MPG jump

[Torched10]

ive been getting 12.8mpg for 3 years--over trhe last week im now getting 17.1mpg as my average any ideas on why the jump Ive got 8,000 miles so no way avg could jump that high--havent fooled with settings--guess thats a good thing, but im wondering if something broken woner if its covered under warrarnty

[ilmor]

If your driving locations, speed, routes & style are exactly the same then as now, this would appear to be a computer glitch then or now. Warranty is 3 yrs / 36k.

[2012SilverSnake]

ilmor is probably correct, fill the tank, reset the mpg indicator, drive 100 miles or so, and refill and manually calculate and see how close they match.

[Torched10]

Thanks. It's kind of cool though telling folks I get 17mpg

[2012SilverSnake]

Is there a big difference in the '10s vs. '12s in MPG?

 

My stock '12 with 6k miles get 17 mpg all the time in combined city/ country roads/ fast shifting up to 70 MPH all the time. On the highway obeying the speed limits, it can get 23-24 if I keep from kicking in the SC and idle along in sixth which as we all know is hard to do.

[WJinLV]

Increase your tire pressure?

[Torched10]

nope havent changed anything--i dont do much highway driving, just local--thats why miles are so low--Ive never reset the mpg unit, but am now wondering how it does tha calculation--i did do a 100 mile trip mostly in 6th gear--so if it just does say the last 100 miles rather than the life of the car, the rise would make sense--But Im thinking its based on total mileage

[tturner770]

As I understand it, the mpg calculation is based on a rolling 500 mile average (your last 500 miles!) I've seen my average change by as much as 3 mpg by driving a couple hundred miles on the interstate -- from around 15 to over 18. My car is a 2010 also, and I usually average (on the display) about 17 mpg. I have been told that the computer generally underestimates what your mileage really is. I haven't ever checked the mileage by calculating it myself to see if that is true. It has always seemed kind of funny (that's funny - Ha Ha!, not funny - odd) to me that when the low gas messages comes on - "50 miles to empty" - I still have almost a quarter of a tank of gas!

[kawwy600]

To my knowledge if you have never reset the computer for mpg it would display the average for the life of the vehicle. Is it possible someone had access to your car and they reset the mpg estimator? (valet, kids, wife...)

[Torched10]

Nope. I'm the only one No valet for this car. I drive my sts v for that

[ingram4868]

FWIW, I have always gotten 17-19 MPG.

[Bill Hamilton]

I've been tracking all my fuel fill ups over the last two years here: http://www.fuelly.com/dashboard/ Mine is a 2011 model and the EPA sticker said 15 to 23 mpg. I usually exceed both of these numbers. I'm usually at 17+ in normal driving and then have done as well as 25.7 mpg on a trip. I'm usually closer to 24-25 mpg doing legal + 9 mph speeds. Even running 80'ish I get 20+ mpg .. you know when you're in a hurry (LOL). Over my last 78 fill-ups and 14,000+ miles I'm averaging 19.1 mpg. I'm amazed at the fuel economy the car can deliver if driven normally. I also have a 1970 Mach 1 with 351C-4V and track it's fuel usage on this same site and I'm normally at 12 to 13 in normal driving and can get 20+ on the highway. My 1970 Mach when new was a 12 to 16 mpg vehicle. It now has a modern T-5 five speed with overdrive which really helps on the highway but not so much in city driving .

[Torched10]

I generally ride around in 3rd gear on local roads and luv the sound if the sc. Hence my low Mpg. Have 2 other cars the are worse. A 65 gto tripower and a 2011 ext

[WJinLV]

I got 17 MPG on a 100 mi round trip this weekedn, but I was heavy footed up to 130 a few times on an empty hwy.

[Bill Hamilton]

Last weekend I drove up to Kershaw, SC (CMP race track) to watch the Detroit Speed series going on there. Really cool series and I got lot's of neat photos ( https://www.facebook...=1&l=d94bc22a3a).

 

Anyways going up I drove "normally" (80'ish as traffic allowed) and got 21.1 mpg. On the way back I filled up right before getting on I-20 and set the cruise at 70 mph. I had to tap the brakes a couple of times to slow for traffic and passed two different 18-wheelers but basically stayed in the right lane and out of the way and did the posted limits all the way back to Charleston, SC. I nearly had my doors blow off a few times as SUV's, Toyota Prius', and nearly anything else you can think of rocketed past me doing 10+ mph at least.

 

When I turned off the interstate and refueled, the in car mpg gauge showed 24.9 but calculating it manually and using my online tracker (https://www.fuelly.c...tang?fu=2936123) showed I actually got 26.1 mpg. Pretty amazing for a nearly 600 hp car.

[Boidster]

My car's about 15 months old and maybe 7,800 miles. For the first couple thousand miles, it showed MPG in the low 15s (I reset the counter a few times and let it go for a few hundred miles each time). Then, last summer, it jumped up to about 17. I drive 50/50 city/highway, and I'm not particularly heavy footed though all onramps must be taken at full throttle, naturally. Remember to slow from 100 to 60 when merging!

 

The only change was the brand and viscocity of oil. I won't mention the name, as this isn't a plug for an oil company. But unless the computer decided to change the mixture at that arbitrary point, the oil is the likely culprit.

 

Over the winter, mileage dropped about 1MPG; I have yet to drive the car enough in warm weather to see if it's going to tick back up. I guess the colder, denser air in winter allowed more fuel to be in the mix, giving me more HP on onramps, but also slightly lower MPG. Tire pressure probably also plays into it.

 

And but so anyway, 12.8 MPG seems awfully low for normal driving, but if you're stomping on it a lot (racing your wife's 'vette?) it's probably reasonable. And the 100-mile drive in 6th probably averaged low- to mid-20s so if the rolling miles for the MPG calculation are 500, that could move the number quite a bit. A little back of the envelope math says that if you have 400 miles at 13MPG and 100 miles at 25MPG, your overall average will be 15.4. Was it 100 miles both ways?