Hey everyone! New Suburban owner here. Its a 2012. LT Trim. Just bought it less than 2 weeks ago and LOVE IT! What a great vehicle! What I am not finding so great is the fuel economy.

It is listed as 15/21 (17 combined). I would be thrilled to be getting anywhere close to that! On our first tank of gas, we averaged 11.8 MPG! Currently on this second tank, the DIC is showing about 13.1 average. And slowly dropping.

Now you might be thinking we are hard on the pedal. Couldn't be further from the truth. We BABY that pedal. Think Morgan freeman from Driving Miss Daisy. That's us. I drive that thing sooo slooow and easy. I'll even use Cruise on side roads that go on for a mile or 2. 35-40 MPH zones.

We took a quick trip out to Stone Mountain (GA) which was a 60 mile round trip interstate drive. Got myself in the far right lane, set Cruise at 60-65 ish. Reset my average MPG to watch it on the highway. Got home and THAT TRIP trip averaged about 16 MPG. 90% highway miles.

I feel something is very wrong. Would LOVE to hear some ideas or suggestions on what I should look at or address. Thanks everyone!

 

Something is very wrong. 1st check the fuel manually don't rely on the DIC.
tune brakes dragging etc.

 

Thanks for the reply. Sorry, I should have been clear on that. I certainly did calculate manually the MPG on our first tank. The trip showed 296 miles driven on our first tank. At the pump we put in 25.1 gallons at our refill. 296/25.1 = 11.8

I guess I'll just take it in and have them look it over, but I've already had the air filter changed, the plugs checked. All seems well. Ugh!

Will be able to calculate our second tank in a few days. Any other ideas???

 

The DIC will always be about .3-.6 on the high side. My Tahoes both got 12-13 in town and 17-18 on hwy. You probably aren't going to get much better.

 

Do you have winter blend fuel in your area?

 

No winter blend fuel in the area. I hear and read that the 2500 Suburban is lucky to get 11-12. That's what I'm getting in the city driving like a grandpa nice and slow. Feel something has to be wrong. I can't fathom that I should be that far off of the 15/21 estimates.

 

I get 11-12 on my 2500, but I drive it like I stole it. The Blackbear tune is just too much fun. I get 15-16 highway.

Jack up each corner and spin the wheels, feeling for resistance. Maybe a caliper is hanging up.

I know a bad O2 sensor can make it run really rich. Not sure if that would go bad without throwing a code.

Have you checked your spark plugs and air filter? Replace as needed.

How do the tire treads look? Even wear on all 4 corners? Have the alignment checked. Excessive toe in or toe out really hurts mileage.

Check your tire pressure. I'm guessing since you're not getting a message on the DIC that they're ok, but it can't hurt to double check. Make sure they're at the max listed on the driver's door sticker.

Check the fuel rails for leaks. Does it smell like gas under the hood?

 

intheburbs points out some very good points, I would add that you could also have the alcohol level of the fuel read as suburbansr4me pointed out some blends can have a high alcohol content and this will produce much lower mpg.... if its available try a tank or 2 of marine grade fuel (100% gasoline) try a different gas station, and try using a tank of premium....
Keep in mind if you use any fuel additives they can increase the alcohol reading of the fuel....
All the above assumptions are based on you having a flex fuel engine...

 

Thanks guys! I've got some learning to do about alcohol content in gasoline! I'll certainly give all these suggestions a try and a look. i absolutely love this beast but the mpg currently is horrendous. Yes, this Burb is a FlexFuel model.

Will report back my findings! Thanks!

 

OK, so its been a few weeks and we've gone through 2 more tanks. The first tank averaged 11.8. The second got me 12.2 and the latest tank got me 12.0.

I'm a bit baffled by it all. Do not understand why I am so far off the 15 City MPG estimate. We have yet to have a good long highway trip to test out the highway MPG.

If any one has any suggestions on how to get a just a LITTLE closer to 15, I'm all ears! THANKS!