coil are failing bad enough to affect fuel economy, a misfire code will be set and the infamous check-engine light will come on.
If, for any other reason, the fuel mix fed to the cylinders is too rich (meaning too much fuel), multiple oxygen sensors mounted in the exhaust system will sound the same alarm. If it’s idling too high or taking too long to warm up in the morning — you guessed it — the check-engine light will pop up on the dash. Even if one or more tires are low on pressure, which can affect fuel mileage, most vehicles will now let you know through an instrument-panel warning.
But that doesn’t stop many consumers from making an appointment and taking their ride in to the shop. When a tech is presented with a vehicle and a repair order request to check for poor mileage, he or she will dutifully inspect the likely culprits. Air filters will be checked for dirt, spark plugs for wear and a diagnostic scan of the engine’s control computer will be completed to check for any trouble codes or possible software updates.
All of this takes time, and as the adage goes, time is money. If the vehicle in question is under warranty some, but not all, automakers will allow the dealership to claim this type of inspection for reimbursement.
And if it’s beyond the terms of the warranty, you can expect an invoice ranging from $50 to $150, depending on the shop’s labour rate. Of course, that would buy a tank or two of fuel.
About the only situation a vehicle’s computer can’t always detect is a dirty air filter. For an air filter to trip a check-engine light, it would have to be so plugged as to severely restrict incoming air. But a filter that is less contaminated will still affect fuel economy.
Inspecting an air filter is a rather easy DIY job and the access process is covered in all owner’s manuals.
If you’re not sure if your engine’s air filter is dirty enough to replace, spread the paper folds open a bit with your fingers to check for any grit or dirt down in the folds.