"mr shmabs,I'm not sure what you need to be on enlightened as how a functioning fuel cap works,chee wheez,you have the internet at your finger tips,please lets not go there,as I have explained to this forum,is that I have replaced my gas cap, cause of a leaky seal,I am releasing vapors into the atmostphere and the enviornments.The leaky seal cap also looses fuel rapidly while driving and my mpg has really gone bad.Since replacing it,I have gained back my performance and mpg as per 4runner specs. I'm not going to reply you on how a gas cap works."
Quoted the above for gramatical humor.
Novasat,
First off, there wasn't any sarcasm implied, I was purely hoping for factual information tracked over a long enough period to prove your results to be valid. If you do in fact have that information, I would love to see it.
On another note, I can fully understand how vapor losses might affect your mpg, however I doubt it would be enough to make 2mpg difference, perhaps if you weren't running a fuel cap at all then you might see such dramatic results.
I did infact decide to follow your advice, and read on the internet (where everything is true) about RVP and how it pertains to gasoline, and the four most common types of evaporative emmision from the fuel system of a car.
There was some interesting research done in 2008 that concluded during fueling, the average american who fuels 1000 gallons a year would lose about 1/8th of a gallon per year to evaporative losses while re-fueling. Thats when fueling, with the cap off, not an apples to apples comparions with a faulty fuel cap, bus still a good read.
Effect of loss of fuel tank vapours on mileage - Motor Vehicle Maintenance and Repair Beta - Stack Exchange.
My tech additions to the thread:
My personal vehicle is a 1997 sr5 auto 4runner and has 265/75/16 duratracs (load range C) steel wheels, 4.30 gears, with sliders and t-case skid, and some additional extra weight. I am still able to achieve 20 mpg occasionally. The last time i tracked it was on the strech of highway 101 in Northern CA (mckinleyville) to southern oregon (coos bay). I used my gps to account for my speedometer and odometer innacuracy, and filled up at the same pumps during the same time of day. But let it be know, I was driving with mpg in mind. Around my town of residence, with lots of short trips and stoplights, 16-18 mpg is the norm.
The biggest difference i noticed with 265's was the weight, and i chose my specific tire because it was light (relatively) and will be ultimately swapping to aluminum wheels in the future to shave a few more pounds of rotating weight.
And I'm going to check the seal on my gas cap tomorrow, every little bit helps right?!?!
Thanks for the heads up novasat!
Back to the regularly scheduled thread.
Mike
