Fuel consumption issue?

Good morning, JNENAY30,

Did you go to the dealer for the oil change?

Thank you,
Brendon

Hello JNENAY30,

My thought is that they adjusted your tire pressures. When it is fall or winter then tend to put them higher. In spring they tend to set them around what the manufacturer recommends which is on the label on the door. The reason for this is as the temperature decreases outside the tire pressure will decrease causing customers to come in because the Tire Pressure Monitoring System or TPMS for short recognizes this the pressure is below spec and turns the tire pressure light on.

Now as you drive your vehicle, the tire pressure will increase due to heat from the brakes being used and the tires rolling on the pavement.

In spring/summer months if it is set higher it can cause your tires to wear unevenly. So, they are more likely to decrease the pressure. With the decrease in pressure, fuel economy is affected because more of the tire is contacting the road and increases the resistance of it to roll which can decrease your fuel economy.

There is a label on your door jamb that will tell you what the manufacturer recommends for tire inflation for the best fuel economy, tire life and how the vehicle rides. In my opinion this is where it should be set regardless of the season.

If they did this you can check the label on the door jamb, (I will add a picture for you) and make sure they are inflated properly.

You should be able to view your tire pressures through your instrument cluster. It should tell you what each tire is at.

All tire pressures should be set and checked with the tires cold. But if a customer comes in say off the highway or has been using the vehicle in general the tire pressures will be higher than the specified value from the manufacturer because the tires are warmed up. So, it is possible they reduced the tire pressure, affecting fuel economy.

So, I would check the label and see what they are supposed to be at. Your vehicle should be around 34 PSI front and 34 PSI rear. But check the label on the vehicle as it depends on the weight of the vehicle and this label should always be followed.

The next thing I would check is the slip they gave you and see what oil they put in it. A lot of dealers put what is known as bulk oil in vehicles. Hyundai recommends either 5w20 or 5w30 but says for better fuel economy 5w20 should be used. So, if they put 5w30 in it will affect fuel economy.

**Note that this vehicle should be under warranty and bulk oil should not be used.**

The reason for this is the 5w30 is thicker when the engine is at operating temperature.

Most dealerships will have 5w30 in bulk because it goes in most vehicles and is cheaper for them.

So, I would double check your tire pressures and I would check the paperwork they gave you and see what oil was put in your car.

Please let me know if any other work was performed, like air filter replacement.

Let me know what you come up with and message me back so we can go from there.

Thank you,
Brendon

Hello JNENAY30,

You are most welcome and please do.

You're right, it doesn't seem like it would be the air filter either.

One other thing, any driving changes such as driving in more traffic or speeds under 55 MPH? Or are your driving habits the same as before you got the oil change?

Thank you,
Brendon

Hello JNENAY30,

Okay. I would go back and tell them you want the Hyundai oil. They should have it there because they would have to use the OEM part number when doing warranty work.

I don't know the ins and outs of Hyundai Powertrain Warranty but when I worked for Nissan, if a vehicle was under warranty, they would have to use and bill the Nissan part number for the oil, especially if a maintenance package that came with the car.

If there was ever a claim that could have anything to do with oil like an oil pump let's say. They will check and see if the OEM oil was used and could determine the warranty claim being paid or not.

I think you will be fine until your next oil change though, unless the fuel economy becomes worse. I would just keep an eye on your oil level and don't be afraid to take it in a little early.

When you do go my advice is to call and ask to speak to a service advisor and tell them you want to have an oil change, but you want to use the actual Hyundai 5w20 oil instead of the usual synthetic blend 5w30 bulk. Ask if the parts department stocks it and if not have them order it for your appointment. Chances are it's in stock. Have your vin handy as they will probably ask for it.

That way you will have a part number for the oil showing you used the correct oil plus hopefully better fuel mileage.

Let me know if I can help further and if any new issues start just message me back anytime.

Thank you,
Brendon

Hello JNENAY30,

You are very welcome. Happy to help!

Thank you,
Brendon