Improving fuel mileage isn’t matter of going to shop

Spike in gas prices can prompt some unneeded service, says Brian Turner.

Service counter consultants, especially at car dealerships, cringe every time there’s a significant spike in gas prices, 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.

“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 check engine light will come on.

If, for any other reason, the fuel mix fed to the cylinders is too rich, multiple oxygen sensors 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 the check engine light will shine. Even if one or more tires are low, which can affect fuel mileage, most vehicles will now let you know.

But that doesn’t stop many consumers from 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 inspect air filters for dirt, spark plugs for wear and do a diagnostic scan of the control computer that checks 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 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. 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 in the folds. If you see any amount of loose grit, change it. The few dollars you might spend on an air filter can be recouped in a few tanks of fuel.