Fuel mileage variation

[Tiny]

Had a little road trip from Indy to St Louis this weekend. On the way down, set cruise at 72 in 6th (MT) as much as I could. I got 19.9 mpg according to the trip meter. That's decent for my set up. There are some light hills but really nothing to speak of elevation changes. Just as much downhill as up really. Weather was mid 70s and rained off and on no wind noticeable. Drive home this morning, pretty much exact same conditions. I could barely manage 16mpg. I for the life of me cannot figure out why such a difference. Oil is less than 1000 miles old. Recently change air filter. Nothing I could find doing a cursory walk around and peak underneath. Any ideas? Slight variation seems reasonable but 20+%?

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[Gren71]

There are just a TON of variables for fuel efficiency. One trip isn’t enough to really get a picture of what you are getting, or figure out ways to make to better or worse.

here is a bit of an experiment I did while back just as an example.

https://www.jeepgladiatorforum.com/forum/threads/mpg-experiment.53810/

 

[Jefe1018]

Your mileage may vary, literally.

I’ve found my computer to be on the money about 80% of the time, but it can be off by quite a bit as it takes certain factors into consideration, which may have little affect on actual mpg.

Were you in traffic one way and alone the other? Having another vehicle in front of you breaking the wind for example makes a huge difference in the energy needed to maintain speed.

 

[Rusty PW]

Elevation change. You are running down hill to St Louis from Indy. Then going up hill back to Indy. We go from south of Pittsburgh to Denver on I70 twice a year. I get the same mileage thing as you. Running down hill to the Mississippi River, lowest point,. Once there, it's up hill in either direction.

 

[kevman65]

Elevation changes, wind direction, fuel.

Not all gas is created equal. If you went bargain shopping for gas and bought an offbrand, that's a big difference.

 

[Tiny]

Just seemed odd it'd be that drastic. I really didn't notice any wind and traffic was pretty open both ways. Gas was a tank full of whatever kroger pumps to start and then shell for subsequent fill up. I noticed even on flat stretches the real time mpg (watched it the whole way) still stayed at about 16. Who knows I guess!

 

[Jefe1018]

Just seemed odd it'd be that drastic. I really didn't notice any wind and traffic was pretty open both ways. Gas was a tank full of whatever kroger pumps to start and then shell for subsequent fill up. I noticed even on flat stretches the real time mpg (watched it the whole way) still stayed at about 16. Who knows I guess!

It's a Jeep thing?

 

[Tiny]

It's a Jeep thing?

The answer was in front of me the whole time LOL

 

[Gvsukids]

The answer was in front of me the whole time LOL

Will it be the last Jeep you'll ever own?

 

[redriderjf87]

A small headwind could be significant, with the overly tall diff ratio.

 

[ShadowsPapa]

Elevation change. You are running down hill to St Louis from Indy. Then going up hill back to Indy. We go from south of Pittsburgh to Denver on I70 twice a year. I get the same mileage thing as you. Running down hill to the Mississippi River, lowest point,. Once there, it's up hill in either direction.

We got better coming back from Colorado Springs to Iowa - it was fun to watch the elevation change as the hours passed. Yes, it matters. I used to joke with my wife when she went to Florida with a quilting friend - I told them it was going to cost more coming back home. I was only slightly kidding.

Just seemed odd it'd be that drastic. I really didn't notice any wind and traffic was pretty open both ways. Gas was a tank full of whatever kroger pumps to start and then shell for subsequent fill up. I noticed even on flat stretches the real time mpg (watched it the whole way) still stayed at about 16. Who knows I guess!

Oil miles isn't going to matter unless comparing oil with 500 miles to oil with 7,000 miles..........
Wind - we're talking a brick with a windshield that acts as a jib on that thing, so 5 mph matters.
If the leaves on the trees twitter at all, it matters.
Air density matters - what was the barometric pressure, humidity and so on? Denser air offers more resistance.
All kinds of factors could have added up to make that difference, but it's going to matter more on a Jeep Wrangler or Gladiator than a Camaro.

 

[Hootbro]

I drive the same basic route to and from work and get high 18's going to work and low to mid 17's coming home. Touching on what @Rusty PW said, it never is truly the same going both ways. Even if the same temperature, humidity and air density levels can play a role in addition to different elevation and road level grade can play a factor.

 

[NachoRuby]

I get 15 on the way to work andd 20 on the way home every day. It's normal. Elevation changes.

 

[Mr._Bill]

My Dad used to tell us about when he was a kid and had to walk to school, uphill both ways.

 

[Rusty PW]

My Dad used to tell us about when he was a kid and had to walk to school, uphill both ways.

Reading the new posts. I was thinking the same thing. LOL

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