Anyone else have a change in MPG?

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by dadngt, Jul 14, 2012.

  1. dadngt

    dadngt Rockstar 100 Posts

    When I bought my truck used a couple years ago it would pull 18mpg about 200 miles on half tank with my regular driving habits. Then seems since fall last year my mpg has dropped to 14-15 range about 180 miles on half tank with same driving habits. Now I've noticed that I've been able to skip the gas pump a few days each week instead of having to go the same day every week. This morning I filled up & to my surprise I pulled 17mpg with the same driving habits. Which I know the summer fuel usually costs more because its susposed to be better, Could that be one reason my mpgs are up & down? Just wondering if anyone else has noticed this in their trucks.

    Still need to get a tune to get back up in the 19-20 range any suggestions?
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    All my vehicles respond to summer/winter fuel blends for the first month or so after the changeover I'll get different mileage, this new truck is no different than the rest.
    The only vehicle I've never had a problem with is the boat, I never use it in the winter so it's normally got summer blend fuel in it.
  3. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Summer/winter blends do appear to produce different mpgs; I wonder, is it the blends, or the air temps that make the biggest differences.

    The into of alcohol into the gas (10%, 15% mix) will lower the mpgs. Alcohol has around 10% less energy than gas, resulting in an appropriate reduction in mpg.

    You may also be suffering from a little wear and tear on the emission system. If getting close to needing a new set of plugs, changing the O2 sensor(s) at the same time will usually result in an improved mpg.
  4. Skippy

    Skippy Member 2 Years 100 Posts

    Yes, the summer/winter blends will result in different MPG ranges. For me, I lose about 1.5 to 2MPG with the winter blend. It "magically" gets restored around Memorial Day. This, incidentally coincides with the annual "they're raising the prices in anticipation of people going on vacation!" comments that usually occur when the summer blend kicks in. :)
  5. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    I definitely think the air temps play a significant role in the mpg differences...
  6. Sierraowner5.3

    Sierraowner5.3 Epic Member 5+ Years 1000 Posts

    i think air temp is the big factor here, in the summer its hot, plus you run A/C. winter its fairly cool/cold and you are on winter blend, ive seen the best mpg in mid to late fall, and again early late spring.

  7. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    Those observations match my own...
  8. GMCErica

    GMCErica Rockstar 3 Years GMTC Chick 1000 Posts Platinum Contributor

    I know that I dont have a pick up truck like everyone else does, but I noticed when I got my new exhaust, my fuel efficiency and economy went down. I don't use my air conditioner at all, as that uses up gas as well for me. But up here in the Great Canadian north, in the winter we plug in our trucks when it goes to -20 to -50C, or you wont start at all, and I notice my fuel efficiency is better in the winter when I cover my grille and plug her in. Normally, I get about 14 in the city 20 on the highway, combined about 17 or so. Just gotta watch the heavy foot with the exhaust, sounds so good though. I thought about CAI and scanners, but they don't do too much of anything... a few MPG or so, but not worth the extra 5 to me.
  9. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    The I6 engine needs a little back-pressure to help the mpg, the new exhaust removed most of that back-pressure. It's not a bad thing, just a little hit in the mpg.

    I switched to synthetic oil years ago for that reason. With the synthetic, it starts the same winter/summer without plugging it in.

    But.............a warm truck, just after you start it, can be a nice thing in the winter.:happy:
  10. GMCErica

    GMCErica Rockstar 3 Years GMTC Chick 1000 Posts Platinum Contributor

    Yea, I figured that with the new exhaust, the Envoy mpg are tailored to the stock one, and I talked to all my mechanics, truck friends and really, not that big of a difference, instead of going a week without filling up, more like 5-6 days.. I have a heavier foot now, LOL I like to hear it.. You know all about cold too brrr... But the trucks love a plug in... And my leather seats arent as cold.. LOL

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