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2015 Nissan Sentra

Hello, Newbie here. After recent Nissan dealer full check and oil change, suddenly getting less mileage per gallon, lots less. No gas leak (odor or driveway evidence). Recent widow, husband was family car guru and mechanic. What should I look for? Any idea what the problem might be? Thank you all so much.

The first thing I would do is to check the tire pressure, as it may have been set much lower at the dealership than the inflation pressure that your husband used.

Has the weather recently turned colder in your area?
Have your driving patterns changed?
Is the Check Engine Light lit up?

Is the Check Engine Light on? An engine malfunction that lowers MPG would probably light it up or even make it flash (flash = stop engine now to avoid serious damage.)

Have you told the Nissan dealer you have noticed lower MPG? Winter, short trips, etc. mean lower MPG for everyone. A long highway run gives better MPG. MPG is more accurately measured when you buy a large amount of gas after many miles, rather than a small amount of gas after fewer miles. And multiple MPG calculations mean more than a single one.

Chances are there is nothing wrong and your lower MPG is an outlier. Good luck and please let us know what if anything is found.

VDCdriver, Thank you! 1. Tire pressure fine, I check monthly at Discount Auto, free service. GOOD ? because dealership was after last tire check, THX. 2. Yes, colder, though steady. 3. Driving pattern not changed (I’m age 72 yrs., grandchildren pick ups, grocers, errands, all within 15 miles, filled tank on the 6th, yesterday after grocers and Friday school pick ups, less than 1/4 tank, odd, odd). 3. No engine check lights showing. 4. Car parked on very slight slant, VERY slight (semi-rural area, cement driveway).
Thank you AGAIN! When I find the dang tire pressure tool, I’ll check today or tomorrow, back to Discount Auto. I just booked Your Mechanic online to do a 50-point check here, at my home. Is that not a smart move? Thanks.

That is an observation, not an MPG measurement. MPG is miles travelled divided by number of gallons used. It’s more accurate when you fill the tank to the same level every time, but that’s impossible to know precisely, so you add up the fuel over a few fillups and use the total miles travelled since the first of your fillups.

Thank you, Shanonia. No, I have not contacted the Nissan dealer yet, just figured all this out yesterday when I realized I was using more gas than I usually do now. No trips, not planned until summer. Yeah, I thought the lights would go on if fuel pump or other problem. Nissan receipt shows synthetic, which is what notes I took from husband before his passing indicate. Thanks again! I so appreciate these helps!

Yes, thanks again; you are so correct. I did not know how to phrase, and that was an observation. I calculated a loss of about 8-10% because I fill up only when gas warning light shows (also shows mileage left, though that is rarely correct). Price and gallons are always within $.50-$1.50/12 or so gallons. Tank is 13 gal or so. I like your equation better than my eyeball/receipt checks; thank you.

probably the cold weather.

Why are waiting until the low fuel light comes on. What are you going to do if it fails and you run out of fuel ? I think you should just refill when the needle hits 1/4 mark . And as others said check your miles per gallon the correct way.
I can’t remember the last time I saw the low fuel light come on.