I was curious as I accidentally filled one of my trucks from a gas can to where the gas was almost up to the gas cap. I would have spilled gas had I not been paying attention. I know they always say not to top off at the gas station. What harm could this do to the truck?
I live a ways from town and use one of my gas guzzler trucks to move firewood. Since it would burn several gallons driving to town and back to fill it up, I usually just add a gallon or two at a time after using it. I drive the 50+ mpg Geo Metro to town most of the time and just take the empty gas cans with me when I am about to fill it up and fill them at the same time.
Since the gauge doesn’t really move when only a gallon or two has been burned, I don’t have a good way of knowing exactly how how much gas it can take. There are times where I have a lot of idling in 4WD low range and this burns more gas than you would expect.
Anyway, I was just wanting to see how bad of a thing to do this is. If bad, I may just add a gallon when the gauge starts to drop and repeat as needed. I like to keep all my tanks close to full so there is less air space for oxidation and condensation to occur and also I am currently concerned the the situation in the Middle East could take a dramatic turn for the worse anytime.