20 MPG

Geo-TH,In · Apr 27, 2011

Normally I only get 18 mpg with my 2007 GMC work truck. Last fill up I got 20. We have had nothing but rain and cool temps. Could this be the reason for my increase in mileage? Or could it be where I purchased the gas?

old · Apr 27, 2011

Temperature, wind, humidity and barometric pressure all factor into how good or bad your MPG is. Also things like tire pressure and having a dirty car/truck can affect MPG

Uncle Ernice · Apr 27, 2011

A dirty car??? Come on old, How much dirt do you think it would take to measurably affect the fuel mileage of a vehicle. Good grief.

old · Apr 27, 2011

Yes dirt. Was proven many years ago a dirt car over a waxed car got worse mileage but ya by so little it would take 1000 mile or so to notice it much but yes a dirty car gets worse MPG

Wilson · Apr 27, 2011

Old friend I seem to get about 5 per cent better milage with shell regular also the 10 cents per gal discount from kroger - jcey food stores honered at shell is good also

rustyj14 · Apr 27, 2011

Here in our area, we have a grocery chain that has the "fuel perks" thing, where you buy the groceries, and get a discount on yer gasoline purchase. Only problem eith that--the store is 12 miles away, so you burn up any savings ya might get from buying yer groceries there, and gas too.
I figger, i'd might as well drive a mile and a quarter, and back, and not burn near as much gas as i would driving 24-25 miles to get it.

jbp · Apr 27, 2011

Old is right, otherwise why did the Air Force wash their airplanes? Makes them slip through the air better with less surface turbulance and more lift.

Joe

Uncle Ernice · Apr 27, 2011

I got some magnets I can sell ya to go on your gas line and align the molecules too... And a gaget to make the air swirl going into your carb.
Driving with bigger tires in the back will make you go down hill all the time too, right?
Thanks for the chuckle...

MSM · Apr 27, 2011

Don"t know where you live,but they may have switched away from winter blend gas. Here in Md. they have a cocktail mix that they require for winter driving which usually costs me 2-4 mpg. Both of my wife"s cars and my pickups have seen an increase in mileage in the last couple of weeks.

Uncle Ernice · Apr 27, 2011

The air force also paints rocks...
I will check my mileage next time I am driving at Mach 2...

36 Coupe · Apr 27, 2011

Larger tires will increase the gear ratio.It reduces the engine rpm at the same road speed.

Uncle Ernice · Apr 27, 2011

I have seen mileage decrease with larger tire size too due to the increased rolling resistance of a larger diameter tire or higher rear end ratio. Seen it drop way off too due to too small a tire having to be spun faster to cover the same distance.
Danged if them engineers at the car manufactures might do more than guess soemtimes!

john d · Apr 27, 2011

I drive a 2010 Chevy 4wd pickup. In winter weather when the temp drops to 10-15 degrees at night, it takes 2-4 miles before the transmission temperature gets up to 80 degrees or so. As the weather has warmed up over the last month, my trans temp is much warmer during normal driving, and mileage has gone back up to where it was when I bought it last June. Winter blend gasoline is probably part of the equation, also.

Anonymous-0 · Apr 27, 2011

DIRTY car ? O h ,yeah,it has been proven, yes /...and air up the tires too , just listen to the current prez , and we wiil save us a bunch , yeah ,, that is the answer ....

Sid · Apr 27, 2011

I wonder. Did that rock painting thing have anything to so with global warming?

showcrop · Apr 27, 2011

That's why I keep my tractors waxed, especially the pullers.

old · Apr 27, 2011

LOL well back in the 70s when there where the long gas line a company did a wide tunnel test and they did in fact fine a clean waxed car got better MPG then a dirty one did

old · Apr 27, 2011

What can I say there was in fact a wind tunnel test done in the 70s that did in fact prove a dirty car got less MPG then a clean one but then some people do not look

old · Apr 27, 2011

Get a clue guy. My 1980 Chev has 307 gears in it and I get 17 MPG out of it. I know a guy who has the same truck with 340 rears and he gets 12mpg but if he runs 16s instead of 15 he does get it up to around 15 so what goes on here if bigger tires do not help?? But again it gets to the point of going to far. Engineers olny do as they are told to do that is why it takes a college degree to work on a car and you pay $100 per hour to fix a broken light bulb that in turn takes an hour to replace because you habe to remove 10 parts to get to it

gene bender · Apr 27, 2011

You must not know about living in the boondocks where it isnt hard to get a lot of extra wt when its muddy.

MSD · Apr 27, 2011

Did you not see Myth Busters last week? They put clay on a car and tested the mileage. Then they put dimples in the clay to resemble the dimples in golf balls. Increased their mileage but somebody else probably remembers by how much. 2% I think.

farmer boy · Apr 27, 2011

The only thing that has ever helped me for better mileage is a well tuned engine and driving with a light foot. I can"t hardly afford driving a 20mpg vehicle anymore. Gas is 4.90+ a gallon.

kyhayman · Apr 27, 2011

Or carry as much junk as I do. I traded a truck a month ago and weighed it before and after cleaning, took 1700 pounds of stuff out. Everything from broken rake teeth, wet hay, and tools to shirts coats and a host of other dirty laundry.

Bob · Apr 27, 2011

"I have seen mileage decrease with larger tire size too due to the increased rolling resistance of a larger diameter tire "

PLEASE post something to substantiate THAT claim!

Uncle Ernice · Apr 27, 2011

Put a set of them 22" wheels on your car and see what it does to the mileage!

Bob · Apr 27, 2011

I'll try again... HOW do you explain... "increased rolling resistance of a larger diameter tire"?

MarkB_MI · Apr 28, 2011

Probably not. Cooler air temperature makes the air more dense, while high humidity makes it less dense. So those two factors are actually working against each other. The reason is probably much more mundane.

Going from 18 to 20 mpg is an 11 percent increase. That's a lot. Car manufacturers go to great lengths just to get a tenth of a percent. So the first thing to suspect is how you made your measurement. Do you go by the odometer and how much fuel it took to fill the tank, or do you use the vehicle's computer, resetting the average each time you fill up? The former method is wide open for errors. (I'm not saying the vehicle's computer is inherently accurate, but it is inherently CONSISTENT.)

If you normally gas up with 20 gallons, and you filled your tank fuller by two gallons the first time you refuel than the second time, that would give you your 11 percent. If the station you use is on a hill, and you used different sides of the pump when you fueled, that could account for most of the difference. Also, different people fill the tank to different levels; some try to get as much gas as possible in the tank while others stop as soon as the filler trips. And how fast you fill the tank affects how full it gets because the tank inlet is designed to trap air in the tank.

Anonymous-0 · Apr 28, 2011

The probably ran out of corn alcohol.

Karl in MD · Apr 28, 2011

My dad was in the Army Air Force in World War II, and the good crew chiefs kept their planes clean and waxed. Dad said you would gain about 5 knots with a clean airplane and cut your fuel burn, also.

mkirsch · Apr 28, 2011

(quoted from post at 21:22:14 04/27/11) "I have seen mileage decrease with larger tire size too due to the increased rolling resistance of a larger diameter tire "

PLEASE post something to substantiate THAT claim!

Larger tires are also wider and heavier. They have a larger contact patch with the ground, and in the case of pickup trucks, they also tend to have more aggressive tread patterns.

Hence, increased rolling resistance.

Regardless, a taller tire will require more torque to turn it. That is simple grade school physics that you can take to the bank.

There's a "sweet spot" for each vehicle where the tire height best matches the drivetrain (engine, transmission, differential) and driving conditions for best efficiency.

Whether you go larger or smaller in tire size, it causes the engine to operate outside its peak efficiency RPM range. Too large a tire causes lugging and downshifting. Too small a tire causes the engine to "over-rev."

Bob Kerr · Apr 29, 2011

I have a 49 Chevy 3600 3/4 ton with a 216 engine and a 457:1 rear end. When I got the truck back in 1977 it had the optional 15" wheels. Almost every one of those 3/4 tons had the optional 15 wheels because tires were expensive after WW2 because the japanese trashed a lot of the rubber planations in SE asia when they retreated. I later found out in a factory parts book that 17" split rim wheels were standard but very few buyers wanted them! Took me a couple years to finally find a set as they are really scarce. I got a set off a 57 Chevy 4 wheel drive 3/4 ton. When I put those 17s on the city gas mileage acually went down a little, but on the highway it went way way up! Top speed also went up and I could acually drive it down the interstate without getting rearended. I was never able to get the mileage recorded as an oil line cracked where it passed through the water jacket and antifreeze got in the oil and ruined the rod bearings which I haven"t fixed yet(14 years ago now). 15" city mileage from what I remember wasn"t bad at about 17mpg. After that I estimate it went down to 14mpg or even less. Took more throttle to get those big wheels 750-17 tires spinning. Once they were spinning the little 216 had just enough power to keep them going and the estimated mileage went up to around 25-27. It became a totally different truck after the 17" wheels were put on. It did so well I drove that truck on long road trips! Come to think of it, with gas prices like they are I better get working on it again!

Lyndon - AB · Apr 29, 2011

(quoted from post at 14:19:39 04/27/11) Normally I only get 18 mpg with my 2007 GMC work truck. Last fill up I got 20. We have had nothing but rain and cool temps. Could this be the reason for my increase in mileage? Or could it be where I purchased the gas?

When my '03 Cavalier Z24 went from 40 to 45mpg, I thought it was great. Until I checked the oil and found out it slurped half a gallon out of the crankcase. :? Funny though, it stopped and never burned a drop since. Hasn't done better than 39 mpg since either. Don't know which is cheaper any more though, fuel or oil! :mrgreen: :roll:

20 MPG

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