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Low Gas Mileage Cause

What’s causing low fuel mileage for 2013 Enclave with 36,000 miles? Getting 16mpg in town and 18-19 is advertised w/ 24 highway? Daughter has SRX with same 3.6 v6 engine getting 20 mpg in town (???). Is it air or fuel related?

Assuming that you and your daughter are checking miles per gallon the proper way driving habits, traffic , length of trips can all effect the MPG . Now if you are just going by the dash read out that could be off because they are not NASA calibrated instruments.

AWD or FWD (both vehicles)? That influences mileage. Also, unless you both drive the same circuit, comparing mileage is problematic. If you drive short trips and drives longer ones that can account for the difference, too, as can the level of traffic. I have a 4-cyl Honda Accord, and I get about 40 mpg at highway speeds, but in traffic, it drops to around 24. You might experience the same mileage drop if your mileage is during stop and go driving.

most low mileage situations are due to driving habits. Can you switch cars with your daughter for a week and check that mileage?

Second cause is driving conditions. short trips, city driving, lots of lights, etc.

Are there any error lights on the dash? Is the car in good mechanical shape? is it being maintained properly?

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Thanks for the quick replies. Its FWD and most of the driving is stop and go with lots of traffic lights. No error messages and the maintenance is excellent, just got back from dealership with their 346 multi point inspection, oil changed and tires rotated. Guess Volvo_V70 is saying the dash read out isn’t reliable …16mpg is the average mpg on the dash.

The most reliable way is to divide miles traveled by gallons of gasoline… I’m seeing 17/24 EPA estimates, so if you’re in mostly stop and go with lights, I wouldn’t be surprised if 16 is pretty close. Especially since it’s the summer and most of use run the A/C

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Next time you take an extended trip, reset your MPG readout and see what you get. I am not OCD about MPG, but periodically reset my gauge, if I saw a drastic drop would investigate but I would most likely see a check engine light first.

Two things that can cause low gas mileage are, a thermostat that’s stuck partially open, or a faulty coolant temp sensor for the computer.

If the thermostat is stuck open, it takes forever for the engine to reach operating temperature if it even does.

The computer will then run engine as if it’s cold all the time which means a rich fuel mixture which means more gas.

If the coolant temp sensor for the computer is faulty where it tells the computer that coolant never reaches operating temperature when actually does, the computer will think the engine is cold and run a rich fuel mixture which means more gas.


You state 36000 miles, has it always averaged 16 MPG?

The Enclave is considerably larger and heavier than the SRX, so I would expect the Buick to use more fuel. Driving habits and conditions also vary greatly from driver to driver.

16MPG for in city driving doesn’t sound low to me, it’s what I would expect to see from a car like that.


According to, they get the same gas mileage.

As others asked, is this a new issue, or did it always get these mpgs?

Thanks everyone for weighing in on this problem. To answer the question if the vehicle has always gotten 16 mpg, we really don’t know. It’s really never been an issue for me, until now.

Daughter is getting the Enclave as a “hand-me-down” and may not be able to use the car daily at 15-16 mpg. At one point, dropped to only 9 mpg per average mpg on the dash display that alerted me there might be a problem. Posted on CarTalk to see if anyone else is having low mileage issues with their Enclaves and, if so, what’s the cause.

We are investigating the faulty thermostat possibility someone posted as a potential problem.

Well, now I am confused. I thought daughter had a vehicle unless this is daughter #2 . If there are no vehicle payments and the daughter drives sensibly the fuel mileage in town should not be a major item.

And seriously , the fuel mileage needs to be checked the proper way to really know what this thing gets.

I’d have to look up the specs but my guess is that the Enclave is a good foot longer than the SRX, and I’m sure it’s taller. It’s got to be heavier, so it would makes sense to me that it would use more fuel, all other things being equal.

Understand the confusion, that’s daughter #2. Filled the car up and set trip odometers to zero so will get accurate mph very soon. I assumed the average mpg on the dash display was accurate and was interested in seeing if there were any ideas about what causing the low mileage per gallon. Appears there are many causes.

Thanks for your input Volvo_V70.

In the vehicles I’ve owned with fuel economy readouts, I found them to be very accurate, so I stopped doing the math myself. I always reset them at every fill-up.

The key to optimal fuel economy after eliminating mechanical issues is a well-calibrated right foot.

Driving habits influence mileage greatly. My wife and I drive the same car and I get about 3 mpg better mileage. If anything, I drive faster than she does , but I drove for a living for 55 years. I accelerate moderately up to whatever speed I wish to travel at and try to keep the car at that speed. I don’t rush up to a red light to stop and I try to time them so they atr green when I arrive. I read traffic better than she does and frequently pick a lane that is not going to stop.
To my wife a car is an appliance akin to a stove or refrigerator and she doesn’t want to thing much about driving it.

I try to keep quiet when she drives because I can’t cook.


Check to see if the tires are inflated to the pressure recommended on the placard on the left door pillar. Look at your temperature gauge and make certain that after the car warms up the gauge is in the normal range of the scale and not at the low end.
Comparing the SRX and the Enclave may not be a fair comparison, especially when driven by two different drivers. Could you reassign the daughter driving the Enclave to the SRX and the daughter driving the SRX to.the Enclave and see what happens to the MPG?
When my son was a teenager, we had a 1990 Ford Aerostar Eddie Bauer with a 4.0.liter engine. He consistently got better mileage than anyone else in.the family who drove the Aerostar. He always drove smoothly–no jackrabbit starts and smooth stops. He now has a daughter who is a teenage driver. I hope his driving skills are an example for her.

18 mpg around town would be fine, 2 mpgs lower is easily explained by driving habits. We have a similar vehicle that gets 16 when driven a little hard, 18 when driven more carefully.