2010 Z71 Fuel Consumption

I don't think the fuel gauge is linear. At least mine isn't. After 7 years I haven't figured out exactly how the instant and average mpg is calculated. My 01 Eldorado uses the fuel level to calculate mileage displayed by the DIC. It also seems to do a calculation on engine start. Most times if I park on an incline the car might lose 2-4 mpg between a shutdown and restart. I'm sure this is caused by the fuel level sender reading less whenever the car is parked inclined (nose in the air). As far as I know it doesn't use a flow meter for consumption.

The truck does use a flow meter. At least I think it does. I can display fuel rate used per hour, per min, fuel level (from PCM), fuel pressure, fuel rail pressure, fuel used/trip, and fuel remaining. These values are displayed via Torque Pro from PIDs on the Canbus. TP also has a scaling factor I can adjust to match the displayed average mpg (in TP) to measured mpg using mileage and gallons used from the pump every fillup. I don't hand calculate and adjust the mileage at every fillup; maybe every 10th fillup or so.

Parking the truck on an incline doesn't change mpg values on the DIC or in TP. So in the intervening 9 years between the Eldorado and the truck the mileage data has gotten more accurate and more sophisticated.

Ted

And one other thing. I have every reciept from every time I've bought gas. Have any of you ever seen one of the news stories about a station having bad gas and damaging X number of vehicles? The only way to protect yourself if you happen to get a tank of bad fuel is to have a reciept proving you got the bad fuel from so and so at whatever time. I guess with credit cards you could get a transaction statement but can you do that the same day you got the bad fuel?

If you used cash and got bad gas without a reciept you're SOL. Depending on the vehicle you could be out hundreds if not thousands of dollars. Yes I've heard of the tanker filling the diesel tank with gas. After flooding lots of stations pump your tank with water.

I used to use the pay at the pump with a card but since I got burned a couple of times from skimmers the Visa I use for gas will no longer approve paying at the pump. That's one of the dangers living in the boondocks. The only thing I mind about that is having to walk inside usually twice. My stenosis and COPD make that a hassle but I do it to get the reciept.

Ted

You can't depend on the gas gauge to determine fuel used or fuel left in the tank. I'm pretty sure there is more than 16 gallons in it when it reads half full. The only real way to tell how much you used on the trip is to fill up when you get back (at the same pump if possible). Even doing that you might be a half gallon or more off. That's why long term mpg figures are the most accurate. Short term doesn't account for minor speed differences or headwinds, etc.

GM fuel senders (like their speedometers) have always had a built-in non-linear weighting that shows slightly less than the actual amount of fuel. Just like the speeedometer reading slightly faster so they won't get sued if you get a ticket there's a little gas left so it's less likely to run out of gas. That has always led new owners to try to find the exact needle position when it runs out.

Driving style has much more impact on the mileage than many drivers suspect. When driving with the cruise control turned off I can get up to two more mpg. I live in hilly country so the CC is at a disadvantage. Allowing the truck to slow a bit going up a hill and making it up on the downhill side can stretch your mileage.

Ted