Gas Mileage conundrum want the 21.5 back!!!

[ernzo]

92 ohv 4.0, stock, all terrain tires..

Drove from Colorado Springs Colorado to Lamar Colorado, 65 mph, no AC. Got 21.5....!!! 160 miles / 7.5 gal gas used. During the trip I could see that I was using less gas, you know how fast those gauges go down!!

Typically I get 14-16 avg. w/AC on. Around town and highway mixed no effort to save gas. Not a lead foot, just going the limit.

Best I ever got (until last week) was something like 18.

Since then, I am back to getting no more than 18..65 mph, no AC while drive 100% freeway only and really trying to save gas!

Difference? Octane? ( i typically get 87 on that trip I got the 91) How about elevation? Denver is 5280 feet and that trip I am closer to 3500 I believe. MAF sensor not liking the thin air? Oxygen sensor not liking the thin air?

Was I dreaming?

 

[Turdle]

All the above, plus the fact Co Springs to Lamar is Downhill all the way.

 

[billybob3358]

i would say the gas had some to do with it i only run 93 octane in mine and i can tell a noticable difference if i run 87 octane

 

[Willard]

I would say the 91 octane was doing a lot of that. The truck is designed to run on 87 octane, so it will be less efficient with 91.

 

[FirstExplorer]

Wind direction and speed? If the wind is at your back you will get better mileage.

 

[JTH1972]

I would say the 91 octane was doing a lot of that. The truck is designed to run on 87 octane, so it will be less efficient with 91.

Less efficient on a higher octane gas? How does that work?

 

[Turdle]

Less efficient on a higher octane gas? How does that work?

Higher octane gas does not have more "energy" in it, rather, it has more resistance to ignition. In other words, it takes more spark to light it off--

Since it is slower burning, higher octane fuel results in less efficiency. You only burn higher octane fuel when it is needed

 

[JTH1972]

so why do some vehicles run better off of a higher octane? My ranger ran better running 90 than it did running 87.

 

[Turdle]

Well, not knowing which engine was in your ranger-there are still several factors which come into play.

It could be the engine in your ranger was a higher compression engine which required higher octane fuel.
Also, as an engine ages, carbon builds up in the combustion chamber, and on the piston tops. This raises the static compression ratio. It can get bad enough to cause pinging when using low octane fuel.

Another thing that could come into play is the harmonic balancer and age. As the balancer ages it "comes apart" and the orientation of the 2 parts will become mis aligned, which will result in advanced ignition timing.

We are now getting way off topic I think. The main reason the great mileage was observed is the downhill grade from Colorado springs to Lamar, and, the prevailing west to east wind which is ever blowing there. I myself have experienced the same phenomenon several times making that trip.

Edit. as an experiment, fill up the tank in Colorado springs. Drive to Lamar. Fill the tank and record gallons to fill. Drive back to Colorado Springs and refill again. I bet 2 donuts this time, that the economy is way off on the return trip.

Edit 2 nevermind. Driving to Lamar is just not worth the trouble.

 

[ernzo]

Thanks for replies. I am now getting about 17 hwy. 65 mph, no AC around greater Denver. So i suspect downhill, good tail wind, bad math whatever, but I am still trying to get a respectable 18-20 hwy at 65 with NO AC. Think I ought to be able to do that, others here do.

 

[safn1949]

On my trip last year to Moab I got 19.1mpg at 65 mph on cruise.Now that took almost 3 tanks of fuel to get that kind of mileage because I don't drive it much and only around town.

Having said all that,I used to get 14-15 mpg around town and it was dead stock on that trip.I have since changed plugs,wires and installed a KKW intake and turbo muffler.The change is pretty dramatic,the truck runs much better with more power and acceleration.

I am now getting 16+mpg around town but have not had a chance to go any distance with it,I am going to guess I will get 20+mpg on a long trip.It's worth it just for the way it runs now.