Like you, my dad 88 yrs old gave me his 2002 2WD SR5, Ext cab 2.4cyl 3 years, with 29,000 miles on it, he bought it new and sealed in his garage driving it 1500 miles per year, its like new. I had just put 300,000 miles on my 95 T100 and loved getting a lower mileage Tacoma. I have been changing oil in my cars for 50 years. Mine holds 5.8qts with filter, like all the manuals I have read, I will check my dip stick to see if it looks likes yours. This may sound basic but, By chance do you buy oil in the large jug from Walmart, they are 5 qts, some other stores sell them in 4 qts capacity. If thats not the case, like earlier could it have gotten the wrong stick, have you always changed your our oil? this is fascinating delima.