Jump to content

Inaccurate MPG readings?


Recommended Posts

So.. on Saturday, i accidentally reset my MPG meter thing. I was at 34.8 when i reset. After I got back on the highway, it began to return. Then, after a few miles, the meter began just skyrocketting. Went to 34.5...35, 35.1 and just kept going up. I was ecstatic! but then I noticed while I was in a light traffic, the meter would drastically decrease. Idle for not even 40 seconds and it had dropped nearly five tenths. :( I thought maybe it was a fluke thing. I had reached 40 MPG exactly by the time I hit Kings Dominion. On the way back, however, we hit some heavy traffic. I knew that my MPG would go down in traffic, but it dropped from 40 to 36 in less than 20 minutes. This doesn't seem normal to me. Before this, I could idle in traffic for more than 40 minutes and only drop about two tenths on the meter. Now today, when I checked OnStar Remote, it said my MPG is 36, but the meter in my car says 38.3... I'm so confused.

Anyone else encounter this problem?

Edited by Jeph Swift
Link to post
Share on other sites

It's normal on every car I owned with it. Your going to need to put some more miles on to get a more accurate reading. I reset mine every fuel up, it's pretty accurate once the tank is empty, usually within 1mpg with what fuelly calculates. Onstar I think calculates the lifetime average mpgs, which can't be reset.

Link to post
Share on other sites

Ah, okay. Thank goodness. I was so worried!! This is only my second car, and my first one from this decade. My first car was a 2000 Malibu and I had it for a few months. I could never estimate what MPG I was getting until I knew I was getting HORRIBLE Mileage. I was averaging 17... >.< I don't let my tank go below half.... I like knowing I have enough gas to get anywhere I am going. Thanks for your responses, guys. I just needed to know I wasn't crazy and my car was defective, lol. So, I should reset it after each time I fill up from half, or is it not worth it?

Link to post
Share on other sites

As what they said...reset every tank to get accurate results. Every tank but 1...has read within 1mpg of real world fillup math has showed. Our auto gets 46+on the highway...then her typical run around town stuff rips it down to the mid-upper 30s

Link to post
Share on other sites

On my first real tank with K&N and also fresh oil, right around my normal average of 42 indicated, I'll have more when I fill it. On my fuelly page, I started adding the car computed average in the notes if anyone wants to go through and see comparisons.

Edited by Greg_E
Link to post
Share on other sites

On my first real tank with K&N and also fresh oil, right around my normal average of 42 indicated, I'll have more when I fill it. On my fuelly page, I started adding the car computed average in the notes if anyone wants to go through and see comparisons.

I will start doing the same, and listing K&N

Link to post
Share on other sites
  • 1 year later...

The best gas mileage I have ever had (2013 Spark Auto) was on a long highway trip, cruise control set at 70mph for 300miles.> 42mpg using 93 Octane. Same trip at same speed using 87 Octane-> 38mpg. In town I get 29mpg with 87 Octane and 33mpg with 93 Octane. 87 Octane contains 10% Ethanol. 93Octane contains no Ethanol. Dollar wise I find it the same or cheaper to use the 93 Octane given the xtra mileage and power the 93 gives. I do notice more carbon in the oil with constant 93Octane use as the Ethanol burns a little cleaner. I have not done the math, but someone who is better at math may want to use these figures to see if it is a $$ benefit to use 93. I do notice that in city driving I have a noticeable amount more 'power' and on the highway I have more passing power at higher speeds.

Even though my gas mileage is not nearly as good as some have reported, my Spark seems to be one of the few with ZERO problems now at 48Kmi and a slightly higher top speed of 106mph with any gas. Built on 1/13 it seems to have had good luck all the way thru the assembly process and was properly manufactured with the correct parts. (I do notice that my car has a protective guard on the lower grille for stone protection for the AC components that are not installed on most of the 2013-14' I see & 'P-1' stamped on the head under the spark plug cover as well as on the original PCV hose before it was replaced and my mechanic says that could refer to 'prototype'??) I did have the PCV recall done at 45Kmi, but the old PCV valve had no issues at that point. Other than the 93Octane gas, I keep the tires at 45psi and use the Valvoline 'premium' 5W20 synthetic changed at 4,500mi intervals and really just drive the car fast as I can get away with on mostly highway including a 3,000 mile round trip Miami to NYC with lots of NYC city traffic driving and cruising at 80-90mph on the highway there and back with A/C on all the time...OK..'Nuff said.

Edited by Retired old Gearhead
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...